[From the U.S. Government Printing Office, www.gpo.gov]
Zonev c.2. 7 C~~ ~~~~~~~~~~~~~~~~~~~~~VA TECHNICAL REPORT NUMBER 2 NOVEMBER 19761 DELAWARE COASTAL MANAGEMENT PROGRAM AN ATLAS OF DELAWARE'S WETLANDS AND ESTUARINE RESOURCES Technical Report Number 2 Delaware Coastal Management Program November 1976 Property of CSC Library Original Manuscript Prepared by: Franklin C. Daiber Oliver W. Crichton Lawrence L. Thornton Gerald L. Esposito Karen A. Bolster David R. Jones Thomas G. Campbell John M. Tyrawski I College of Marine Studies }k~~~~ ~~University of Delaware Newark, Delaware T E IzFeRNATiN CENTER (, $ fF, F:A'kFN~J OF COMMERCE NOAA June 30, 1976 ', Ol, :F'tvl( CS CENTER 223~ SC l1. el HOPON AVENUE ChAhLKS.TON, SC 29405-2413 Under Contract to: Delaware State Planning Office Thomas Collins Building Dover, Delaware 19901 This publication is financed in part through a federal grant t t___ from the Office of Coastal Zone Management, NOAA under the P- s, provision of Section 305 of the Coastal Zone Management Act -' . of 1972 (Public Law 92-583). .i so TABLE OF CONTENTS Page Acknowledgements . . . . . . . . . . . . . . .... Introduction .. . . . . ............. Section I - Wetlands General Principles of Wetlands Ecosystems . . . . . . . .. 1 Wetlands and Estuarine Productivity .......... 10 Edaphic Algae. . ............... 12 Phytoplankton. . . . . . .......... 13 The Emergent Grasses . ............. 14 Animals and Wetlands . . 20 The Relationship Between Wetiands and'Estuarine Water Quality . 29 Silt . .. .. .. .. .. .0. .. .. ... 29 Sewage...... . . ........... 31 Heavy Metals ........ . . . . ..... 34 Oil Pollution . . . . . . . . . ........ 37 Thermal Pollution . . ............. 42 Pesticides . . . . . ..42 The Role of Wetlands in Estuarine Hydraulics ....... 44 Definition and Classification of Wetlands ......... 47 Definition of Wetlands . . . . 47 Predominant Plants of Delaware's Wetlands . 53 Wetlands Classification System . . . . . . . . . . . . 71 Wetlands Zones and Properties . . . . . . . . .. 71 Wetlands Zones and Associated Vegetation . . . . . . . . 74 Zone I, Cordgrass Marsh . . . . . . . . ... 76 Zone II, Salt Meadow Marsh . . . . . . . . . . . . 78 Zone III, Salt Bush - Salt Meadow Marsh . . . . . . . . 80 Zone IV, Reed Grass Marsh . . . . . ........ 82 Zone V, Transition Marsh . . . . ...... 84 Zone VI, Arrow-Arum - Pickerel Weed Marsh ....... 86 Wetlands Atlas (Maps) . . . . . . . ........ 88 Wetlands Drainage Areas. . . . . . . . ....... 115 Results of Mapping. . . . . . . ......... 115 Discussion of Drainage Areas . . . .... 121 Survey of Delaware's Wetland Drainage Areas . ...... 125 Wetlands Destruction. . . . . . . . 165 Dredqinq and Bulkheading . . . . . . . 165 Definition and Description . . . ......... 165 Impact .. .. .. .. .. .. .. .. ...167 Beneficial Effects . . . . . . . . . . . . . . . 171 Discussion. . . . . . . . . . . . . . . . . . 171 Factors Which Could Mitigate . . . . . . . . . . . . 172 Spoil Disposal . . . . . . . . . . . . . . . . . 176 iii. TABLE OF CONTENTS (continued) Page Effects of Spoil . . . . . . . . . . . . . . .. 176 Beneficial Effects . . . . . . . . . . . . . 182 Recommendations . . . . . ......... 182 Impounding . . . . . . ..........*. 185 Definition and Description . .......... 185 Effects . . . . . . . . ........... 186 Ditching . .. .. .. .. .. .. .. ....195 Definition and Description . . . . . . . . . . . . 195 Adverse Effects. ............... 196 Vegetation Type ................ 198 Beneficial Effects . . . . . . . ........ 199 Mitiqating Measures . . . . . ...... 200 Conclusions and Recommendations . . . ... . 202 Waste Disposal.. . .......... .205 Solid Waste Disposal.. . . . . . . .... 206 Liquid Waste Disposal ..... 208 Residential, Commercial and industrial Deveiopment .. 211 Marinas .. ..............224 Recommendations . . . . . . . . . . . . . ... 232 Agriculture . . ................ 233 Sediments . . ................ 233 Nutrients . . ................ 235 Pesticides . ................. 236 Environment Parameters . . . . . . . . 241 Dissolved Oxygen and Its Relationship to Estuarine Organisms . . 241 Temperature and Estuarine Organisms . . . . . . . . . . 254 Turbidity . . . . . . . . . . . . . . . . . . . 267 Salinity . .. .. .. .. .. .. .. .. .. 268 Tidal Flushing . . . . . . . . . ........ 277 Toxic Materials . . . . . ... . . . ...... 283 Section II - Estuarine Resources Introduction to Estuarine Inhabitants - Life Histories .... 285 The "Typical" Fish . . . . . . . . . . . . . . . 285 Skates . . . ..............289 Atlantic Sturgeon ................ 297 The American Eel ............. 303 The Herrings . ............... 309 Atlantic Menhaden ................ 317 The Bay Anchovy ................. 323 Freshwater Catfishes ............... 329 Mummichog ..... ..... ..... 335 Striped Killifish .......... 341 Atlantic Silverside ............... 345 The White Perch ................. 351 iv. TABLE OF CONTENTS (continued) Striped Bass I I. I I I I . I I . I . I I I I . I 355 Winter Flounder. I I I . I I I I . I I I I . I I I. 359 Yellow Perch.. . I I I I . I I.I. . I. I . . I I .365 Bluefish I I . I I . I . I I I I . I I I I . 373 Atlantic Croaker' I 381 WeakfishI. IIII. IIII. .III.III387 The Northern Puffer . IIII. . I.I.IIII.393 Summer Flounder I. . I I I I 399 The Hogchoker . I I. . I.403 Jellyfish I. . IIII. I I II. II. I . 409 Comb Jellies . III. . III. . I. II..I.I..415 The Hard ClamII.II.I . . I I., I I I I. 417 The American Oyster I I II. IIII. II II. I425 Oyster Drills I I I . I I I I . I~~ 431 The Blue Crab I. . IIII. I. 437 Zooplankton I I I . I I I I . . I I I . I I I. . 443 Sources for Environmental Requirements I I I. . I I . I . I 467 GeerlReferences for Fishes I . I .I 47 Introduction to Aves - Life Histories I I I . .... 475 The Great Blue Heron I . I I..I.I.. I.II. . I .II479 Cattle Egret I . I I I I . I I I I . I I I I . I I 484 The Snowy and Common Egrets. I . I I I I . I I I I . I. 488 The Green Heron . I. II.IIII.IIII.II490 The Black-Crowned Night Heron I I . I. I. II. I .II. 493 Snow Goose .IIII . I. . I I I I . I I. .. . I 499 Black Duck I I I . I I . . . . III. IIII. 505 Pintail I I .. I . I I I . . III. IIII. 508 Green-Winged Teal . IIII.IIII..I.II.I . ... . . 510 Wood Duck..I .. . I . . I I I I . I . . I I I 512 S coters I . I I I I . I . I I . IIII. II516 Clapper Rail I I *. I I I . . I I I. . IIII. I519 King Rail.. . I I . I I I I . I. . II II. I . 521 Virginia Rail.. .. I I . I I I I . I I. . IIII. 524 References for Shorebirds and Waterfowl . I I I I . I I I I 527 TABLES Table IA List of the Common and Scientific Names of Those Species of Plants Used to Define and Delineate the Wetlands of the State of Delaware According to the Wetlands Act of 1972 I 52 2 Area of Wetlands Contained in Each Drainage Area I I I I . I 118 VI TABLE OF CONTENTS (continued) Table Page 3 Percent Composition of Wetland Drainage Areas by Vegetative Zones in 1973: Percent of Wetlands Lost to Construction or Impoundment Since 1938. . . . . . . . . . . . . . .119 4 Total Attendance at the Five State Parks in the Coastal Zone (1965-1970) ......... 5 Sales of Boat Licenses in Delaware j1962-i970) .. .. 226 6 Land Ownership in Delaware's Coastal Zone (1970) . . . . . . 227 7 Development of Delaware's Little Bays (1938-1969) . . . . . . 227 8 Grouping from the Literature of Selected Estuarine and Marine Fishes According to Physiological Studies and Studies on Their Resistance, Tolerance and Oxygen Consumption . . . . . . . 247 9 Cumulative Annual Growth of Summer Flounder by Sex . . . . . 400 ILLUSTRATIONS Figure I The Relationship Between Salinity and Plant Zonation in a Delaware Salt Marsh . . . . . . . . . . . . .. 7 2 Estuarine Food Chain .... . . . . . . . . . . . 19 3 Arrow-Arum . ................. 54 4 Arrowhead . ................. 55 5 Cattails . . . . 56 6 Big Cordgrass .............. 57 7 Salt Marsh Cordgrass .............. 58 8 Groundsel Bush ................. 59 9 High Tide Bush ................. .60 10 Marsh Mallow . ............... 61 11 Pickerelweed ................ 62 12 Pickerelweed . . . . . ............ 63 13 Reed Grass . . . . . . ............ 64 14 Rush . . . . . . . . ......... 65 15 Spike Grass. . . . . . ........... 66 16 Salt Hay . . . .......... 67 17 Threesquare. . . . . . . . ....... 68 18 Tide Marsh Water Hemp . .. . . . . . . . . . . . 69 19 Wild Rice . ..... . . 70 20 Zone I, Cordgrass Marsh .. .. . . 77 21 Zone II, Salt Meadow Marsh. . . . 79 22 Zone III, Salt Bush - Salt Meadow Marsh . ....... 81 23 Zone IV, Reed Grass Marsh . . . .......... 24 Zone V, Transition Marsh . . . 85 25 Zone VI, Arrow-Arum Marsh . . . 87 26 Generalized Wetland Atlas, Key Map . ......... 89 27-50 Generalized Wetland Atlas . . .......... 90 51 Wetland Drainage Areas of Delaware . ........ 117 vi. TABLE OF CONTENTS (continued) Figure Page 52 Illustration of Vegetative Zones Within a Drainage Area: #11, St. Jones River . . . . . . . . . . . . . ..120 53 Longitudinal Section of a Dredge Lagoon, Typical of the Development Around the Small Bays in Delaware . . . . . 169 54 Dredging . . . . . . . . . . . . . . . . . . . 174 55 Dredging .. .. . . .......174 56 Rip Rap and Bulkhead ....... . . . . . . . . 175 57 Bulkheading . . . . . o . . . . . . 175 58 Dredge Spoil Disposal 0.. . . . .. ...0179 59 Solid Waste Used as Fill . . .. . . . . ... 179 60 Dredge Fill and Bulkhead . . . . . . . ......180 61 Dredge SpollDisposal Pile. .. .. ..,. .. .. .18o 62 Impoundment .. . ... . . . . . . . . . . . . 192 63 Impoundment. .. . .. . . . . . . . . . . . . 192 64 Sluice Gate . . . . . . . . . . . . . . . . . . 193 65 Tide Gate . . . . . . . . . . . . . . . . . . 193 66 Ditching . . . . . . . . . . . . . . . . . . . 203 67 Ditching . . . . . . . . . . . . . . . . . . . 203 68 Solid Waste Disposal .... .... 210 69 Solid Waste Disposal and'Bulkhead ..... 210 70 Land Use Change: Masseys Landing Area - 1938 .. .. 218 71 Land Use Change: Masseys Landing Area - 1954 . . . . . . 219 72 Land Use Change: Masseys Landing Area - 1973 0 . . 220 73 Dredge Lagoon and Mobile Home Development . . . . . . . . 221 74 Marina . . . . . . . . . . . . . . . . . . . 231 75 Marina . . . . . . . . . . . . . . . . . . . 231 76 Suspended Sediment Concentration Map . . . . . . . . . 234 77 Environmental Dissolved Oxygen Concentration . . . . . . . 250 78 Relationship Between Estimated Natural and Acceptable Seasonal Minimal Oxygen Concentrations . . . . . . . . . . . . 250 79 Molecular Movement Explanation . . . . . . . . . . . 272 80 Salinity Distribution of Delaware's Tidal Wetlands . ...276 81 Tidal Flushing Map of Delaware . . . . . . . . . . . 282 82 Diagram of Typical Fish With Terms Used in Life Histories .. 286 83 Clearnose Skate . . . . . . . . . . . . . . . . 294 84 Little Skate . . . . . . . . . . . . . . . . . 295 * ~~~85 Atlantic Sturgeon . . . . . . . . . . . . . . . . 300 86 American Eel . . . . . . . . . . . . . . . . .307 * ~~~87 Alewife . . . . . . . . . . . . . . . . . . . 312 88 American Shad . . . . . . . . . . . . . . . . . 313 89 Blueback Herring . . . . . . . . . . . . . . . . 314 90 Atlantic Menhaden . . . . . . . . . . . . . . . . 319 91 Anchovy . . . . . . . . . . . . . . . . . . . 326 92 White Catfish . . . . . . . . . . . . . . . . . 331 93 Channel Catfish . . . . . . . . . . . . . . . . 332 94 Brown Bullhead . . . . . . . . . . . . . . . . . 333 95 Munmmichog . . . . . . . . . . . . . . . . . . 338 vii. TABLE OF CONTENTS (continued) Figure Page 96 Striped Killifish . . . . . . . . . . ..... 343 97 Atlantic Silverside . . . . . . . . . . . ... 349 98 White Perch . . . . . . . . . . . . . . . . . 353 99 Striped Bass . . . . . . . . . . . . ... 357 100 Winter Flounder . . . . . . . . . . . .... 362 101 Yellow Perch . . . . . . . . . . . . .... 369 102 Bluefish . . . . . . . . . . . . . . . . . . 375 103 Spot . . . . . . . . . . ........ 379 104 Croaker (Hardhead) . . . . . . . . . . .... 384 105 Weakfish (Sea Trout) . . . . . . . . . . . . . ... 390 106 Northern Puffer ............... 395 107 Summer Flounder . . . . . . . . . . . .... 401 108 Hogchoker . . . . . . . . . . . . . .... 406 109 Jellyfish ............. . 413 110 Quahog (Hard Clam) . . . . . . . . . . . 421 111 American Oyster . . . . . . . . . . .... 428 112 Oyster Drill . . . . . . . . . . . . .... 433 113 Blue Crab . . . . . . . . . . . . . . . . . 440 114 Copepod - Summer Distribution, Acartia tonsa . . . . . . . 444 115 Copepod - Winter Distribution, Acartia tonsa . . . . . . . 445 116 Copepod - Summer Distribution, Eurytemora (h & a) . . . . . 446 117 Copepod - Winter Distribution, Eurytemora (h & a) . . . . . 447 118 Copepod - Summer Distribution, Pseudodiaptomus coronatus . . . 448 119 Copepod - Winter Distribution, Pseudodiaptomus coronatus . . . 449 120 Copepod - Summer Distribution, Centropages (t & h) and Temora longicornis . . . . . . . . . . . . . . . 450 121 Copepod - Winter Distribution, Centropages (t & h) and Temora longicornis . . . . . . . . . . . . . . . 451 122 Copepod - Summer Distribution, Cyclops viridis . . . . . . 452 123 Copepod - Winter Distribution, Cyclops viridis . . . . . . 453 124 Amphipod - Summer Distribution, Gammarus fasciatus . . . . . 454 125 Amphipod - Winter Distribution, Gammarus fasciatus . . . . . 455 126 Oppossum Shrimp - Summer Distribution, Neomysis americana . . 456 127 Oppossum Shrimp - Winter Distribution, Neomysis americana . . 457 ACKNOWLEDGEMENTS Throughout the course of the Wetlands and Water Resources Atlas project, our group has relied on the thoroughness and excellence of scientists, past and present, who have worked in Delaware's wetlands and on her tidal waters. Certainly we cannot begin to thank all those from whom we have borrowed ideas, concepts and facts. However, we would like to acknowledge first, all those at the College of Marine Studies who helped us uncover and collect data -- a task which was vital to our overall effort. Secondly, thanks to our friends in the State Planning Office who worked with us constantly, tMssrs. Dave Hugq and Ben Coston. Mention should also be given to our two "watchdogs", Joel Goodman and Paul Jensen. We would also like to recognize Norman Wilder, Charlie Lesser, Betty Ann Allen and Jack Linehan for their input to our Survey of Delaware's Tidal Wetlands. And, last, but as usual, not least, we are greatly indebted to Ms. Ellen Ganzman for her typing skill, patience, and always smiling face. Larry Thornton Technical Director Delaware Wetlands and Water Resources Atlas Project ix. INTRODUCTION It has been nearly twenty years since Delaware has produced an authori- tative and comprehensive inventory and assessment of the State's wetlands and water resources*. Most of the changes since then, both good and bad, have resulted from the deliberate actions of man. This report, then, should be a valuable tool for those who have an interest in actions that in some way would affect the wetlands of the State. It should be remembered, though, that a study of the wetlands cannot stop right at the wetlands boundaries. There are numerous interchanges occurring which inextricably tie the wetlands to their surroundings. For instance: there are exchanges of water and air (and their contaminants); animals migrate; fish may spawn in one area and spend all or a part of their adult lives in another place; deer often browse in the marshes and sleep and seek shelter in the uplands; birds and fur-bearing mammals carry and drop seeds from other places; and so forth. These are but a few of literally hundreds of examples that we can find of these interchanges. It quickly becomes evident that wetlands are not only of great importance in their own right but that they are a part of a larger, complex system. For effective wetlands management, it is also necessary for one to under- stand the interrelationships that exist within and between the wetlands and the water resources of Delaware. This report provides the background data that is necessary for such an understanding. Delaware has a wetlands law that carefully defines the legal boundaries of the State's wetlands. This report complements that law by presenting the biological involvement of the wetlands. This is done by first presenting the *Delaware State Coordinating Committee, 1959, State of Delaware - Intrastate Water Resources Survey. X. principles of the processes which are at work in the wetlands. Then, the life histories of the shorebirds, fish and other marine life are described in the text, and where appropriate, by graphic presentations. In the report, wetlands are classified, in most cases, by the predominant type(s) of vegetation. In Delaware there are eight zones of wetlands. Their characteristics have been identified, and maps have been prepared showing the extent of the different zones. It is generally agreed that certain activities are harmful to wetlands. For instance, dredging adversely affects the benthic (occurring at the bottom of a body of water) organisms in a body of water, and this is often doubly destructive since additional environmental damage usually occurs wherever the dredged material is deposited, whether at the site or in deeper water. Most development activities in the wetlands have visible environmental impacts, with some, such as landfills, dredging, and spoil disposal being very destructive to living things. Other activities, such as impounding, draining and crop harvesting, may be harmful in some respects, but they may be beneficial in providing food or shelter for plants or animals that did not previously inhabit the area. There is a lot of truth in the statement that "an environment cannot be destroyed; it can only be altered". It is hoped, however, that this report will be used in weighing the consequences of a proposed activity so that conflicts between progress and the environmental integrity of our wetlands will be reduced to a minimum. Described in the report are the habits and occurrences of the wetlands wildlife. Also, the environmental parameters (the life-sustaining limits of several measurable things, such as oxygen, temperature, etc.) are given for many of the estuarine wildlife species. In addition, maps showing distribution xi. information about the adult and juvenile populations, spawning areas, and other data are included for the estuarine species. The environmental parameters and the maps, together, show that minute variations in one or more of the critical parameters can shift or eliminate a whole population. Companion maps show the flushing actions and the salinity levels of Delaware's tidal waters, both of which have significant effects on the types of plant and animal life which occur in the wetlands. In addition to the reference lists which are specifically noted in the Table of Contents, there are specialized reference lists following most sections of this report. In Delaware, as in many other places, wetlands continue to be lost as development irreversibly takes parcel after parcel of land from the inventory of natural wetlands. It is hoped that the information presented in this report will be used as a guide by the citizens of Delaware when weighing the conse- quences of proposed activities which would have an impact on our wetlands and water resources. This is Technical Report Number Two, prepared by the College of Marine Studies as part of the Delaware Coastal Management Program. The recom- mendations included are solely those of the authors and do not necessarily reflect the opinions or support of the Delaware State Planning Office or the Office of Coastal Zone Management of the U.S. Department of Commerce. xii. SECTION I WETLANDS SECTION I - WETLANDS GENERAL PRINCIPLES OF WETLANDS ECOSYSTEMS Looking out upon the marshes and wetlands of Delaware, it might appear that they are simple ecosystems. Only a few types of plants and animals live in such a habitat and of those that do, one or two species tend to dominate. In Delaware's salt marshes, cordgrass (S. alterniflora) dominates almost every marsh. Similarly, a few types of animals such as the fiddler crabs, marsh mussels and clapper rails dominate the marsh animal world. Researchers are discovering that the simplicity that we associate with the wetlands is far more a reflection of our lack of understanding of these dynamic ecosystems rather than a reflection of the true nature of tidal marshes. Wetlands organisms have to contend and interact with a combination of biological, physical, chemical, and geological processes to which organisms in other ecosystems are not normally exposed. The fact that few species are present in the marshes is indicative, then, of an extremely stressful ecosystem in which few animals and plants can successfully thrive. Similarly, the apparent stability seemingly evident among some mature wetlands ecosystems is not an indication that the processes of ecologic activity have ceased to occur or have been reduced in intensity. The stable wetland ecosystems, like a mature forest, are comprised of many complex processes that have successfully adjusted to one another but which do not necessarily change the outward appearance of the forest or marsh itself. The history of marshes and wetlands is one in which these numerous and complex processes are continually changing and interacting with one another. Marshes and wetlands, although they appear to be static, are truly complex and dynamic systems. In considering the principles underlying wetlands ecosystems, it becomes difficult to identify and discuss individual processes one from another. They are all interdependent, each affecting the expression of the others in important, sometimes subtle ways. It is the biotic or biological component -- the most obvious to the casual observer -- which is usually considered the culmination of the other processes responsible for marsh and wetland development. However, it is the non-biotic factors; the chemical, physical and geologic processes, which make the rules and mold the environment with which the biotic community must contend. Non-biotic processes active in wetlands ecosystems can be grouped into two general categories, those that act continuously and occur on a somewhat regular basis, and those that are noncontinuous which occur more sporadically and which might be considered abnormal or extreme events. In the first category would be included such parameters as the tides, stream flow, light, temperature, and sedimentation cycles, and in the second such occurrences as storms, fires, and man-induced disturbances. It is not always easy to determine which group of factors has the greatest effect on the development of the system. At first, it might seem that the continuously acting factors would dominate since they affect the system directly at all times. However, one major storm, one man-made ditch or one large pollution point source can easily influence the wetland system for long periods of time. The effects of extreme events are not easily quantified or well understood but it must be kept in mind that they are important. It is generally agreed that tidal inundation, drainage, and, to a large extent, salinity are the most important non-biotic factors which determine plant and animal distribution in the wetlands. Delaware has a variety of saltwater systems that are affected by tides and influenced by salinity. The large Delaware Bay, an estuary, is the most obvious, but we also have barrier bays (Indian River, Rehoboth and Assawoman Bays), small estuaries at the mouth of our tidal rivers (Mispillion, St. Jones, etc.) and the tidal creeks and guts located farther inland. The specifics of the tidal inundation in each of these systems 2 is different from the others. The tides have several components which determine the kinds of effects that they have on a wetland system -- their intensity, vertical inundation, range and rhythm. The intensity of the tides refers to the amount of water and the force with which the water flows through the system and it determines the magnitude of the mechanical disturbance to the area. The vertical range is an indication of the height the water reaches an high tides, and so, determines how far the chemical effects of the saltwater will be carried up the banks of a tidal stream. The rhythm of tides refers to the natural frequencies of the tides. The tides operate on a lunar rhythm which is out of phase with the diurnal rhythm of day and night; therefore, as the high and low tides progress through the lunar month (28 days) they occur at different times of the day and reach different heights each day. In Delaware, there are generally two high tides and two low tides in a day with the high and low tides occurring approximately one hour later from day to day. The dominant factors affecting the height and frequency of tides are the gravitational forces of the moon and the sun, but other factors are involved. Due to the varying gravitational effects of the moon and sun, there occur each lunar month two spring tides and two neap tides. A spring tide is characterized by higher than normal high tides and lower than normal low tides which results in a large tidal range. A neap tide has lower than normal extremes in tide height which result in a small tidal range. Spring tides occur near the times of new and full moons; neap tides occur midway between spring tides. The actual level reached by any high or low tide depends on local factors of topography, stream flow, wind speed and direction in addition to the astronomical influences of the moon and sun. 3 In a tidal cycle, for instance, one marsh (or one area of a particular marsh) might be inundated at high tide for a different period of time than another marsh (or another area of the same marsh). Such emergence-submergence patterns, as they are called, determine how long particular areas are in direct contact with saltwater, and hence how great the influence of saltwater is on the plants and organisms covered. Although the height and time of the tides is predictable,, the prediction is never exact. The distribution and penetration of the salt contained in seawater into the wetland system is probably the most important parameter controlled by the tides. The salt concentrations of the soils, sediments and water are dominant factors determining the structure and zonation of the biological commiunities of marshes and wetlands. High salt concentrations dictate that only organisms having specialized and efficient means of eliminating large amounts of toxic salts, or those which have developed some kinds of immunities to these toxic effects, will be able to survive in saltwater inundated areas. The number of plants and animals that can withstand the saline conditions of the salt and brackish water marshes is indeed small. While the simple presence or absence of salt is in itself important, the nature of the fluctuations occurring in the salt concentrations in particular marsh areas is equally important. Flooding tides in near shore environments are characterized by high salinity water due to the relative amounts of salt and freshwater in the system during these different tidal cycle stages. (See Map of Salinity Distribution of Delaware.) Most areas in the marshes then are exposed to waters of varying salinities periodically throughout the day. Depending on how far up or downstream a particular area is or how far away from the stream channel an area is, the degree of saline fluctuations can vary greatly. It is much more difficult for organisms to adapt to very greatly 4 fluctuating salinity conditions than it is for them to adapt to a less fluctuating though possibly higher salt environment. Species that can withstand a mean salinity level of 17%o in an area with a salinity range of 16-18%0 might not be able to withstand a mean salinity level of 17%o in an area where the range is 5-25%0. In addition to the salinity regime of the waters, there are also important salinity regimes of the soils and sediments. Since the salts tend to be retained, translocated and often concentrated in the soils, the soils have important effects on the distribution of salt in any system. Areas which are only infrequently inundated with saltwater can have soils or sediments with very high salt concentrations, for as the tidal water percolates through the soil and/or evaporates, the salts remain in the soil. Every time the area is washed with saltwater, more salt is added to the soil. The salt concentration does not increase indefinitely for only so much salt will be retained in the soil depending on the soil type, frequency of innundation, precipitation cycles and groundwater levels. But soil salinities must be included in those impor- tant parameters controlling the structure of the biological commnunities of marshes and wetlands. In salt pannes, located in areas above mean high water, the salinity of the soil can exceed 100%o (see Figure 1). The alternating cycle of inundating and receding waters affects much more than just the distributions of salt. The temperature of soils, sediments and water, the amount of light reaching the marsh surfaces, the patterns of nutrient cycling in both soils and waters, the transport of sediments, the existence of the groundwater system, the exchange of gases between organisms and their environments, the physical development of the marsh surface and all activity cycles of the marsh organisms are some of the many factors strongly influenced by the tidal cycle. 5 As the distance from the mouth of a creek or river increases, the effects of tidal inundation are reduced accordingly. Such changes in tidal influence can be seen in changes that occur in the nature of the marsh community as one proceeds both laterally across the marsh surfaces away from the stream channels and up the course of the stream system. Lateral zonation of the vegetation is very characteristic of most of the marsh and wetland areas of Delaware! Cordgrass (Spartina alterniflora, Zone I), the major grass species of Delaware's wetlands, exists in those areas most affected by tidal inundation. Along the creek banks where inundation is most frequent and water fluctuations the greatest, cordgrass is found to grow in mostly pure stands of very tall plants. The only other vegetation in this zone are the minute algal forms that grow throughout the marsh systems. As the degree of tidal inundation decreases so does the height of the Spartina community so that areas of medium sized and short plants are found behind the tall Spartina zones. Usually, these zones are pure Spartina except at their landward edges where other plants begin to appear (see Figure 1). Salt hay (Spartina patens) and spike grass (Distichlis spicata, Zone II) are two of the common species found in areas bordering the cordgrass zone (Zone I). These species occur together as well as in almost pure stands of each depending on the characteristics of the marsh, The locations in which they are found are, topographically, slightly higher than the cordgrass areas which is the reason the salt hay-spike grass zones are not normally inundated by the tides. These plants can withstand high soil salinities but not the periodic inundations that the cordgrass can tolerate. More species such as high tide bush (Iva frustescens, Zone III) and groundsel bush (Baccharis halimifolia, Zone III) are found landward of the salt hay and spike grass where tidal influence is reduced (see Figure 1). *See detailed discussions of Wetlands Zones. 6 FIGURE I THE RELATIONSHIP BETWEEN SALINITY AND PLANT ZONATION IN A DELAWARE SALT MARSH SALT PANNE SPRING HIGH TIDE 125 MEAN HIGH WATER-Of DITCH"~ 100 MEAN LOW WATER5 MAXIMUM MAXIMUM IDAL CREEK MARSH PEAT SALINITY 50 (%o ) '-MAXIMUM SURFACE SOIL SALINITY \ 25 0 CORDGRASS 'fSALT HAY ZONE I ZONE 11 ZONE IIIa IV UPLANDS SALT BUSH CORDGRASS SALT HAY HIGH MARSH I REEDGRASS Some areas such as tidal creek banks are also present in which obvious vegetation is lacking. Because of the mechanical disturbances commion to the creek and ditch banks in the marshes caused by water flow and activity of some crab species, grasses are often unable to successfully colonize these areas. Some of the minute, microscopic algal forms are, however, present on the exposed mud surfaces in usually very characteristic assemblages. There are also sites an the marsh surface, known as salt pannes, where the grasses are not present. Some factors, not completely understood, have created these usually small, bare areas. The chemical nature of the soils in the salt pannes is usually different from that of the surrounding marsh soils, probably accounting for the absence of the grass. Again, these salt pannes are colonized by some smaller algal forms for which the conditions of the panne are not too severe. In concert with the floral changes one sees when traversing the marsh, are changes in the types of animals found in the particular floral zones. The crabs and snails common to the tall cordgrass (S. alterniflora, Zone I) marsh, for example, are different from those common to the salt hay marsh (D. spicata and S. patens, Zone II). Faunal zonation has not been as intensively mapped as the vegetative zonation. However, scientists unfamiliar with all the details of the faunal distributions do know that species, zones or territories do exist. Interestingly, the relative dominance by a few species of plants in the marsh is mimicked in the faunal kingdom as well, for only a few species of animals are present in large numbers over extensive areas of the marsh surface. Other species are represented by even fewer individuals with a more limited spatial distribution. The floral zones have distinct growth forms that offer certain advantages to particular types of animals. These vegetational characteristics are augmented by characteristics of the tidal regime in different areas and partially control the distribution of animals. The relationship between animals and vegetation is a complex one. The obvious benefits accrued by the animals from vegetation are protection and shelter as well as general habitat sites and food sources. The benefits to the vegetation are more obscure. The influence of tidal saltwater is reduced in the upstream portions of the wetlands as sources of freshwater become more prominent. While freshwater performs many of the same functions as does the saltwater (affecting nutrient cycle, temperature cycles, detrital transport, sedimentation and erosion cycle, among others), fluctuations in the character of freshwater are of a much lower magnitude than are those of estuarine waters. The chemical composition of fresh- water is relatively more stable and exhibits less of a physiological stress than waters of the intertidal areas (see Salinity and Estuarine Organisms). Some fluctuations do occur on a seasonal basis,but these are still of a lower magnitude than those fluctuations occurring daily in the strongly tidal influenced areas. As a result of the more constant conditions and lower salinity levels, greater numbers of species are found in the upper wetlands areas (transition marsh, Zone V). As one progresses upstream through the marshes, the increased species diversity (both plant and animal) is usually very evident and well- coordinated with the decreasing salinities and degree of stressful environmental fluctuations. Although it is relatively more difficult for most organisms to survive in the intertidal wetlands areas, those that do can receive some benefits from living in such a habitat. The major benefit is that competition from other species for the same resources is reduced, as are some predator pressures. In the low marsh areas, for example, cordgrass (S. alterniflora) finds few competitors and exists in almost pure stands over large areas bordering the bay 9 and tidal creeks. In areas of fresher water where cordgrass is still present, it must share the area and its resources with numerous other plants like the rushes (Scirpus sp.), marsh mallow (Hibiscus palustris), bit cordgrass (Spartina cynosuroides) and reedgrass (Phragmites communis) that can effectively compete with cordgrass in these freshwater areas. The distinctions between high and low marsh and up- and down-stream portions of a wetland area are obviously somewhat artificial. They are as much the creations of scientists who must dissect the systems in order to understand them as they are real and distinct components of the marshes and wetlands. Such distinctions become much more artificial when considering the flow of energy through these systems. All the organisms, processes and areas are very directly connected in this regard -- without the divisions. As discussed in more detail in a following section, the productivity of the wetlands begins with the energy captured by it in various vegetative communities. Through several pathways, this energy Is then channeled to other levels in the system and is eventually con- sumed by the numbers of fish and other animals of the estuaries. It is an intricate energy-flow system that reflects both the complex and dynamic nature of the wetlands ecosystems. WETLANDS AND ESTUARINE PRODUCTIVITY Except for a handful of farsighted individuals who were perceptive enough to consider the importance of the wetlands, people have historically viewed these areas more as wastelands than as anything else. Unlike the ties between man and the forests, farmlands, and cities which have always been strong and fairly obvious, those between man and marsh systems have been weaker and more obscure. As a result, people have looked upon wetlands as useless and non- productive. The main Importance of the marsh systems, then, usually depended on 10 how they could be modified to resemble the systems more useful to man. It is now known that the true importance of marshes and wetlands lies not in their modification potential but in their basic function as the foundations of total estuarine productivity. Our estuaries, those areas where salt and freshwaters meet, including the marshes, tidal creeks, tidal mud flats and bays, are decidely some of the most productive systems known. Man has created certain specialized agricultural systems that are extremely productive and rival the estuaries in this respect. But, he has done so only at the expense of great amounts of energy subsidies in the forms of manpower, fertilizers, pesticides and machinery. The estuarine areas, however, exhibit high productivity without the direction or input of man; they are self-fertilizing, self-sustaining energy production and transfer systems. Each estuarine system is slightly different from all others for the conditions responsible for their development and maintenance -- the geology, the geographic location and climatic regime, the circulation and tidal patterns, and the chemical characteristics of the water -- vary greatly from estuary to estuary. Such variations are reflected in both the physical structure of the system and the assemblage of plants and animals that are characteristic of it. What all these systems do have in common is that a large part of the productivity of the estuary is dependent on the organic material produced in the marsh and wetland areas. Green plants are the only organisms which can capture the energy of the sun and transform it into organic material. Wetlands with their various vegetative communities are the primary sources of organic material for estuaries. Primary producers of the wetlands can be divided into three groups: the emergent grasses, the phytoplankton of the water, and the attached or edaphic algae of the mud surfaces. Each one of these groups is present to some extent in all marsh systems. Just how much each contributes depends upon the particular characteristics of each marsh and estuary. In most cases, in fact, the contri- butions are yet to be adequately defined for scientists have not identified all of the factors controlling productivity. In Delaware's marshes,as in most marsh systems, it appears that the importance of the emergent grasses is far greater than either the phytoplankton or edaphic algae. The phytoplankton and edaphic algae are important for scientists are discovering that their contribu- tion to primary productivity, although small, is an essential component of a healthy estuary. Edaphic Algae The edaphic algae are plants both microscopic and macroscopic which grow on the exposed mud surfaces of the marsh. They are found in numerous places in the marshes and wetlands including the open areas between individual grass stems in zones colonized by the grasses, on the banks of the tidal creeks, and on the open surfaces of the mud flats. While some of these areas can be some distance from the regular flow of the waters of the marsh, most are at least within the range of the high spring tides. Therefore, there is a direct link between these edaphic communities and other systems in the wetlands. Most of the time, these mud algae seem very inconspicuous, especially when compared to some of the emergent grasses. In truth, the quantity of algae that can be found at any one time (the standing crop) is very small. The standing crop, however, is not really indicative of how much material these plants produce or how much energy they can provide for other groups. Each time a particular area is washed by the tides, some of the algae is removed with the receding waters. In the water they are available to the creatures that eat 12 the algae -- the zooplankton, small fish and benthic invertebrates, or to the bacteria that break them down if they are not directly consumed. The algae that are left on the marsh surfaces are constantly growing and reproducing so that those algae that were removed with the water are quickly replaced. This pattern of growth, loss, and rapid replacement goes on continuously. Edaphic algae are also important for the generation of oxygen during the photosynthetic process. The lack of detailed information concerning edaphic algae productivity does not obscure the fact that these forms are important primary producers of the estuaries. This importance is further heightened by the knowledge that the edaphic algae appear to be very active in the fall and winter when the grass communities are lying dormant. During these times, the food they provide for the plant and detritus eating organisms of the estuary can be especially important. Phytopl ankton Phytoplankton are minute plants that are found living in all natural water systems. Freshwater lakes, bogs, ponds, streams, and rivers plus tidal creeks, ponds, bays and even the upper portions of the oceans all have their own complement of phytoplankton. The forms found are very diverse but they all share the characteristic of being able to produce organic matter from sunlight, water and CO2. The pigment systems of the phytoplankton are slightly different than those of larger plants for the sunlight used by them is that which passes through both air and water. The light available to them, then, has slightly different characteristics than that available to emergent vegetation, and the phytoplankton have adapted pigment systems to make the best use of this light. Like the edaphic algae, the phytoplankton standing crop is usually 13 relatively small compared to the amount of material this community produces. Nutrients in the water are utilized by the phytoplankton for their growth, maintenance and reproduction. The phytoplankton in turn, are a food source for a host of herbivores including zooplankton such as the copepods, bivalves (such as clams and oysters) and larval fish. The crop of phytoplankton is usually kept low because increases in the numbers of phytoplankton organisms are followed quickly by increases in the number of herbivores. As in the edaphic algae, the relationships between the phytoplankton and its predators, the grazing herbivores, the decomposing bacteria, and the nutrient supply in the water, are very complex. Phytoplankton are probably more important in the open areas of the estuary such as the bays than they are in the small tidal creeks of the true wetlands areas. But they are very productive and their productivity ultimately depends on the nutrients contributed by the wetlands areas to the entire estuary. It is difficult to set figures on how much material the phytoplankton produce; how much of this group is consumed; how much is decomposed; what amount of nutrients is involved; and finally, how much of this production ends up as a higher organism. The role of the phytoplankton as a primary producer, however, is of extreme importance to the estuary and total wetlands. The Emergent Grasses By far the most important group of primary producers are the grasses, which dominate the marsh landscape. While many different plants might be found in various wetlands areas throughout the state, most of the production can be traced to a few dominant species. The salt marsh cordgrass, Spartina alterniflora, is definitely the most prevalent and most important grass in Delaware's wetlands as it is in the wetlands along the entire Eastern seaboard. 14 Cordqrass productivity is supplemented by that of salt hay, Spartina patens, spike grass, Distichlis spicata, several species of the Juncus group, some of the rushes (Scirpus sp.) and others. Unlike the small amount of algae present at any one time, there is a very large standing crop of cordgrass present at most times during the growing season. These grasses are very productive despite the low efficiency at which they convert sunlight, water and C02 into plant material. The most productive Atlantic coast marshes are estimated to capture only I per cent of all the incident sunlight and many marshes capture less than 0.5 per cent. Further, of the energy these plants receive from this light, most of it is used for the maintenance of the plants themselves. That is the price that halophytes (plants which grow. in salty habitats) pay for living in this harsh estuarine environment. These inefficiencies, however, are compensated for by the amounts of grasses involved, the long growing season, the habits halophytes have developed and the large amounts of nutrients and water available to wetlands plants. There is always enough plant material produced so that large amounts of plant material, detritus and consequently nutrients, are exported to other parts of the estuary. The nutrient reserve that marsh plants enjoy takes a long time to develop and is an integral part of the development of the whole marsh area. Marshes are created through a complex process involving water flow characteristics, sedimentation rates and sediment types, and invasions by the various plants and animals which modify and contribute to this developmental process. As the marsh grows, much of the organic material produced by the plants and animals becomes mixed with sands and muds creating the marsh soils. In the early phase of development the amounts of organic material being incorporated into the soil system are larger than those being extracted so a reserve of organic material builds up. This reserve is further augmented by the nutrients being carried 15 in the waters that flow through the marshes. Much of the waterborne nutrients become incorporated into the soils as the water percolates through them. In time a fairly large nutrient reserve is built up in the soil system of these areas which, combined with the nutrients constantly being supplied by the flowing waters, forms the basis for the productivity of the grasses. The productivity of the Spartina is not important in itself since it is not directly useful to higher organisms. The organic material of the grasses must be conv erted to other forms before the cycle is completed. The conversion only takes place through two pathways in estuarine areas: direct utilization of live material and utilization of the dead plant material, the latter appearing to be the more important pathway. VIery little of the live marsh grasses are directly consumed unlike an agricultural crop whose energy is utilized directly by the consumption of live material. Investigators estimate that as little as 5 to 8 percent of the total material produced by the Spartina community is directly consumed by organisms, usually insects and marsh crabs. This percentage varies, but it is obvious that only a relatively small amount of the grass is ever utilized while still alive. Plant decomposition through the detrital cycle is the process through which Spartina makes its great contribution to the estuary. As the plants die and fall to the ground, they are physically broken down by the action of the water and some of the animals of the marsh. As this mechanical breakdown proceeds, chemical breakdown of the material is also occurring. This is accomplished by the actions of the numerous bacteria and fungi of the marsh surfaces and waters as well as many macroinvertebrates that find the plant particles very suitable nutrient sources. The microorganisms rapidly colonize the detritus, extracting what they can from the plant tissues. As the bacteria and fungi grow and colonize the material, not only do 16 they break down the plant detritus into more elemental components, they also create important food particles for other organisms. In itself, plant detritus is not especially nutritious. Live Spartina, in fact, is only about 10 per cent protein; and, by the time the plants die and fall to the marsh surfaces, the protein content is very much less than this. By comparison, the protein con- tents of bacteria and fungi are high and as these microorganisms multiply on the plant particles, they multiply the overall nutritional value. The filter- feeding organisms that ingest such particles -- notably the zooplankton animals -- then find detrital particles a very nutritious package. Some of the primary consumers utilize the whole microorganism/plant particle; others just strip off the bacterial colony and return the detrital particles to the water where they are recolonized by more microorganisms. This process continues over and over again until the plant material is finally broken down. Also in this process, some of the components of the plant material are simply released into the water and serve as nutrient sources for the phytoplankton and benthic algae. Overall, the detrital cycle is an effective energy cycling system. Detrital material has storage, transport and buffer functions that allow for more complete utilization of energy. Until the plant material is broken down, it represents stored energy and as such can be used as an energy source for some time. Likewise, through the actions of the water in the marshes and estuaries, this stored energy can be transported from one area to another. Closely associated with these two functions is the buffer function wherein detritus provides energy to the system when other energy-producing components are nonfunctional. This characteristic becomes important in the fall, winter and early spring and assures that a year-long nutrient source is available to higher levels of the estuarine ecosystem. 17 Most of the zooplankton organisms are dependent both on the phytoplankton of the estuaries and on these bacterial-detrital particles for their energy sources, as are other larger invertebrate filter feeders. Herbivores are then preyed upon by many types of animals including other zooplankton, and young and adult fishes of all types. The specific paths the energy is cycled through are extremely complex but all start originally with the phytoplankton. Figure 2 is an example of a "typical" estuarine food chain which illustrates the dependency of the estuarine animals on the sun energv fixed by plants through photosynthesis. Both types of food chain, the detrital food chain and the direct utilization chain, are included in the figure since the two chains are not independent. The organisms shown are meant only to be representative of the many found on each trophic level. The trophic level classification is one of function, not of the species as such; a given species may occupy more than one level depending on the source of energy consumed. Of the available sun energy only 0.5 to 1.0 per cent is fixed by the marsh plants; further, only 10 to 20 per cent of the food energy is passed from one trophic level to the next, the remainder being lost as heat. As a consequence, for every pound of bluefish or strined bass consumed by man, at least 150 pounds of plant material is required. While the wetlands make up only a small portion of the total land area in any region, it is estimated that 80 to 90 per cent of our total seafood harvest is dependent in one way or another on the estuaries. Most of the species of fish with which we are familiar spend important parts of their life cycle in the estuaries, either as spawning adults or as juveniles. The high level of wetland and estuarine primary productivity supports the zooplankton and other small invertebrates that the fish feed on. We have only to look at areas where wet- lands losses have been directly related to losses in important fish species to see that the connection is real. The wetlands areas are truly the foundation of estuarine productivity. 18 Figure 2 ESTUARINE FOOD CHAIN HUMANS TERTIARY CONSUMER BLUEFISH STRIPED BAS Trophic Level(Pmoms___ (carnivores) ~-. (Cynoscion) SKATES HERRINGS FLOUNDERS menhciden'1 SECONDARY CONSUMER Si LERSI DES Prlichthyl alewife Trophic LevelFOAEIS (Menidia)* SHIP ~dooleuronectes) (-_ornivores-eat animals) (FORAGE FSH ~-AMPHIPODS (Gammarus) k ~ ZOPLANKTOIN"N, PRIMARY CONSUMER p~cetsA 4'---,MOLLUJSCS Trophic Level CRAB= Seam)SODS- M ercen aria (herbivores-eat plants) /Cassra DETRITUS__ ------- PRODUCER Trophic Level DIATOMS, EDAPHIC ALGAE PLANTS PHYTOPLANKTON (green plants) t COROGRASS SALT HAY SALT BUSH (S. alterniflora) (D. sPicata ( Iva N (S atensi ( accas ANIMALS AND W4ETLANDS It is only in relatively recent years that man has begun to comprehend the role of the wetlands in the estuarine ecosystem. In particular, wetlands are said to be of utmost importance to the health and welfare of numerous fishes and shellfishes. Although this relationship is an extremely important and essential one, it must be kept in mind that the wetlands and marshes are also important to many other animals including song birds, ducks and geese, wadinq shore birds, birds of prey, fur-bearing mammals, plus some amphibians and reptiles. The dependence of these animals on wetlands must also be considered when establishing policies and programs for our natural systems. Much of the importance of wetlands to these other animals has become apparent only after the implementation of many mosquito control projects undertaken in the 1930's. Historically, there has been a definite conflict of interest between insect and wildlife management practices (see Ditching and Impounding). The ditching and draining of many marsh and wetland areas -- the most common manner through which mosquito control problems have been approached - has affected much more than just the mosquito populations. Usually, these manipulations have also resulted in major changes in the animal populations. Invertebrates, fur-bearing mammals, and many birds do not find the ditched marshes to be suitable habitats and so their use of these areas often declines although there is some conflicting data surrounding this point. It is in response to man's various activities and the presumed harm to associated wetlands organisms that the importance of properly maintained wetlands to the many types of animals whose livelihood depends on wetlands has become apparent. The list of animals that are commonly found and whose lives depend on the wetlands of Delaware is, indeed, a long one. Each of these animals plays an 20 important role in maintaining the ecological balance of the system as they interact with the wetlands by feeding, nesting, spawning and dying. Many of these animals spend their lives in particular zones or areas in the marsh. Yet, in many cases, it is difficult to determine specific ranges of certain wetl ands-dependent organisms. Every marsh and wetlands area is composed of different floral zones with each zone being characterized by particular vegetation types (see "General Principles of Wetlands Ecosystems"). Each vegetation type is a reflection of particular salinity, soil moisture and time of inundation existing in the different marsh areas which change across the marsh as the tidal and freshwater influences change. The plant zonation is the most obvious configuration existing in the biotic commiunity. But, the animals also reflect the changing pattern of marsh conditions to some extent in their own distributions. They inhabit those vegetative zones in which they are best able to produce the materials they need for their survival, and a relationship develops between animals and vegetative zones -- one that is dependent ultimately on the relationship between the vegetation and the tides. However, it must be remembered that the animal distributions are not always as distinct as are the plant distributions. The correlation between plant and animal distributions is a definite one, but it is not always an exact one. Animals are mobile organisms, and while some seem to move only in relatively small areas, others range over larger regions of the marsh from the upland margins to the tidal creeks. However, even these animals have a home base to which they return when their hunting is done and so they can be thought of in terms of a particular home zone. Of the animals that do spend most of their lives in one part of the marsh, 21 many are smaller forms such as the invertebrates, birds and small mammals. Invertebrates such as the snails (Melampus bidentatus), the fiddler crabs (Uca sp.) and the ribbed mussels (Modiolus demissus) are common low marsh inhabitants of Delaware's tide lands, The ribbed mussels have very little choice for they are attached forms, similar in this respect to the plants. They survive because they possess their own shelters (their shells) and filter food out of the tidal waters that continually wash over them. The crabs and snails, on the other hand, are mobile forms that still tend to stay in a relatively small area, bound to the environ- mental cycles existing there. Snails move up and down the grass stems with the rising and falling tides, while the crabs move in and out of the burrows they have dug in the mud. For food, both utilize the plant detritus that is always available on the marsh surfaces. For example, researchers in Delaware have found that the marsh crab (Sesarma) feeds directly on living cordgrass. Some marsh birds can be found in these low marsh areas where they remain for a large part of their lives. Clapper rails (Rallus lonqirostris) are typical low marsh residents who build their nests and raise their young amonq the stems of the tidal grasses. Both clapper rails and black ducks consume low marsh inhabitants, the crabs and snails. Seaside sparrows, red wing blackbirds and sharp-tailed sparrows consume principally cordgrass seeds. Some cordgrass is also consumed by insects which form the base of the diet of many birds. Another common inhabitant is the willet (Cataptrophorous semipalmatus) whose noisy call usually precedes any strange visitor. Among the small mammals who tend to remain in a fairly limited area are the meadow mouse (Microtus pennsylvanicus) and the muskrat (Ondatra zibethica). The meadow mouse is usually found in the landward edges of the wetlands near 22 the salt hay (Spartina patens) zone. Mice range over large areas but still spend much time in the area of their nests. The nests represent safety and shelter and during adverse conditions the mice seldom leave them. The muskrat is a very well known marsh inhabitant about which more will be said later. It, too, chooses a particular area in which to reside and tends to remain close by. There are also animals that are essentially upland species but that occassionally roam into the marsh and wetlands areas in search of food. Racoons (Procyon lotor), oppossums (Didelphus marsupiala) and woodchucks (Marmota monax) often travel into the lower marsh areas to feed on shellfish and crabs. When the conditions on the marsh are not too severe, as during neap tide periods, these animals may remain on the marshes for several days at a time feasting on these delicacies. Weasels (Mustela frenata), red and gray foxes (Vulpes fulva and Urocyon cineraoargenteus), deer (Odocoileus virginiana) and rabbits (Sylvilagus floridanus) also travel from upland to lower marsh areas on occasion. Most of the time the presence of these animals is known to us only through the characteristic tracks they leave on the marsh surfaces. Other extremely important users of the marshes and wetlands are the transient species to whom the marshes represent feeding and resting sites. The most common of these are the waterfowl that make great use of wetland areas during their migrations. Delaware is situated along one of the major flyways of the North American continent, and as a result, Delaware wetlands are used extensively by many different migrating species. Mallards (Anas platyrhynchos), pintails (A. acuta), blue and green-winged teals (A. carolinensis and A. discors), black ducks (A. rubripes), and gadwalls (A. strepera) are some of the duck species that can be found in Delaware's wetlands along with the magnificent Canada goose (Branta canadensis), the mainstay of the waterfowl hunter. The same necessities 23 that attract the more permanent marsh residents -- food, water and shelter -- also attract these migrating birds. The importance of the wetlands to the survival of the waterfowl species has been well established. The larger animals of the marshes distribute themselves partially according to their uses of the plant materials and partially according to their uses of the smaller invertebrates associated with each zone. Clapper rails are common in the tall cordgrass (Spartina) areas both because they use the cordgrass for their chief food sources, and fiddler and marsh crabs also live in the Spartina zones. Salt bush zones {Iva frutescens and Baccharis hamilifolia) offer nesting areas and shelter for a wide variety of wildlife but are of little nutritive value. Giant reed grass zones (Phragmites communis) are similar in function. In more brackish water sections where rushes (Scirpus sp.) and big cordgrass (Spartina cynosuroides) are common, periwinkles and marsh snails are also common and black ducks and teals can often be found here supplementing their plant diets with these invertebrates. Blue herons (Ardea herodins) commonly stalk the fishes which live in the intertidal waters. Predator-prey interactions also involve the top predatory species such as the foxes, the otter (Lutra canadensis) and the hawks. Foxes are sometimes seen in the upland margins stalking feeding ducks. Marsh hawks (Circus cyaneus), the most common bird of prey found in Delaware's wetlands, are often seen fringing many wetlands areas in search of the mice, rats and young muskrats upon which they feed. Most of the animal species that serve as prey for the predators are herbivores who derive their food from vegetation. The meadow mice exist partially on the seeds and young shoots of salt hay (Spartina patens) and spike grass (Distichlis spicata}. Seaside sparrows (Ammospiza maritima) are known to eat cordgrass (Spartina alterniflora) seeds. Canvasbacks, mallard 24 and pintall ducks often consume the seeds of the wild rice plants (Zizania aquatica). Even the large Canada goose, whose major predator is man, is a plant eater, feeding on widgeon grass (Ruppia maritima), cordgrass (S. alterniflora) and three-square bullrush (Scirpus americanus). The use of the plants changes as the seasons advance and as the physical structures of the plants change. In the spring, young tender shoots of marsh grasses and root stocks filled with starches are important food items. In the late spring and summer, the leaves and flowers are consumed because they are plentiful. In the fall and winter, fruits and seeds develop and attract many animals searching for food, while stalks of plants are sought after for nesting material. One of the most studied and important relationships of animals and wetlands is that of the muskrat, Ondatra zibethica, and several of the marsh grasses. Muskrats have always held an important place in the lives of people living near wetlands for they have provided both food and fur pelts. The market for both of these products has declined drastically in recent years, and this fact coupled with destruction of the muskrat habitat has lead to a reduction in the importance of the muskrat to man. But trapping continues in Delaware, and muskrats are still important components of the marshes they inhabit. Muskrats are more common in brackish water areas than in the saline areas for the foods they commonly utilize, Olney's three-square (Scirpus olneyi) and cattails (Typha sp.), grow in brackish water areas. Cordgrass (Spartina alterniflora) is usually present in these areas and is used by the muskrats as construction material for their houses and occassionally as food. Areas where all of these grass species are present support the best muskrat populations, but populations can also be found in less preferable areas. In these less suitable areas, the density and general health of the muskrat populations are known to be 25 lower than those characteristic of populations in the preferred habitats. Much of the relationship of the wetlands to the muskrat was brought to light after their habitats had been destroyed or considerably altered. Ditching has been noted to decrease the availability of freshwater in some systems leading to vegetational changes in the wetlands. Muskrat foods such as the rushes and cattails are often replaced by other less favorable food species, and this replacement leads to reduction in the size of the muskrat population that can be supported. Ditching also tends to create uplands by draining the marsh and lowering the water table. Hence, upland species of little value to the muskrat begin to invade areas that were once cordgrass, cattail, and bullrush. Similar post-ditching reductions have been noted in the invertebrate populations of the marshes and in the animal species which utilize these invertebrates as food. Some extensive studies have been made in Kent County marshes before and after ditching operations were completed in the later 1930's. The results of these studies showed that in most vegetative zones, the numbers of invertebrates found were significantly lower after the ditching operations had been completed. Reductions varied depending on the particular area and season but were usually around 50 per cent and often as high as 90 per cent of the pre-ditching populations. Therefore, even the predators whose food sources are not plants but the smaller marsh invertebrates are affected when the wetlands are disturbed. A more recent study has indicated that certain invertebrates, such as fiddler crabs and salt marsh snails, were more numerous in ditched marsh than in unditched marsh. Snails and crabs are typical of salt marsh bank-water interfaces. Consequently, it seems reasonable that increasing the area of marsh bank through the construction of ditches would also tend to increase the 26 abundance of these certain, specialized invertebrates. However, the great majority of salt marsh invertebrates do not inhabit this niche. Ditching, then, by lowering the water table of the marsh, tends to be detrimental to the majority of the invertebrates on the marsh. Not all actions of man have been necessarily harmful to the wildlife resources. Delaware enjoys a large winter waterfowl population because of the effort that has been devoted to creating attractive feeding sites for geese and ducks. Impoundments have been developed near feeding areas so waterfowl find proper food and shelter during their migrations. The impoundments have also been shown to increase the use of certain areas by other birds and mammnals. Where ditching lowers water levels, impounding increases freshwater levels leading to increases in brackish and freshwater plant species used as food by many animals. There are problems with impounding though, for this practice often appears to conflict with those attempting to maintain and improve fish and shellfish populations in the estuaries. Impounding prevents water from flowing out of the wetlands areas to the estuaries, and the estuaries are deprived of the nutrient materials these waters contain. The productivity of estuaries is directly dependent on the nutrient materials originating in the wetlands (see Wetlands and Estuarine Productivity). Without them, phytoplankton and zooplankton populations -- direct utilizers of wetlands nutrients -- might be affected. If these populations are adversely affected, the fish and shellfish that eat the plankton organisms will also be affected (see Figure I in Estuarine Productivity). Curiously enough, various species of fish feed on the low cordgrass marsh. Mullet (Mugil cephalus), munmmichogs (Fundulus heteroclitus) and juvenile sport fishes such as the red drum (Sinp occelatus) are known to 27 feed over the marsh on high tides. Resident species such as mummichogs, sheepshead minnows (Cyprinodon variegatus) and striped killifish (Fundulus majalis) all can be found over the marsh on high tides. In addition, researchers here in Delaware have some preliminary evidence that the mummichog lays its eggs on the base of cordgrass (S. alterniflora) stalks on high tides during the spring and summer. All too often, man has interacted with the wetlands with only a few of the functions of these systems in mind. Marshes were ditched to reduce mosquito populations, but these practices also led to unplanned reductions in larger invertebrate, bird and mammal populations. Impoundments have been constructed which increase animal usage of wetlands but which interrupt estuarine nutrient cycling,ultimately affecting phytoplankton, zooplankton, fish and shellfish populations. In undisturbed areas there seem to be few conflicts among the many ways in which wetlands can serve animal populations. The interactions are so subtle that we really have little insight into their complexity and interpre- tations. However, it is when the balance has been upset in the disturbed areas that the extent of the perturbations of the wetlands becomes apparent. Often, impact becomes more apparent when we try to restore the balance, finding instead that simply reversing the nature of our interferences with the wetlands leads to even more disruptions of these systems. This is occasionally the price we pay for acting unwisely in the first place. As it stands now, few areas remain undisturbed and it is therefore more imperative than ever that all the animals that use the wetlands be accommodated in all further wetlands-estuarine manage- ment plans. 28 THE RELATIONSHIP BETWEEN WETLANDS AND ESTUJARINE WATER QUALITY The title of this section is somewhat vague and therefore open to interpretation. What is meant by the terms"relationship" and "water quality'? "Relationship" was interpreted as meaning both how the wetlands affect water quality and how water quality affects the wetlands. "Water quality" includes the factors of sewage loading, silt content, heavy metals, pesticides, oil pollution and thermal pollution. Dissolved oxygen and salinity were omitted from consideration under water quality despite their obvious importance. Both are discussed in the Marine Habitat-Environmental Parameters section. Dissolved oxygen is Influenced by sewage loading and the resuspension of sediment. Salinity is altered by man when dams and flood gates are used to restrict stream flow (See Wetland Destruction section). Silt Estuaries are characterized by muddy bottoms that are continuously being added to by deposited sediments. The organic and inorganic material that constitutes silt can originate from river input, shore erosion, resuspension from the bottom, waste disposal, dredging and spoil deposition activities. Inorganic particles can be rock and mineral fragments such as quartz, feldspar or mica. The organic material can be considered detritus, the origin of the detrital food chain. Silt particles can also be a combination of inorganic particles covered with microorganisms. Silt particles have the ability to absorb many materials including nutrients (nitrates, phosphates, etc.), heavy metals, radionuclides, pesticides and oil products. Silt and sediment can affect the biota in a variety of ways. Heavy 29 silt loads can smother nonmobile benthic organisms, eggs and larvae. Less severe loadings can impair gill respiration. Particles suspended in the water can impair light penetration and thus reduce primary productivity by limiting the depth of the water column in which the rate of photosynthesis exceeds respiration. Resuspended sediment that is coated with organic material can exert an oxygen demand that Is higher than that of the same material in bottom deposits. Silt loads can also affect plant growth by absorbing nutrients, but the mechanisms of absorption are complicated and as yet not fully understood. Marshes effectively function as sediment traps. Water current velocity in marshes is typically quite slow and this allows silt to settle out as sediment. With each high tide that floods the marsh surfacemore sediment is deposited. The result is a slow, continuous build-up of the marsh. By absorbing various materials, silt can act to concentrate nutrients, trace metals, and toxic pollutants as it settles onto the marsh surface. The basic relationships between physical and chemical apsects of suspended and deposited sediments and the responses of estuarine organisms are poorly understood. Particulate matter affects the growth, survival or reproductive aspects of estuarine organisms both directly and indirectly at the organisms' several life stages. Evaluation of the problem is further complicated by the different sensitivities of life stages to varying conditions of temperature, salinity and dissolved oxygen. The observed responses of organisms may not be due to either turbidity or suspended sediment concentrations, commonly expressed as extinction values or tons/day or mg/i, but rather to their size distribution, shapes, types, presence of organic matter, metalic oxide and organic coatings, or the adsorptive properties of the particles. Because of its commercial value, the American oyster (Crassostrea virginica) has been studied relative to various sediment loads. The earlier 30 life stages of the oyster are more sensitive to sediment loads than adults. Severe larval mortality occurs in concentrations of suspended material above 100 mg/I. This same concentration caused a drastic decrease in the adult pumping rate, but no significant adult mortality was observed. Prior to any wetlands/estuarine project that will produce increased sediment loads, the following aspects should be investigated: 1. The range and types of particles to be resuspended and transported, where they will settle, and what substratum changes or modifications otherwise created by project activities will occur in the dredged and disposal areas. 2. The biological activity of the water column, the sediment-water Interface, and the deeper substrate material which often houses burrowing organisms. 3. The release into the water column of sediments, those substances originally dissolved or complexed in the interstitial water of the substratum, and those beneficial or detrimental chemicals sorbed or otherwise associated with particles which may be released wholly or partially after resuspension. 4. The relationships between properties of the suspended load and the permanent or resident species of the project area and their ability for and dynamics in repopulation, and the transitory species which use the project area only at certain seasons of the year. For more information see Agriculture, Spoil Disposal and Environmental Requirements. Sewage Due to their proximity to population centers, estuaries often receive the effluent from municipal sewage plants and individual septic-field leachate. Municipal sewage is treated in three steps -- primary, secondary and tertiary. Primary treatment removes the solids and with them some of the biological oxygen 31 demand (B.O.D.) load and heavy metals. Through the oxidation of organics, secon- dary treatment removes the organics and most of the remainder of the heavy metals. Tertiary treatment removes the inorganic nutrients such as nitrates and phosphates. Currently in the State of Delaware most sewage treatment plants provide secondary treatment. A few plants provide only primary treatment of the sewage, while at present there are no tertiary treatment plants. Several damaging effects can result from excessive sewage loading. The dumping of raw or primary treated sewage can result in reduced,dissolved oxygen levels. Municipal sewage that includes industrial input contains heavy metals that are not completely removed even by secondary treatment. Dumping of all sewage except for tertiary treated material results in increased nutrients and therefore possible eutrophication. Raw or improperly treated sewage can cause increased fecal coliform bacteria counts. It is generally agreed that marshes and estuaries are not suitable for treating raw or primary treated sewage. Marsh systems already have naturally high B.O.D.Is due to their high organic content and thus cannot handle additional organic loading. Some investigations have pointed to the marshes as sources of organics due in part to the excreta of the resident wildlife and waterfowl. An exception to the unsuitability of marshes for primary or secondary water treatment was revealed in a study of the Tinicum Marsh near the Delaware River in Pennsylvania. Analyses of water taken before and after covering the marsh surface showed that the marsh decreased the B.O.D. levels in 57 per cent of the samples and increased the dissolved oxygen in 73 per cent of the samples. Municipal sewage systems that have industrial waste input have high levels of heavy metals. Over half of the heavy metals are removed by primary and secondary treatment, but that still leaves considerable heavy metal discharge for those systems receiving Industrial wastes. The relationship of heavy 32 metals to the marsh are discussed In the next section. High discharge rates of secondary treated sewage can increase the inorganic nutrient levels and thus cause eutrophication of estuaries. The term eutro- phication is widely used, but not accurately defined. In an estuary, eutrophication means an increase in nutrient supply. Nutrients might be considered the primary cause of eutrophication by definition, but the symptom or effect is expressed as an over-abundance of plant biomass. It is important to note that most estuaries are eutrophic but not necessarily out of ecological balance since the grazing segment of the community may be well adjusted to the system. Artificial enrichment is usually referred to as cultural eutrophication. Information on agriculture's contribution of nutrients from field runoff is discussed in the Agriculture Section. Some researchers believe the marsh is well suited for tertiary treatment of waste water already secondarily treated. This appears to be a possibility because the marsh system is an active system that can store and recycle nutrients with great efficiency. Tertiary water treatment is the most expensive treatment step if done by man, so marsh lands could have great value if used as tertiary treatment areas. Unfortunately, the large areas of marsh required to absorb the nutrients are not available. Even though we are fortunate that eutrophi- cation of estuarine areas from municipal sewage inputs appear to enhance rather than harm productivity of marsh grasses, the bounty is not so great that the tertiary treatment of wastes from coastal cities will come cheaply. Fecal coliform bacteria in sufficiently high concentrations can cause the closinq of estuarine areas to shellfishing and bathing. Improperly treated sewage can raise the coliform bacter ia count to levels above the State criteria for primary recreation which is 200 cells/100 ml. of water. The wildlife, especially waterfowl, that rest and feed in the wetlands add to the background 33 coliform count. The Leipsic and Broadkill Rivers have elevated counts partially because of the Bombay Hook and Prime Hook Wildlife Refuges respectively. Bacteria counts in excess of water quality standards is a major surface water quality problem in Delaware. Three major problems are exacerbated by sewage input -- B.O.D. loading with resultant lower dissolved oxygen levels, increased nutrient loading and increased fecal coliform bacteria counts. Marshes may be able to lower the B.O.D. levels and raise the dissolved oxygen (0.0.) levels. They can remove moderate amounts of nutrients introduced from sewage outfalls, but unfortunately, the marshes contribute to the bacteria problem rather than improve the water quality of rivers receiving sewage treatment plant effluent. Heavy Metals Heavy metal pollution is an aspect of water quality that can be associated with sewage effluent. Heavy metals (generally those metals heavier than iron on the Periodic chart) are not a concern when they are present in normally low levels, but when the concentration levels are increased as a result of a man- made input, heavy metals can become dangerous (such as the methyl-mercury poisoning in Japan). Heavy metals are also of concern only when they are available to organisms, normally in the form of ions or complexed with organic molecules. The addition of heavy metals to an estuarine system is of particular concern because heavy metals are not degradable and therefore have a long life- time. Also, physical, chemical and biological processes within estuaries and wetlands may combine to concentrate these materials. Physical processes include sorption onto suspended solids, sedimentation, current dispersion, turbulent dispersion, and resuspension of sediment. The chemical processes within the estuary including ion exchange, complex formation, 34 chelating flocculation, and coprecipitation are poorly understood. The biological processes on the ecosystem or conmmunity level involved in heavy metal cycling and concentrating are also very poorly understood. Sources of heavy metals can be classified according to the type of source. Point sources include industrial and municipal outfalls, dumping sites and dredging projects. Diffuse sources include agriculture runoff, urban runoff, and scrubbing out of air pollution. The effects of high levels of heavy metals on wetlands organisms manifest themselves in three basic forms. Extremely high levels cause direct acute toxicity and "kills". Somewhat lower levels cause indirect food chain effects wherein lower trophic levels are reduced thus resulting in reduced food for higher organisms. Lastly, lower levels of heavy metals result in chronic toxicity which causes reduced growth, viability, reproducibility and increased susceptability to diseases. Organisms such as clams, oysters and crabs exposed to elevated levels of heavy metals can also be dangerous when consumed by man. The probable sources and deposition areas of trace metals adsorbed onto fine-grained suspended material in Delaware Bay have recently been described. Silt as suspended sediment originates from the Delaware River, eroded from tidal marshes, and from the ocean. This suspended material with its attached heavyv metals is then deposited in the ship channel and along the shoreline especially in the area between Port Mahon and the St. Jones River mouth. The Delaware River was found to be the primary source of iron, zinc, lead, cadmium, mercury, and nickel while the ocean was the primary source of magnesium, chromium, copper and strontium. The currents in the bay were found to be the main factor influencing the distribution of all these metals, irrespective of their source area. Sediment is constantly being deposited on the marsh surface when high tides flood the marsh. Since heavy metals are attached to the silt particles, 35 deposition of sediment on the marsh also serves to concentrate heavy metals. Approximately half of the mercury entering the estuary on silt particles ends up in the sediment. Plants in the marsh accumulate the heavy metals which have been deposited on the marsh surface. When the plants die and enter the water as detritus, they carry with them the accumulated metals. Thus animals feeding on detritus rather than phytoplankton consume higher levels of heavy metals such as lead and mercury. Once consumed, heavy metals are slow to be released. For example, a northern pike held in high levels of methyl mercury released almost no mercury over a period of one year following transfer to clean water. Data on direct,acute toxicity to heavy metals in estuarine animals is limited in scope and volume. The soft shell clam has been tested for acute toxicity to cadmium; the blue mussel, Mytilus edulis, has been tested for mercury, copper and cadmium. Little or no data exists on acute toxicity for the blue crab, Callinectes sapidus, or for most sport and commercially valuable fish. The American oyster, Crassostrea virginica, has been tested for cadmium and lead poisoning. Oyster larvae were found to be 14 to 1,000 times more susceptable than adults to mercury, copper and zinc. The reported suscep- tability of oyster larvae is characteristic of many estuarine organisms. It is ironic that the life stage most susceptable to metal poisoning is the stage that uses the estuaries for nursery and feeding grounds. Data on the chronic effects of low heavy metal concentrations is most essential for assessing long-range ecological trends, and more research is needed on this critical subject. So little is known about the complicated biochemistry of heavy metals that it is impossible to state what levels of each metal are dangerous, toxic, or lethal for the many estuarine organisms. The bioavailability of heavy metals can be altered by changes in salinity, pH, dissolved oxygen, temperature, 36 currents, or any combination of factors. For example, decreased pH supresses the sorption of copper, lead, and zinc onto particulate matter; and increased temperature, as in the thermal plumes from a stream electric plant, increases the availability of heavy metals from suspended sediments. The susceptability of organisms to trace metals in addition to the bioavallability is also in- fluenced by many chemical and physical factors. Several species of isopods are more susceptable to mercury at decreased salinity and increased temperatures. The cycling of heavy metals in the estuary and wetlands is very complicated and as yet, poorly understood. However, several facts can be stated: 1) Heavy metals can be dangerous or fatal to estuarine organisms and man; 2) Trace metals are normally found in very low concentrations; 3) Elevated and poten- tially dangerous levels are still relatively low concentrations; 4) The marsh and its organisms are very susceptible to elevated levels of heavy metals because of the marsh's ability to concentrate the metals and also because of the larval forms' susceptibility to metals. Oil Pollution The wetlands in Delaware are vulnerable to any oil spill occurring in Delaware Bay or offshore. The seven major refineries located along the Delaware River require about 300 million barrels of crude oil each year when running at capacity. All of this crude reaches the refineries by ship, and roughly 15 per cent or 45 million barrels are transferred to barges or smaller ships in a process called lightering, prior to moving up the Bay. Offshore, tracts of the continental shelf will soon be leased to commercial oil interests for exploration. Specifically, there are several potential sources of oil pollution. There can be leaks during the lightering operations in the Bay. Spills can occur due to ship groundings or collisions. The cleaning of tanks and bilges can result 37 in oil discharges. Leaks during exploration or actual drilling offshore can occur. Finally, industrial waste discharge containing petroleum products can be a chronic source of oil pollution. The same characteristics that make the marsh vulnerable to other forms of pollution make it vulnerable to oil pollution: 1) the marsh is close to man's activities; 2) oil enters the sediment due to the constant deposition of particulate material; 3) the marsh and estuaries serve as spawning and nursery grounds to larval stages of many organisms that are high vulnerable to pollution stress; 4) the low, flat nature of the marsh surface is periodically covered with flood tides which can cover large areas with oil. Toxicity of oil pollution varies with the petroleum fraction involved. In a decreasing order of toxicity are gasoline, diesel, bunker C, and crude. The most toxic oil products have the largest percentage of volatiles, therefore, they become less toxic very rapidly as the volatiles evaporate. The process by which the composition of spilled oil changes with time is called weathering. Ironically, the detergents used to disperse oil spills are often more toxic than the spill itself. Weathering of an oil slick begins immediately and proceeds via several means. Depending on the temperature and wind velocity, the volatile fraction of a spill evaporates rapidly. Within twelve hours of a crude oil spill roughly 40 per cent is evaporated or in the water column while 60 per cent remains as a tarry slick. The oil can also be abraded by the sand on beaches or consumed by browsing invertebrates. The oil coats suspended particular matter and sinks to the bottom. The spill can be a source of energy for certain bacteria that are capable of oxidizing the oil. Thin layers of crude oil can be colonized by bacteria in two to three weeks and completely decomposed in two to three months. The effect of an oil spill on the marsh depends on the size of the spill, 38 the duration of the release, and the type of oil spilled. At the very least, the aesthetic values of the wetlands are decreased. The various habitats of the estuary and marsh if sufficiently modified can cause a decrease in the number of susceptible species and an increase in the number of tolerant species. A spill can cause a decrease in fishery and wildlife resources for years to come if juvenile stages are affected. A hazard to humans also exists through contaminated seafood. Prediction of a spill's severity is difficult because of many compounding factors. Fate of a spill depends on the prevailing winds, water current and temperature. Toxicity to an organism depends on the temperature, salinity and the life stage exposed. The tide stage at the time of the oil's entry into the marsh determines how much marsh surface Is covered by a spill. Also, the number of wildlife potentially affected by a spill changes with the seasons. Marsh grasses are the most obvious indicator of the high marsh productivity. A crude oil spill on the marsh can cause a die-back of the grasses within two to three days. The greatest area of the marsh is affected during a spring flood tide when the marsh receives the highest water. A die-back caused by the toxic fraction of a spill can recover by the following season, but the effects of seeds smothered by the oil can have lasting effects. Shallow water plants with small food reserves such as Salicornia are the least tolerant, while perennials with large food reserves such as Spartina and Juncus are more tolerant of oil pollution. Filamentous green algae is moderately tolerant but tends to be replaced by blue-green algae following a spill. Delaware's wetlands serve as a refuge for thousands of waterfowl each year. An oil spill that moves into a refuge area during the winter can spell disaster for thousands of ducks and geese. Since the oil is most damaging to waterfowl while it is in the form of a slick, the application of dispersants 39 before the spill reaches the refuge can reduce the damage to the waterfowl. The surface of an oil spill causes the natural oils in feathers to lose their waterproof properties; the birds get wet and die of exposure. Waterfowl do not recognize the danger of spilled oil and land in the slicks. Those species that are divers such as the common ducks become completely coated if they dive through a slick. Bird cleanup procedures have become more effective in recent years (from 5 per cent to 50 per cent survival of those cleaned), but the mortality is still very high since most birds die before they can be treated. Those species with low reproduction rates are the most vulnerable because of their lower capacity for replacement of those killed. There is considerable knowledge on the effects of spilled oil on adult oysters. It has been found that adult oysters are very tolerant of oil. Oysters pick up some of the fractions through ingestion of coated particles and may "taste" if consumed. A number of studies have shown that the oysters can eliminate the contaminants in ten to fifty days if the oysters are moved to clean areas. There is at least one reported instance in which oysters did not eliminate the oil, even after considerable time. Oyster larvae are much more sensitive to crude concentrations than are adults. If a spill occurs during the summertime when larvae are in the water column, a number can be killed outright. Larval distribution in the water is patchy and it would be difficult to estimate the effect of larval mortality on the fishery of the estuary unless one knew the area effected by the spill in relation to the total estuarine area and the total larval population. It is clear, though, that considerable mortality of larvae could occur in the affected area during the summer months. During the winter when commercial fishing for oysters is active, there can be considerable effect on the livelihood of fishermen in the area since 40 the adult oysters may pick up an unpalatable "taste" due to the oil, and the beds may be closed. Since some of the spilled crude may reach the bottom attached to sediment particles, the "taste effect" on adult oysters may last for a considerable time. Other estuarine organisms besides oysters are affected by an oil spill. Small invertebrates such as marsh crabs inhabiting the marsh surface can be smothered by the heavy oil residue. Mobile animals such as fish can escape to cleaner water. Oil enters the sediment to a depth of at least 70 centimeters through settling of oil-coated particulate matter and reworking of the existing sediment. Oil-decomposing bacteria are ubiquitous in the marine environment -- 4 x 108 individuals/ml of sediment were found along the Cornish coast following the Torrey Canyon oil spill. However, the anoxic conditions of estuarine sediments significantly retard bacterial degradation of oil. Contrary to common belief, no magnification of oil concentrations in higher trophic levels was seen in a recent study. The level of contamination depended on the characteristics of each organism rather than its position in the food chain. Discussion thus far has been concerned with the effect of oil pollution on the marshes and estuaries. Despite the scarcity of information on oil pollution in the marsh compared to rocky intertidal or sandy beaches, it appears that the marsh may have a positive effect on an oil spill. Due to the marsh's low surface, it can store and gradually release oil on successive high tides. The emergent grasses provide conditions favorable to microbial breakdown of oil in moderate quantities. Microbial breakdown of oil is enhanced by high D.O. levels, nutrient levels and temperature, all of which exist on the marsh surface. However, a heavy influx of oil onto the marsh can smother the bacteria and kill the grass thus reducing the ability of the marsh to break down the oil. In conclusion, it is strongly advised that if an oil spill occurs, it 41 should be prevented from entering the estuaries and marshes. An oil spill has the potential to kill thousands of waterfowl, contaminate shellfish, kill fish, crab and bivalve larvae, foul the bottom sediments, kill emergent grasses -- in short, disrupt the entire marsh ecosystem. The amount of damage depends on the size and type of spill, the season, the prevailing winds, plus the water salinity and temperature. Thermal Pollution Temperature is a critical aspect of water quality. It directly affects the rate of all chemical reactions whether within organisms or in their surrounding environment. Changes in temperature are also essential as clues to migration, mating and spawning behavior. The natural temperature regimes are being threatened by ever-increasing numbers of electric generating plants that use the water from rivers and estuaries to produce steam and then to remove waste heat. A complete discussion of temperature and thermal pollution is given in Temperature and Its Relationship to Estuarine Organisms. Pesticides Pesticides are of extreme potential harm to estuarine organisms. Pesticides washed into estuarine waters tend to "salt out" onto sediment particles and are deposited in estuarine sediments. Hence, pesticides become concentrated in estuarine sediments. Many marine organisms concentrate pesticides in their tissue due to biological magnification, i.e., many animals, especially shellfish, can selectively remove pesticide type materials from the environment and store them. Biological manification of harmful substances (DDT, PCB, toxaphene, dieldrin, kepone) can cause lethal and sublethal effects in estuarine animals and those who consume them. In Delaware, a pesticide survey completed in 1969 showed that three species 42 of shellfish throughout Delaware had relatively moderate concentrations of DDT and its metabolites, and dieldrin. Delaware did not seem to be harmed significantly by these pesticides, now restricted by the federal government. However, as citizens of this state, we must take care and insure that adequate measures are taken to prevent pesticide pollution disasters in Delaware. For a detailed discussion of pesticides, see Agriculture. Six main topics have been treated in this section on estuarine water quality. It is hoped that the interdependency of these factors and complexity of the estuarine/marsh system is appreciated. While some aspects of water quality are well understood, the complexity of water chemistry has made a complete understanding of the processes impossible thus far. It is fairly safe to say, however, that perturbation of one aspect such as temperature would cause repercussions in other aspects of water quality. References Bopp, F. and R. B. Biggs. 1972. Trace metal environments near shell banks in Delaware Bay. Delaware 1975 State Water Quality Inventory. 1975. DNREC, Division of Environmental Control. Flemer, D. A. 1972. Current status of knowledge concerning the cause as biological effects of eutrophication in Chesapeake Bay. Ches. Sci. 13 (Supplement): 144-149. Frazier, J. M. 1972. Current status of knowledge of the biological effects of heavy metals in the Chesapeake Bay. Ches. Sci. (Supplement): 149-153. Grant, R. R., Jr. and R. Patrick. 1970. Tinicum marsh as a water purifier. In: Two studies of Tinicum Marsh. The Conservation Foundation, Washington, T.. C., 123 pp. Leland, H. V., E. D. Copenhaver, and D. J. Wilkes. 1975. Heavy metals and other trace elements. J. Water Poll. Contr. Fed. 476: 1635-1656. Nixon, S. W. and C. A. Oviatt. 1973. Analysis of local variation in the standing crop of Spartina alterniflora. Bot. Marina 16: 103-109. Odum, E. P. 1973. The pricing system. Ga. Conservancy 1973(4): 8-10. 43 Petroleum in the marine environment. 1975. National Academy of Science. Washington, D. C., 107 pp. Proceedings of joint conference on prevention and control of oil spills, 1973. American Petroleum Institute, Washington, D. C. Sherk, J. A. 1972. Current status of the knowledge of the biological effects of suspended and deposited sediments in Chesapeake Bay. Ches. Scd. 13 (Supplement): 137-144. THE ROLE OF WETLANDS IN ESTUARINE HYDRAULICS Of the many subject areas covered within the Wetlands Atlas, this topic is probably the least understood or investigated. Virtually no information is in the literature, and discussions with experts in estuarine circulations also produced only limited information on the role of wetlands in estuarine hydraulics. It appears that of the wetlands areas, only the marshes have an effect on estuarine hydraulics. Because of their low elevation, marshes are able to absorb the energy of spring flood tides and storm surges as they cover the marsh surface. The absorption of energy is principally accomplished through friction between the marsh surface together with its emergent grasses and the thin sheet of advancing water. It is also felt that marsh peat readily soaks up floodwaters thus reducing their damaging effects. Usually marshes are able to absorb the energy without noticeable damage, but extensive damage to the vegetation can be sustained in cases of extreme weather. The marsh grasses along the Gulf Coast were uprooted and carried away by hurricane Camille. A year following the storm some marsh species still had not recovered, and the overall plant cover was still less than before the hurri cane. There exists a general transgression of the sea onto the land caused by a combination of the rising sea level and subsiding land. These two factors 44 cause coastal erosion on most beaches and marshes fronting the Bay and Ocean. As sediments are torn away from the edges of marshes they are redeposited by tides on the top of the marsh. The marsh grasses are primarily responsible for "trapping" the sediment. As the surge slows whole passing over the vegetation on the marsh surface, the suspended silt settles onto the marsh. The marsh, then, acts as a buffer by protecting upland areas by absorbing storm surge energy and in turn is built up by acting as a sediment trap. The end result is that a long-term shoreward and upward movement of marshes and beaches is occurring along the bay and ocean margins. References Chabreck, R. H. and A. H. Palmisano. 1973. The effects of hurricane Camille on the marshes of the Mississippi River delta. Ecology 54(5): 1118-1123. Silberhorn, G. M., G. M. Dawes and T. A. Barnard, Jr. 1974. Coastal wetlands of Virginia. Interim Report Number 3. VIMS, Gloucester Point, Virginia, 53 pp. 45 DEFINITION and / CLASSIFICATION of WETLANDS DEFINITION AND CLASSIFICATION OF WETLANDS DEFINITION OF WETLANDS Defining wetlands in an ecologically significant manner that is also applicable to legal delineation is difficult. Recent concern over wetlands destruction and ownership, however, has necessitated that an ecologically sound but legally practical solution to the problem of delineating wetlands be found. Therefore, states have developed various definitions of wetlands that include ecological validity and provide a, base by which the delineation of wetlands from uplands can be implemented from a legal point of view at a reasonable expense. Hawkes (1966) summarized some criteria used for defining wetlands: 1) presence of underlying peat; 2) position of land-water interface; 3) tidal elevations; 4) vegetative zonation; 5) level of nutrient production, and 6) soil salinity. There are many problems associated with defining wetlands by these criteria'. 1. Local tidal level information is limited. 2. The datum lines of mean low water (MLW), mean high water (MHLI), extreme high water and mean sea level (MSL) are not consistent. Mean high water as defined by the U. S. Coast and Geodetic Survey requires nineteen years of observations. Accuracy is very important since a difference of only .1 feet in MHW can mean several hundred feet of associated flat land lost or gained. 3. Correlation of tide data with land topography is difficult. 4. Using physical parameters alone to describe wetlands is risky since a very complex and varying set of physical factors combine to make a wetlands area. 47 5. Boundaries based on physical factors do not take into account the concepts of nutrient and energy flows, primary productivity, etc. (One of the principal values of wetlands is their biological productivity.) 6. Vegetative zonation is ambiguous in transition zones between wetlands and uplands. The characteristic species from each habitat grade into each other. 7. The level of nutrient production criteria would require extensive field work and tends to ignore other values of wetlands. 8. The soil salinity criteria would be only useful for wetlands adjacent to saline water and would require extensive field work. In 1963, Massachusetts became the first state to enact legislation control- ling the use of coastal wetlands. In 1965, Rhode Island passed its wetlands legislation. Maine and New Hampshire effected dredging and filling legislation in 1967. In 1969, Connecticut passed the first laws requiring an inventory of wetland areas. The states of New Jersey, Maryland, Florida and Virginia all enacted wetlands legislation in 1972. In 1973, Delaware effected its Wetlands Act and New York passed its Tidal Wetlands Act. The marked differences in the definition of wetlands in each state's law mean large amounts of land are included or excluded from wetlands legislation. Definitions can be 1) a very general description; 2) a list of vegetation and presence of salt marsh peat; 3) a list of vegetation and a specified height above a tide marsh; 4) a combination of one through three. The several states using definition three list from thirteen to seventy-four vegetative species in addition to any one of several heights above mean high water or mean low water. Lagner (1975) in a review of wetlands legislation concluded that "...vagueness, all-inclusiveness, ambiguous terminology, and difficulty in delineating boundaries 48 combine to weaken the power of wetlands legislation". The following definitions of wetlands illustrate this point: Massachusetts -- any bank, marsh, swamp, meadow, flat, or other low land subject to tidal action or coastal storm flowage and such contiguous land as the commiissioner reasonably deems necessary. Rhode Island -- the presence of any of certain plant species (19 species) and the occurrence and extent of salt marsh plant at the undisturbed surface. Connecticut -- (an) area whose surface is at or below an elevation of one foot above local extreme high water; and upon which may grow or be capable of growing some, but not necessarily all, of the following: (74 species including those of freshwater wetlands). A confusing definition of wetlands is found in Maryland's Wetland Act of 1970. It defines "state wetlands" as: all land under the navigable waters of the state below the mean high tide which is affected by the regular rise and fall of the tide. Private wetlands are defined as: all lands not considered "state wetlands" bordering on or lying beneath tidal waters, which are subject to regular or periodic tidal action and which support aquatic growth. These examples show that definitions are inconsistent between states, and in themselves ambiguous, and sometimes indeterminable. Many of the species lists contain plants that could grow in places other than a salt marsh or on land contiguous to a salt marsh. How is "extreme high water" determined in Connecticut? The wetlands defined as 3.5 feet above MHW (New Hampshire), 49 or 1.5 times the mean tide range at the site (Virginia) appear to be almost arbitrary definitions. Wetlands legislation in order to be effective must have definitions that are clear and concise. Further, states must be able to reasonably apply their definition of wetlands to the wetlands such that they can, in fact, be delineated from non-wetlands. Only in this way can the legal regulations be enforced. Delaware made its contribution to wetlands legislation in 1973. According to the Wetlands Act (Delaware Code, Chapter 66), "Wetlands shall mean those lands above the mean low water elevation including any bank, marsh, swamp, meadow, flat or other low land subject to tidal action in the State of Delaware... whose surface is at or below an elevation of two feet above local mean high water, and upon which may grow or is capable of growing any but not necessarily all of the following plants"...(see Table 1). "Further, the secretary of the Department of Natural Resources shall inventory, as promptly as he is able, all wetlands with the State..." Although Delaware's definition of the wetlands uses both the physical parameter of 2,0 feet above MHW and characteristic vegetation, the actual delineation of the wetlands based on the Acts' definition has proved to be expedient, relatively inexpensive and quite accurate. This is due principally to the twenty-nine species of plants which have proved to be a comprehensive listing, at least for Delaware, of all the dominant species which grow almost ex- clusively in the wetlands. Thus, detection of these plants is tantamount to legally delineating wetlands. Also, successful analysis of wetlands through interpretive aerial photography by other states has proved reasonable and in- expensive. Thus, from 1973-75, an inventory of the State was made by photo inter- pretation based on the twenty-nine species listed in the Wetlands. Act. In addition to indicating the upland boundary, the use of vegetation also provides information 50 about the ecological characteristics -- as community associations, primary production, and associated wildlife throughout the wetlands. Once the photo inventory has been accepted as the official delineation of the wetlands following public hearings, the two-foot elevation above local mean high tide will not apply to any area outside the designated wetlands area. Delineating the upland boundary of wetlands vegetative zoning, as stated earlier, can cause problems (refer to page 48, number 6). However, in delineating the upland boundary, the maps take a conservative line. That is, in every case, the most shoreward wetlands boundary delineated on the maps is below the two-foot mean high water line. Thus, absolutely no "Uplands" are identified as wetlands on the maps, although it is possible (and highly probable) that some wetlands may have been "left out". In addition, the transition marshes in Delaware are, fortunately, relatively narrow. At this point, Delaware has taken a giant step toward establishing a bank of sound management procedures through which to guard her wetlands. All but a very few minor activities designed for wetland areas must first come under close scrutiny of the State through the Department of Natural Resources and Environmental Control. Also, many activities which have proven to be deleterious to the wetland and estuarine flora and fauna in the past have been outlawed outright (e.g., the dredging of dead-end lagoons, unless aerators and water circulators are used, - DNREC, January 19, 1976). The legislation and final adoption of regulations is almost complete. It remains to be seen whether effective implementation of the legislation can be carried forth. 51 TABLE 1 A List of the Commom and Scientific Names of Those Species of Plants Used to Define and Delineate the Wetlands of the State of Delaware According to the Wetlands Act of 1972. Common Name Scientific Name Black Grass Juncus jerardii Bladder Wrach Fucus vesiculosis Cattail (Broad leaved) Typha latifolia Cattail (Narrow leaved) Typha angustifolia Dwarf Glasswort Salicornia bigelovii Eel Grass Zostera marina Groundsel Bush Baccharis halimifolia Marsh Aster Aster tenuifolius Marsh Elder Iva frutescens var. oraria Mock Bishop's Weed Ptilimnium capillaceum Marsh Mallow Hibiscus palustris Orach Atriplex patula var. hastata Perennial Glasswort Salicornia virginica Sago Pondweed Potamogeton pectinatus Salt Marsh Fleabane Pluchea purpurascens Salt Marsh Cordgrass Spartina alterniflora Salt Marsh Grass Spartina cynosuroides Salt Marsh Hay Spartina patens Samphire Salicornia europaea Sea Blete Suaeda linearis Sea Blete Suaeda maritima Sea Lavender Limomuium carolinianum Seaside Goldenrod Solidago sempervirens Seaside Plantain Plantago aliganthos Spike Grass Distichlis spicata Switch Grass Panecum virgatum Three-Square Rush Scirpus americanus Torrey Rush Scirpus torreyi Widgeon Grass Ruppia maritima 52 References Delaware Code, Chapter 66, Sections 6603, 6607. DNREC, Proposed Wetland Regulations, Division of Environmental Control, January 19, 1976. Hawkes, A. L. 1966. Coastal wetlands -- problems and opportunities. N. Amer. Wildl. Conf., Trans. 51: 59-72. Lagna, L. 1975. The relationship of Spartina alterniflora to mean high water. 48 pp. Predominant Plants of Delaware's Wetlands The following plants are predominant in Delaware's wetlands. Other plants can be found in selected locations but those listed below are most common and can be useful in wetlands identification processes: CHECKLIST OF PLANTS* (Names after Chamberlain, 1951) Common Name Scientific Name (Genus and Species) Arrow-arum (Duck-corn) Peltandra virginica Arrowhead (Duckpotato, wapato) Sagittaria spp. Cattail Typha spp. Cordgrass Spartina spp. Cordgrass, Big Spartina cynosuroides Cordgrass, Salt Marsh Spartina alterniflora Groundsel bush (Marsh elder) Baccharis halimifolia High tide bush (Salt bush, Myrtle) Iva frutescens Marsh mallow Hibiscus palustris Pickerel weed Pontederia cordata Reed grass (Giant reed, Feathergrass) Phragmites communis Rush Juncus spp. Spike grass (Salt hay) Distichlis spicata Salt hay (Salt meadow grass) Spartina patens Three-square, American Scirpus americana Three-square, Olney's Scirpus olneyi Tide marsh water hemp (Pikebush) Acnida cannabina Wild rice Zizania aquatica *Many other species can be found in Delaware's wetlands; the above are the most predominant. Following are photographs of the major species as they are seen in the field. In some cases, close-up inserts of a single plant are included to aid in identification. 53 FIGURE 3 ARROW-ARUM Smyrna River (Peltandra Virginia) 54 FIGURE 4 ARROWHEAD Drawyers Creek (Sagittaria Spp.) FIGURE 5 CATTAILS Drawyers Creek (Typha Spp.) 56 FIGURE 6 lose'~~~~~~~~~~~~~~~~~K BIG CORDGRASS Taylors Bridge (Spartina Cynosuroides) 57 FIGURE 7 & W1 SALTMARSH CORDGRASS Taylors Bridge (Spartina Alterniflora) 58 FIGURE 8 :J~~~~~dP~~ GROUNDSEL BUSH (MARSH ELDER) Drawyers Creek (Baccharis Namifolla) 59 FIGURE 9 HIGH TIDE BUSH Little Creek (Iva Frutescens) 60 FIGURE 10 MARSH MALLOW Indian River Inlet (Hibisas Palustris) 61 FIGURE 11 PI CKERELWEED Red Lion Creek (Pontendria Cordata) 62 FIGURE 12 P1ICKERELWEED Red Lion Creek (Pontendria Cordata) 63 FIGURE 13 REED GRASS Near Army Creek (Phragmites Communis) 64 FIGURE 14 lt <V Doe RUSHDoe (Juncus Spp.) 65 FIGURE 15 SPIKE GRASS Little Creek (Distichlis Spacata) 66 FIGURE 16 "p - U. At -n-o -1-111. V/If M; 44'f,#1~~44jP~ . ,v~ h'"kt4tt~f~4~ 9.Cr '- A C~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - O�%.. S 49'f'~~~~~~~~~~~~~~~~~~~~~~~I g~~~~~~~~~~~~. <,/,Pi9F -;- i- ??V"-J" - 94 0, SL HAY.i Woodand- Bea ch -Sat aes Widlf 'Are 1" - , .V67 FIGURE 17 Jt THREE SQUARE Little Creek (Scirpus Spp.) 68 FIGURE 18 Aldo,~~~~ TIDEMARSH WATER HEMP Little Creek (Acnida Cannabina) 69 FIGURE 19 / P ii l 70 ~g.��,`i 4/ :e~ ~~7 -sZ /i r^ - WILD RICE Appoquinimink River (Zizania Aquatica) 70 WETLANDS CLASSIFICATION SYSTEM In developing a Wetlands Atlas for the State of Delaware, a Wetlands Classification System composed of eight zones was instituted. The classification system evolved naturally from extensive ground truth experience and color infrared aerial imagiery. The system is based on interpretation of marsh vegetation since it is the vegetation of the wetlands which largely creates the habitat, acts as a source of food for animals, recycles nutrients and creates a trap for sediments. Vegetation is an accurate and specific reflection of all the many complex physical and chemical factors that are acting in wetland areas. In addition, once a vecietative zone has been identified, qeneralizations concerning production, animal associations and value of the area can be made. Vegetation can be mapped easily, at low cost and with reasonable accuracy using color infrared aerial photographs. WETLANDS ZONES AND PROPERTIES The system used for classification of Delaware's wetlands is derived from natural associations of plants found in the field. There are six floral zones (Zones I-VI), and there are two zones (Zones X, Xi) which refer to areas that were once marsh but have since been reclaimed by man for construction or impounding, respectively. Each floral zone is based on "dominant" vegetation (i.e., one or two major species which cover at least 50 per cent of a contiguous wetland area) with the exception of Zone V, Transition Marsh. For instance, Zone I is a marsh or wietland in which 50 per cent of the area is of one 71 species, Spartina alterniflora, salt marsh cordgrass. Species which are also commonly found in the area are listed as Associated Species. In many cases, the associated species depend on the location of the wetland area being mapped. New Castle County cordgrass marshes have associated species that differ somewhat from those found in the cordgrass marshes of the Small Bay areas in Sussex County (see Description of Drainage Areas). Provided with a description of each wetland zone, a manager can more accurately evaluate and compare wetland areas. The evaluation will also allow the manager to weigh the costs and benefits of alternative uses for each area. Each zone is described in terms of seven general parameters: 1. Primary flora - Primary flora identifies the dominant species present in the zone. A dominant species comprises at least 50 percent of the zone. 2. Growth habit - Growth habit describes the actual appearance of the plant as it appears in the marsh. 3. Primary production - Primary production is the amount of plant material produced in a growing season and is expressed as grams of dry weight of plant tissue per square meter (area) produced in a year (gm(dry) m-2 m'l). An approximation of primary production is peak standing crop. The latter, based on a one-time sampling of a species when maximum growth has been achieved, is usually determined in August and is expressed as grams of dry weight per square meter (gm(dry) M'2). The term "detritus" refers to all the particulate organic matter derived from the decomposition of dead organisms, especially plants. In the process of decomposition nutrients are released, and these nutrients plus the detrital particles are moved out of and into the marshes by tidal action. These nutrients are a food source for micro-organisms and plants that form the base of the marine food chain. 72 Primary productivity and peak standing crop are important measurements since they determine how much detritus can become available for either peat accumulation or as a food source. In general, plants with high production values produce more detritus than do less productive species. The availability of detritus to the estuarine food web is also dependent upon the height of the marsh and the flushing rate of marsh streams. 4. Physiographic conditions - This term describes the location where the dominant flora can be expected to grow. Some species grow better at higher elevations and lower salinities than others. Physiographic conditions, then, describe where in a marsh the dominant species for each zone can be expected to be found. 5. Associated flora - Although most of the vegetative zones are dominated by one or sometimes two species of plants, there are, associated with each zone, other plants which are conspicuous to the observer. These species are listed as associated flora (see species pictures). 6. Associated waterfowl and wildlife - Waterfowl and wildlife are often attracted to a particular vegetative zone for food and/or shelter. For example, muskrats use cordgrass sterns for their houses and cattails for food, and several species of ducks feed on seeds from the marsh, while geese consume the roots of the three-square. 7. Biting flies and mosquitos - The production of biting flies and mosquitos varies with vegetative zone. Areas regularly flushed by the tides are generally poor breeding areas for the salt marsh mosquito but may produce large numbers of biting flies. Following is a list of the zones and associated vegetation, along with photographs of a typical example of each zone. 73 WETLANDS ZONES AND ASSOCIATED VEGETATION ZONE I. Cordgrass Marsh A. Dominant species - Salt marsh cordgrass (Spartina alterniflora) B. Associated species - Big cordgrass (Spartina cynosuroides) Salt hay (Spartina patens) High tide bush (Iva frutescens) Groundsel bush (Baccharis halimifolia) Spike grass (Distichlis spicata) C. Others, depending on location: Salt wort (Salicornia sp.) Three-Square (Scirpus sp.) Rush (Juncus gerardi) Marsh mallow THibiscus palustris) Spike rush (Eleocharis sp.) Giant reed grass (Phragmites communis) ZONE II. Salt Hay Marsh A. Dominant species - Salt hay (S. patens) Spike grass (D. spicata) B. Associated species - Salt marsh cordgrass (S. alterniflora) Big cordgrass (S. cynosuroides) Groundsel bush TB. halimifolia) ZONE III. Salt Bush Marsh A. Dominant species - High tide bush (I. frutescens) or, Groundsel bush (W. halimifolia) Salt hay (S. patens) or, Spike grass (D. spicata) B. Associated species - Big cordgrass (S. cynosuroides) Salt marsh cordgrass (S. alterniflora) Marsh mallow (H. palustris) Giant reed grass (P. communis) ZONE IV. Giant Reed Grass Marsh A. Dominant species - Giant reed grass (P. communis) B. Associated species - Generally, none. 74 ZONE V. Transition Marsh A. Dominant species - No dominants B. Associated species - Salt marsh cordgrass (S. alterniflora) Big cordgrass (S. cynosuroides) Giant reed grass (P. communis) Marsh mallow (H. p'lustris) Three-Square (cirpussp.) Cattail (Typha sp.J Wild Rice Zizania aquatica) Arrow-arum (Peltandra virginica) Pickerel weed (Pontederia cordata) Tide marsh water hemp (Acnida cannabina) ZONE VI. Arrow-Arum or Pickerel Weed Marsh A. Dominant species - Arrow-arum (P. virginica) or, Pickerel weeU (P. cordata) B. Associated species - Wild rice (Z. a uatica) Marsh mallow (I. palustris) Arrowhead (SagTttaria sp.) ZONE X. Lost Marsh (1937-38 to present) ZONE Xi. Impounded Marsh 75 ZONE I. Cordgrass Marsh Primary Flora: Salt marsh cordgrass (Spartina alterniflora, Loisel) Growth Habit: A stout, erect grass, with long smooth tough leaf-blades, and strong creeping rhizomes, usually growing in pure stands. Tending to occur in a tall form near the water's edge followed by a smaller dwarf form to approximately the level of mean high water. The surface of the marsh is usually clearly visible between individual plants at low tide. Primary Production: Value Measure Size Locale Source 445 g(dry)m2yr-1 mixed Canary Crk. Morgan, 1961 517 g(dry)m-2 short Canary Crk. Sullivan and Daiber, 1974 362 q(dry)m'2 short Canary Crk. Clark, 1975 1419 g(dry)m-2 tall Canary Crk. Clark, 1975 704 g(dry)m-2 mixed Murderkill Crichton and Fornes, 1973 Physiographic Conditions: Growing from mean sea level to approximately mean high water in saline to brackish water on a layer of peat formed from roots and accumulated muddy sediment. Secondary Flora: (Usually associated with spoil banks along drainage ditches and portions of the marsh above mean high water.) Salt hay (Spartina patens (L.) Greene), Big cordgrass (Spartina cynosuroides (L.) Roth), Spike grass (Distichlis spicata (L.) Greene), Salt wort (Salicornia sp.), High tide bush (Iva frutescens L.), Groundsel bush (Baccharis halimifolia-..), Reed grass (Phragmites communis Trinius), Marsh mallow (Hibiscus sp.) Associated Waterfowl and Wildlife: Canada goose, Black duck. Roots and rhizomes eaten by waterfowl such as Black duck, Green- winged Teal and leaves and stems eaten by geese and muskrats (along with root stocks). Stems used for muskrat lodges. Nesting material for rails and willets. Protective cover. Seeds eaten by several kinds of ducks, especially the Black duck. Biting Flies and Mosquitoes: Mosquito production varies in this zone, depending upon the frequency of inundation. In most cases, breeding is low in frequently flooded tall salt marsh cordqrass areas. Abundant breeding may be expected, however in areas of salt marsh cordgrass where the marsh surface is flooded less than eight days per lunar month. Greenhead flies (Tabanids) breed and develop in greatest numbers in the wetter parts of marshes. Most larvae are recovered in the regularly flooded cordgrass zone than elsewhere. One study ranked biting fly production according to vegetation in the following decreasing order: salt marsh cordgrass, big cordgrass and spike grass. Adult greenheads, however, tend to be found in the greatest numbers at the marsh uplands border. 76 Figure 20 4K;KV~~Si �It$#)jPY~4V?01 WUM >;m r muwn2U, '~~~~~ ~ ~ ~ ~ - - w~~~~~~~~~' ' '~~~~~ MUSKRAT HUTCH A,, NU"~~~~~~~~~~~~~~~~2 ApAll J~ ~ ~ ~ ~ ~~~~~ P,~22t AK S 22~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~%i 4k 011 " 2 4 A: <b4A,~~~32)VAAA S 2I1~o ~~222~~24~~ 2~~4;k t~ ~ 2~ t2 r 42 2 2222 2A2. A t'%4 r A , ~ (<j 2 452~~~~~~~4 ZON I CODG S M ARS Taylor Bridg 2 2 44A~~2 2 42~4~ 77 ZONE II. Salt Meadow Marsh Primary Flora: Salt hay (Spartina pat.en (L.) Greene) Spike grass (Distichlis spicata (L.) Greene) Growth Habit: Salt hay growing in dense yellowish-green mats, often resembles a meadow with swirls or "cowlicks". Spike grass, darker green and often growing along with salt hay but frequently occurring in dense, erect, pure stands, resembles a lawn with dense sods. Accumulated dead and decaying grass completely hides the marsh surface. Primary Production: Value Measure Locale Source S. patens 537 g(dry)m' Murderkill River Crichton and Fornes, 1973 908 g(dry)m'- Sussex County Reimold and Gallagher, 1973 0. spicata 629 g(dry)m'2 Murderkill River Crichton and Fornes, 1973 460 g(dry)m'2 Sussex County Reimold and Gallagher, 1973 Physiographic Conditions: Growing at elevations that are generally flooded only by tides that exceed the mean high level. Marsh surface formed of peat with less mud than the cordgrass zone. Secondary Flora: Salt marsh cordgrass along drainage ditches and in depressions. Big cordgrass growing in wetter areas often separating the salt meadow from the cordgrass. High tide bush and marsh mallow in the higher areas, and sometimes scattered throughout the meadow. Reed grass in small patches and near upland margins. Associated Waterfowl and Wildlife: A source of food in the form of seeds and root stocks for ducks, rails, geese and muskrats. Spike grass seed heads, young plants and root stocks are eaten by ducks and rails. Dense growth provides nesting cover for waterfowl, especially teal. Browsed by deer. Biting Flies and Mosquitoes: Being an area infrequently inundated and flushed and often with shallow pools of stagnant water, mosquito production in this zone is usually very hiqh. Conditions such as those that often occur in the salt hay are ideal for mosquito breeding. Biting fly production is less than that in the salt marsh cordgrass zone. Generally, the number of larvae decrease as the ground elevation increases from that of the salt marsh cordgrass zone. 78 Figure 21 railway 09 .3NMI" kl vr-d_~~~~~~~~~~~~,4 fals A ~~~~~~~~~~ >~~~~~~~~~~~~~~~~~45 I~~~~~~z; ~ ~ ~ ~ - (j~~~~ ~e a:~~~~~~~~~ NN ~ ~ K C,~~~~~ ~~~~~~79 ZONE III. Salt Bush - Salt Meadow Marsh Primary Flora: Salt bushes - High tide bush (Iva frutescens, L.) or, Groundsel bush ({B charis halimifolia, L.) Salt hay (S. patens) or, Spike grass (E spTcata) Growth Habit: Marsh surface densely covered with salt hay and spike grass as in Zone II but with numerous plants of either High tide bush or Groundsel bush. Primary Production: Value Measure Locale Source Iva frutescens 448* g(dry)m2 Sussex County Reimold and Gallagher, 1973 626* g(dry)m'2 Sussex County Reimold and Gallagher, 1973 Baccharis halimifolia -- -- -- -- *Estimated from living biomass. Physiographic Conditions: Very similar to Zone II but drier and usually occurring in closer proximity to the uplands. Represents the upper limit of the salt marsh. Secondary Flora: Salt marsh cordgrass and Big cordgrass near drainage ditches and wherever the marsh is wet and low. Marsh mallow tends to occur scattered throughout this area. Reed grass may occur in patches and at upland border. Switch grass (Panicum virgatum) can occur between this zone and upland, especially near fields and roads. Associated Waterfowl and Wildlife: Similar to Zone II due to abundance of salt hay and spike grass. It provides a nesting area for small birds and cover for a great variety of wildlife. Salt bushes themselves, however, provide no significant food value to the inhabitants. Biting Flies and Mosquitoes: Mosquito larvae are usually few in number in this zone, as there is little standing water and the soil is generally too dry. Similarly, few greenhead fly larvae are found. Adult mosquitoes and greenheads are frequently found in Zone III, however, because salt bushes frequently form boundaries between the marsh and uplands. 80 Figure 22 _'3'Allow MfI - V '6 412_1r__ CJ) ~~~~w LM5~ ~ ~ ~ ~~- 'Al '< , ~~7W', , -Rowj X~~~~~~ ~~~~~~~~e f ~ .~~~~~-. . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ " 3~~ ZONE III SALT BUSH-SALT MEADOW MARSH Grecos Canal 81 ZONE IV. Reed Grass Marsh Primary Flora: Reed grass (Phragmites communis) Growth Habit: Tending to grow in colonies of tall, stout, leafy plants with feathery terminal panicles or seed heads. Difficult to walk through due to the accumulation of dead stalks and leaves. Isolated colonies often form circular patches. Tending to take over and displace the original vegetation in marshes that have been disturbed. Primary Production: Value Measure Locale Source 1379 q(dry)m-2 Sussex County Reimold and Gallagher, 1973 1900 q(dry)m-2 Freeman Highway, Tyrawski, 1975 Lewes 1450 g(dry)m-2 Milford Tyrawski, 1975 861 g(dry)m-2 Murderkill River Crichton and Fornes, 1973 1812 g(dry)m'2 Blackbird Creek Crichton and Fornes, 1973 Physiographic Conditions: Growing at or above mean high tide and frequently colonizing disturbed areas such as spoil piles. Secondary Flora: Reed grass tends to grow in pure stands with essentially no secondary flora. Frequently, however, especially before reed grass has completely taken over a marsh, it occurs in circular patches of various sizes, which tend to merge with one another. In such cases, cord grasses may grow between these matches. Reed grass is often associated with transition zone plants. Associated Waterfowl and Wildlife: Provides cover and nesting area for wildlife but is of little direct food value. Biting Flies and Mosquitoes: Because of the deep litter layer characteristic of this zone, both mosquito and biting fly production is low. Where the giant reed is found along the edge of a marsh, adult mosquitoes and flies may be present in considerable numbers. 82 Figure 23 4''" g ""'> 2�4 '4" "'44< '>' NY "4 �t A 44 "'2 - .':jt' 4' 's - ''<'-42� &"' <'<"26 '4<> - 24 <242�2 "744,. tt '4444 'Ay' '4 4K4;<'"'" "<'� r 4' 442� (j) - N, " <'2<4' -\ "'' - -, N CD 44 4 '<'4 '4 '4 2444<44 Q 2� 4 4 '4< 7 Lii " '4'' "<'4 .4 4 ''7'""? ., '4 4""' '4 '4' A 2. m 4 4444' 4'<'< Y444<t4<-<4' <4 42' 4 '44.' t j %4< 2U< 'S4S <4 44'444j44"& "t-#- '4'- ''44< '<.4444<4 <<4 "4 444< "-'44424> '44 442444%4"K&t4<'4' '"'"-"' "' '� � N>' 'c. �'< '44" ZONE IV REED GRASS MARSH Thousand Acre Marsh 83 ZONE V. Transition Marsh Primary Flora: In general no single species dominates this zone but at the same time there is no sharp line of demarcation that separates it from the cordgrass zone or the arrow-arum-Pickerel weed zone. It occurs wherever drainage patterns extend far inland and water becomes essentially fresh. Wetland Species: Salt marsh cordgrass Big cordgrass Rush (Juncus spp.) Three-Square (Scirpus spp.) Switch grass Groundsel bush High tide bush Marsh mallow Cattail (Typha spp.) Arrow-arum P-eltrandra virginica (L.) Kunth) Pickerel weed (Pontederia cordata L.) Tide marsh water hemp (Acnida cannabina L.) Reed grass Wild rice (Zizania aquatica L.) Growth Habit: Highly variable depending on species present. Primary Production: Value Measure Locale Source Typha sp. 1565 g(dry)m'2yr-1 New Jersey Jervis, 1969 Mixed 1246 q(dry)m-2 Maryland Johnson, 1970 S. cynosuroides 1110 g(dry)m-2 Blackbird Crichton and Fornes, 1973 Z. aquatica 1547 g(dry)m-2yr-1 New Jersey Jervis, 1964 J. gerardi 180 g(dry)m-2 Sussex Co. Reimold and Gallagher, 1973 Physiographic Conditions: Very wet and still affected by tidal action. Salinity low. Peat substrate giving way to mud. Associated Waterfowl and Wildlife: Provides excellent conditions for many ducks, rails and for the muskrat for both food, nesting and shelter. Biting Flies and Mosquitoes: Production of the salt marsh mosquito Aedes sollicitans and of the greenhead flies is reduced inThis zone because of decreased salinities. The production of other less obnoxious mosquitoes is increased, however. 84 Figure 24 ~~~~~ ~~~~~~~7. oa~~~~~~~~~~ j LO~~~~~~ ID~ ~ ~ =;s J,~~~~~~, ZONE V TRANSITION MARSH St. Jones River, Dover 85 ZONE VI. Arrow-Arum - Pickerel Weed Marsh Primary Flora: Arrow-arum (Peltandra virginica (L.) Kunth) Pickerel weed (Pontederia cordata L.) Growth Habit: Erect closely spaced clumps of plants with broad heart or arrow shaped leaves and thick fleshy roots. Primary Production: Value Measure Locale Source P. virginica 160 g(dry)m'2yr'1 New Jersey Jervis, 1969 230 g(dry)m'2yr'1 New Jersey Jervis, 1969 P. cordata 63 g(dry)m'2yr-1 New Jersey Jervis, 1969 Physiographic Conditions: Tidal mud flats where the salinity is low and in freshwater. Secondary Flora: Reed grass often growing as fringe that separates this zone from the uplands. Marsh mallow growing at higher elevations throughout the zone. Arrow-head (Sagittaria sp.) in freshwater areas. Wild rice in areas of brackish to freshwater. Cattails may occur throughout this zone. Associated Waterfowl and Wildlife: Wild rice and arrow-head attract many species of ducks and the wood duck feeds extensively on arrow-arum seeds. Muskrats utilize cattails and arrow-head for food. Ritinq Flies and Mosouitoes: Little information exists on the numbers of mosquitoes and biting flies in these areas. The information available suggests that production of greenhead flies and marsh mosquitoes is low in these areas. 86 Figure 25 WAT ER ZONE VI ARROW-ARUM MARSH Augustine Creek 87 87 WETLANDS ATLAS (MAPS) Following is a set of wetlands maps showing the distribution of the various wetland zones. The imagery used in mapping the wetlands of the state was derived from NASA Mission 247 Roll 120, flown August 29, 1973, for the tidal wetlands and NASA mission 144 Roll 20B, flown August 23, 1970, for the Nanticoke drainage area. The original photos are nine inch color infrared and provide optimal discrimination of vegetative types. Mission 247 photos approximate a scale of 1/240,000 and Mission 144 approximates 1/60,000. In addition to the use of photographs, visits to field sites were carried out to obtain ground truth. This data was used to substantiate the inter- pretation made from the photos. The classification zones as determined from the color infrared photos were outlined onto reproduced aerial photomaps of the state dated March 28, 1973. Each photo map corresponds to the standard U.S.G.S. topographic map quadrangle. Classification zones as distinguished on the photomaps were also numbered appropriately. A word of caution must be raised regarding use of these maps. First, they are intended for management policy making, not regulatory use and should not be used for specific applications. Second, an official set of wetlands maps as required under the Delaware Wetlands Act of 1973 has been developed for the Department of Natural Resources and Environmental Control at a scale of 11=200'. It is this set which has regulatory (permit) application. Finally, the data base is limited somewhat by the age of the infrared photographs (1970 and 1973) and the date of the photomaps developed for U.S.G.S. quadrangle mapping purposes (1973 vintage). Accordingly, recent land development activities may have eliminated or modified some wetlands areas through filling, diking, ditching or paving. 88 -~~~~~~~~~~~~~~~~~~~~~ -Y "RITW ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~6 "Y' a/j ~* 4 ~' ~ - a 'av- ~~~~~~~~~~~~~~~X a-~~~~~~~~~~~~~AM aa-A~~~~~~A -r ~~ aa~W~Y Lild -A ~ - A -t, -a~~~~~~~g s'. k 4 w~~~~~4 -A WAR~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~aa V~~~~~~~~~~~~~ jr mm.~~~~~~~~~~~~~~~if -W , - go,~~~~~a - / a -~~~~~~~~~~~~/~~~~~$$~~~~~~K2~~~~~~~ii 4>~~~~~~~~~~~~~~I V Irg~~~~~~~~~~~~~~A - -a. -~~~~~~~~~~~~~~~~~~~~~~all accepts,,, ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ' 4 V;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~a A~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ a-'~~~~~~~~~'3 w,~~~~~~~~~~~~~ -A 4~~~~~~~~~~~ Wilmington South Figure 27 Generalized Wetlands Atlas~~~~~~~~~~~I - - FIGURE 26 WILMINGTON GENERALIZED WETLAND ATLAS P/ ; KEY MAP 8 MIDDLE- TOWN NOTE: These maps are for general management purposes only and should not be confused with the maps pre- pared under the Delaware Wetlands Act of 1973 which are much more detailed and used for regulatory purposes. The regulatory maps are maintained by the Department of Natural Resources and Environ- - 'SMYRNA mental Control. I4~ miueqadaeThe area shown in each photo is a U.S.G.S. 7.5 3 3 4 minute quaduarent. DOVER j 3'7" e SCALE IN MILES | fILFORD 39 0 41 1 42 4 3> 4XREHOBOTH s42. rR:~~~BEA-H SE1FORD F~qi 46 ~FRANKFORD I _9_ 89 g5q !W" IR~ M W ~m0O IN- it~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4,'4 elk~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~449�4 4 L~~~~~~~~~9 A.4~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 ~~~~~~~~~~~~~~~~~~~~~~~4 4I 44 � Delaware City Figure 28 Generalized Wetlands Atlas~~~99� VW~~~~~~~~~9 J-~~~~~~~~ v~~~- 7~~~~~~~~~~~~~~~~� J A ~~~~~~~~~~~~~~~~~~~~ 9~ mam~~~~~~~~~9 >'4'7 ~ 7'9'9l 9 '~~~~~ ~~4 A>'> &, -;< �>9>'~ I! ~� '"'''9, 49~~~~~~~~g "", R S~ ~ Nt' 9 4� > F~~~ Z "9 AXIZI~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A9~~~~~~~~~~~~~~~~~~~~~~~~~"f 9y 7~~~~~1 All~~~~~~~~~~~~~~~~~~9 9s 4 >99 '4 9> 9' )~~~~~~~~~~~~~~~~~~~1" $> 1 0 4 2> 7'9 Lft ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ /> ) g. '--mv,'9 -4q.~~~~~~~~~~~~~~~~~~TWSN =,>99, MIDDL9T9 /~~~~ ~~~~~A dll ( A>' 9' &'�>'>'� ~~~~ >t~tI�~~~� k"#'<~~~~ 47"'' 99 >9? ",'99' 99 > '<$' "� 999 >>A; A'>>~~~~~~P ">29 9> 99~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~N '99� '"" 9 9 9'~~~~~~~~~~~~A "a~~~~~~~i~9'''6 >' A>"'~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~m.V ' 4~~ 47< > '9>"' "A' '4'!~~0 >4 A4 r%9�'Y/t q>4'<'' 94,'~fti 9� 49>''">' '9. ~&> I "4r'~>"'"' 4949 '4"' 4/'94~<\�R 9 �'~~~�~~> > 9 >9> >4y A 994949 A9~~~~~~~~~~~~~%~~ %'9A9>4/A 44> 94>499~~~~-1'MI MideonFgre2 eeaiedWtad1ta i[?~~~~~~~~~~ T ~paay View al II i- ~$~~~~-Beach V,~~~~~~~~~~~~~~~8 P i~~~~~~~~~~3 -tl~~~~~~~~~~- Baltic~~~~~~~~~~~~: ; 5,~~~~~~~~~~~~~~~~~~�i ,,~~~V Vi; ~ t~~~~~~~~~~~~~~~~~~~~~~O aA 4 ID: i�~�:�o~~~_ �~40~r Talr rdeFgue3 eeaiedWtad ta %AAM 'MMSC,77r T x- ell", not, 14 V9 Chile -rol, g x v 1, M. MO A;M PM Y kwy x 0, % 4 WIZA KNE XPE 1, -s & tl 'i- 7 V M I- m IYO 60 !1L 1"- IIMM Za V voll A-Mu. Ab ,44J all o-, "A A lq FP,, IN IF- _ U11 A A we, A WIA MW . 1� ei,;, MM, -14 4ww MP"4; ro A, All.5 illegal 4h- '4 U X-1 R? 40:6 A "'o, I IM zp- V- 5s Ne, 'g "o- Smyrna Figure 31 Generalized Wetlands Atlas 4' '�~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 4~~~~~~~~~~~A J"~~~~~~~~~~~~~~~~>' I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~f 46~~~~~~~~~~~~ Bombay Hook Figure 32 Generalized Wetlands Atlas P ~~WA 04.~~~ V4>;~~~~~~~~~~~~~~A ~~~~~V 2, 44'S ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~t ps ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~~u Sr~ ~ ~~~ ~~~i CIId~ESWOLW' ' >' .1 -'54 , V.-> 4` V >~~~~~,, ~~~ ~ V '-''S~~~~~~~~~k C ;" i~'~' ~ 454)5445 ' . ~W$ + 2 90, sl44-S 4>4344544 445~~~~~~~~~~~~~~~~~~~A C'h~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~w In'~ NA~~~~~~~~~~'4445 Sj'44s` '->454 <,~~~~~ 45 all.4'>4> ' s :i h J~~~~~~~~~4 / NVI, -~~~~~~~~~~~~~~~~~~~~~~~~~ .44- 7, >444' 4444 C s O Y 4 > BLOW, t~~~~~~~~~~~p Z"N, ~~~~~~~~'t95'`V Dover Figure 33 Generalized~~~~~~~~~~~~"I WetladIta V Ar MW OM, 7729''I N 0 PI - v 3 Emery,,,' KENT kAfjD % WIV -4, Affi gL' 110 Al kx, gmk' OVA, -1110 j A V J-, A A U, N. R -5, I Ww'r 4' AP V mom P m Mahon 'its gg''p j "iff -PN 00H :%CREM !cut -O .j, J; h. 'M R OMAN, V 4 M1, JI, 0 Y- Little Creek Figure 34 Generalized Wetlands Atlas setiv' SpUje[1G~ p9Zi [eJOUGD~ S)Paj5H NT,~ ~ ' Ajj AAA AN4; IV~~~~~~~~~4~ 4'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4t 4~~~~~~~~~~~~~~~~~~~~~4 4'~~~~~~~~~~~~~~~~~4 <A' '"'N '% ' 4'>~~~~~~~~~~~~~~~~~~~~~c ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~N A~~~~~~~~~~~~~~~~~~~~~~~ 4MS4 'ell~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 04 'N>~~~~~~~~~~~~~A, 'N ~ ~ ~ ~ ~ '~.A'A 'F 10%, "WIPIP~~~~~~~~~~~~~~~~~~~~~~~~~F A > 4'NIA'N"N'AjJ K AN'~~~~~~AL 1 4' N~~~~~~~~~~~~~~~~~~~ 44~~~~ setiv spuellam Paz!le-lauag LPA5! ~O4[jl. A~~~~~~~~~~~~~~~" i �~~~~~~~~~~~~~~o 4~~~~~~Z~~ /~~~~~O\P~a NIZ~~~~~~ M~~~~~~~~~~~~~~- /~~~~~~ V~ Rt ank~~~~~srp RIAN ~ ~ 'K V ~~~~~~~~~~~~~~~~d 1~~~eOO41 ~~ - 4 I~~~~~~~~~~~~~~ ~~~~~~s:,a~~~~~~~~~~~~~~~a a''s;� - a 44~~ ~ ~~~~~~~ ~ ~~~~~~~~~~~ -~ -��: -� - - ..~~~~~~~~~~~~~~~~a fa ' a ~~~~~~~~~~~ia a~ a- - a 4 4a-'a - a a> i~~~49<a'e l aaaa~'a' a i: -4~~~~~~~~~~~~~~~- ~~-:~~~";a -::� a,,." a La~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ , aa 144 4 -gl~~~~~~~~~~~~~~~~~~~~~~aa4>,a a-4'a- a-on -l --a- ' --a a-a a Bennetts Pier Figure ~6 Gen&/4aia4. ata,>a' 4 t -- z,-Vff4'., le , sAt W7XI K IT" >4 0 C - fr-~~~~~~~~~~~~~~~A '5; 55;,P "Nt,4< T 7 OR~~~~~~~~~~~~~~>: 1'~~~~~~~~~~~~~~~~~~ Jim~~~~~~~~~7%%' ItW~~~~~~~~~~~~~~~~~~~~~Fwe ec 51~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1 "CA ~ ~ ~ ~ ~ ~ C Mispillion River Figure 38 Generalized Wetlands Atlas V~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~A A AN~ ~~~~~~~~~~~~~~~~~~~~~~~~<A 4 MI,> I - ~~~~~~~~~~~~~~~~~~~~A j A '"~~~~~~~n it "'�" "'<At I T A 15A~~~~~~~~ 9 A�A'W~~~~gA r~~~~~rg FDIC~~~~~~~~~~~~~~~~~~~~' "At~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~A A ~ ~ ~ ~ ~ ~ ~ <""'A'~~~~~~"met ama, ~~~~'S'AirA 0 " A N)~~~~~~~~~~ 4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 A ' A~~~~~~~~~~~~~~~~~~M P~~~~~~~~~~~~~~~~ii Rmit ' < '10~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~' A,,~~~~~~~~ it~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~a - I9N<A2<p"'C I&~~~~~~~~<~ �9 wX-0 '9 i!N ~ ~ ~ ilo Fiur 39Geealze etansAta a-.~~~~~~~~O 0~~~. 7 7 CI : 1 41~~~~~ Y, ~ I -~~~~~~ ~~~CC ~~~~~~~~~ ~~~oA~ CV~~~~~~~~~~~~~ N.W~~~~~~~~~~~~~~~~~~~~I I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~t Lewes Figure 40O Generalized Wetlands Atlas ""4 44 44 4 44 4 V '4 " '. 4 44 4'; 44 ;4'. 4 4 44 4444 4 44 4 4 '4' 4 4 4 4 1 '4> 4"'. 4444 444 44 44 -4��<' <4' <" 4 44 44' 44 <1 '4 4 4' '.4' 4>44' 4 44 444, 4 4 444 4 44444'.'4 4 '>4<> ,<%44/4, 44444 ,<4 44' <444744 � 44 "> ' I 44 4 4'.A" '<'4'. 444 444' 4 44 44>2<44 ''4 4' 44 ,>4 >444, 44 I 444' >444' 444 >7' " * 444< * 4444 <''4 44 4" * .9"'> 4444,.4444 4> 4"' 4 4'44,4444 44 444 44< 44444444444 44 4' 4 <>44444444444444> 4444 44 444444 4 4 ' 4"' 444>444444"' 44 44444 CAPE HENLOPE4 '444 4' <4 $TATE PARK 44444 ' 44' 444444 >< 4'. 444 4 4'4 4'> 444(4 44 444444 4444 - 4 44444"44 4" 7 44 1I'44+4A i< 4 <44 /i. 44" 44* '> 44444. 4 ] ><' 4' '44'44444, '4 1': 4< <'4444444 <4 / .4>' 4444444' 4> 444 '4 >' g'' ' ""4 4444>4 .444 44>4. 4 4 444<*,>' <4 4444444444444444 4>4444 ,44'.4 .>44 4444'> 4444444.44444< <4 >44444 4 44k>'<4'.4 > 4 444 '4444'4i">444444 4444 44 444 444' >4'>4 4>44>>> 4>444444144 '.44< >44 ' 4" 44<44 44 4.4 44> 44444444444 444 44 444494 44.4 4' 44444 '4 "4' '4 4<444 "44444<�"<Th4 '4. 44 444444 444444 44444444 44,44 4444 4>4>944'> 44 4444,4ff 44'4444 .'4 '444,4 44444'44444444 4 4'4444> 44444 4' p44444' "'<44444444>4444 44 44 44 4 4444<44 4 44 44 44 '.' 44 '. /44444444444 44<44'> 4 444.44 '44444>444'' 4444 4, 4444 44 4444 4444444 44 4 <'.>> 44444 444'4 4444' ' 4 74 4444. 44444>444444444>444 444 >44' 44444 44 444'. '444-44 44444444 '4 4<49 44444>4 Cape Henlopen Figure 41 Generalized Wetlands Atlas ~~~~~~~W, ~ ~ ~ ~ ~ ~ ~ ~ ~ , A~~~~~~~~~~~~~~~~ ~~~~~~~IA V_ .4~~~~~~~~~~~~~~~~~~~~~~~~~~" Alaska PO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'" j~~~~~~~ SEAFO~~7% C 3~~~~~~~~~~~~~~~~~~~~~~~~4 N O -4~> BLA~~~ES P 4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~P 4~~~~~~~~~~~~~~~~~~~~~~~~~4 4~~~~~~~~~~~~~~~~~~~~~~~~~~ 4 A-~~~~~~~~~~~~~~~~~~4 4>44 ow~~~~~~~~~~~~~~~~~~~)4 fa' ls ,ASeaor EatFgr 2 eeaie Wtad ta gg v- ~~~~~~~~~~~~~~~~~~~~AM "p, ~~~~~~~ ~ ~ > ~~~ J~~~~~~K ~ ~ ~ ~ ~ k C~~~~~~~~~~~~~~~~I -.~~~~~~~St M-, A ~~~~ j~~~~~~~~I~v CU~~~~~~~~~~~~~~~~~~~~~~~~*; %;g Faron iue 4 eeaiedWtad ta ~~~~~~~~WIN. -4 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~~~~~~- REHOSOT ~ ~ ~ ~ ,REt~oHBEC R~~~~~~~ehoey Beach Fiue4HeeaizdWtad ta 4~~~~~~~~~~~~44 4� - Th 44~~~~~~ ~~ ~~ 4, "M ai �~~~ ~~~~~ ~~~~~~~~~~~~ ~ I 'V4 I 4 I44. g 4# - O,�f S .~ Al, llil'.7 ; A- Or"16--,~~~~~~~~~~~~~~~~~~~~~~~~~~ 4444 j~~~~~~44~~4 4 44 4 ~~~~~~~4 4 �~~~~ 4~~~4<44s, Pi~~~~~~~~~~~~4 4 CIO 4 4 44 ~~44~~4, V 44 og, Z~4 4 444 4 444 4>,4 4444444144 4444 44 444 4 / 4 ~~~~~~~~4 444444i4 44Wp IAd'' 444 4444 4)4444 444~~~~~~~~~~~~~%, 4444 44)<:44 444.j4 V,~~~~~~~4444 4 4 44 ~~~~~~~44)44)W4444b)4 444 4h)4 )4 44>4 4 ~44<4 44/44/1>4444444 <4~44~44 f4 44444444 ~ ~ ~ ~ ~~ 114/4 4444 444 44 /444~~~~~~~~~Agol 44~~~~~444 jfMV ~444 4 /444444 4 4 4 4 . 4 < 4 4 4 4 4 4 4444444<4/4 4,444 4r 4)44/444444 g44444 ')d>;< 4 444 44444 j/# 4 44 44 444444 4))4/4 4 4 44 / ~ 44~ 4 4 44 4 4 44 4 4 44 4 > 4<4 44444444444 ) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~tg~~~~~~~~~~~~~~~~~~~~~~~~~~~444/44444 444444) 44444444444444 4444444 4 444 44444444444.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (14 4444;� 4444 44444444444444444444 444)44)4 44444 4 4 ~~44444444 444 ~ ~ ~~~~~ 4 ~ 4444 ;44 4 44._<444 - / 4' 4 . 444/r 4 44 444 444444444< 44444 44444144444444)4 / 'Q~~~~~~~~~44)4444 4444 444 44444 44444444 4 A m 4 4444-4 4 / 4 4 4 4 4~/ 4 4 444 44) 4)4 44444 44444~~~~~4 44 44N 011 444444444 2r41o4444 4 4444444444444,<4444 4 u4 44 44 '5~~~~~~~~~~~~~~~~~4 .. 4444 -P~ ~ ~ ~~444 )/4 444444444 7 /44, .4414. 41 44444 44 44444444444.44~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~3 4 ~ ~ ~ ~ ~~44444444 4 ~ ~ 4~A~ gp 44 444/4444 I 44444. 4~ 444444 <44444444444 4) 444444~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~gwv 4444<44<444 4444444<444 4444444~ )44<4444 444 44 ) 4 444 44 ~ 4 ) 44444 ~ 444, 4 4 ~ ) 4 444~~ ~~~~~~~~~~~~~~~~Sz, -44 VN4I 4 4 PhpI4/~4 444444444444444444) 444444 /44< ~ >~4444 44 44 ~4 4 Ir 444444444444444.P 4444 4444/44 44444444444444444 >4444) 4444444444 444444444 . N- CD~~~~~ 4 4 4 4 4 44444<4444444< 4 4 / 4 co~~~~~~44 /4 44444444 44444444.4 4. .4 4 4 44 444444) &~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~#4444 4444 .4 4444444~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4~~~~~Y 4~44444444~4)44 4444444>444 4'> 4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~44~~~~~~~~~~~~~~~~~~~.4~~~~~~~~~~~~~~~~~~~~44 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~% ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ f ~r 44 44 4< 44 < 4 444444444 44444 /444444 ~ ~ ~ ~ P 44 4) 44l 44444444.~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Ar444444 444 44444444<44444444 4 444444 44444 444( 4/44444/4444444444444)4444444444/4 \.4 /~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4444./4 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~44 4444444<4~ ~ ~ ~ ~ ~~~~~~~~~~~~~~~ I-.~~~~~~~~~~~~~~~~~~~~M --M, o >44.44444<~~~~~~~~~~~~~~~~i 44444444444 /4(4~~~~~~~~~~~~~~~~~~~~~~ p~~~~~~~~~~~~~~~44//4 44444)41 ~~~~~~~~~~~~~ ~ ~ ~ �T4444444 ~~~~~~~~~~~~~~~11 4 ~ ~ ~ ~ ~ ~ ~ ~ <4I~~~~~~~, 4 4~~~~~q 44444444444~~~~~~~~~~~~4! 444444444444444 ~ ~ ~ ~ ' 44444~, 1 4444 444 444444A 444444 4/44)4)4 44444444 44/4) 44/4/44444444444 4 /$4444474 4 44 44 4> 4 44 444 44 4 4444444 4444444444 ~~~~~~~~~~~~~~~~~~~~~~>~~~~,<4,<4444~~~~~~4 444444 444444~ ~~~~~ 44444 4 44 4 4) 44 44(4 4/44 4 444 ~ I4/44)44 4)4 4 4 4 ) ~> 4 4 �> ~ ~ ' < > 4 4 ~ 4 / 4 4 < 4 < 4 4 4 / 4 4 444P4 ~414 /4 444 4444444)44 44 j >4<4/4)444 ~ 4)4~ < >i 4 44)44444444444444 /4444444444> 4 44 4444444)44444/ 4 444444 44 4 4444 444444 ~4#~ 4~ > 444�444~4)44/4)4//4444444I 4) 4444~ 4 4)~4444 44 444444~ 44444>/44< 4)44�444� k >4) 444444444444 44 > 44/44444 44444 4~~~~~~~~~~<:4444>44 444444 ~ ~ ~ " 44444444~ ~ ~ ~ ~ ~ ~~ ~4~ v 444444/ 4 4444 444444 44 444444444 4444444 4 44444444444/4 4 >444>- tel 5,1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~444 44444444444 J~~~4444> kg; 441444444/( 4 <44444/4 ~ ~ ~ /4/4Oil 444444 4 > 4 4 44< 4 4 44444444 Sharptown,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~< Md.4 Figure4444 45 Geeaie4etad4ta N ~ ~ ~ ~ ~ N .�v~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~A v~~~~~~~~~~ % R-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Larl iur 6 eealiedWtlns ta ~ ', ~~~~~~~~~~~" < ' ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~uood, 'nM 44w".'.~~~~~~~~~~~~~~~~~~~~~~~~~~~tl 4 9O t 9 9 tiger~~~~9~9> .~ 9~994~, I bM~~~~~~~~99 < 94 1 ;9�~~99$ 4~~~~~~~~~~~~~~~~~~~~~~~~aw ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 99 4 9{~99999,9 -if~~~~~~~~~~~~~~~~~~~~~~~~~~~~9)99~94~ 9 M99 9 f999~,999~9 4~~~~~~~~~~~~~~~~~~~~~99 99>, 9~~~~~~~Tia,'"F /9999999~949, 999M* 4k9 9 99 091 9 '~'' ~ .,< <' <9 A~~~~~~~~~~~~~~~~999' ~ 99<99 9'9 9999 4i~ -' 9 99 9 9 99999999999~"~9 ~ <9999 9 <9994.999 99 99999999R99 ~59994~9999V99>9\ \9A~~ 999999999 9 9 ,99 M9 99999 9999 999999999 999999999 AU, ~ ~ ~ ~ ~ ~ ~ ~ '9>9999 9 9 ~ 99999 999~-4'999 <9~~~~~~ '~~~~~~: ~ ~ ~ ~ ~ ~ 9 ,~~~~~~~~~~9~~~~:'A L ~~~~~~~~~~~~~'99~~~f MM~~~~~~~;9 99999iN9I 9 99999999<99999999999999999999999999 999 9999 ~~~~~~~ 999999999999999 " <97- 99 ~ ~ ~ M 99 99999 999 99 9999999 999- 9959'9 99?9L ~9999 ~ 9 999 ;99)99)9999 ,99999' 999 ;2(99993�%j99Ur999 99999 ~ 9 99 999 99 999999 99<9 ~~~~~~~~~ 99R,9V99'9' 9999;9 99 39997 <99999 999~ ''9 99~999999999999, p9"' 99'9 < 9 999 999 99 A99 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ p 9999 99999 9 99W9999'9 99<99V9999999999 9991 [9 99999999 ,9 99 9 999 9999999999 9 99 999 9 999999999999l~� 99999999 99 9999 999 99*9'9 ,9999 99499999999 -99949 9999 A 9499 99999)99i4 ,9 9999~ ~ ~ ~ ~ ~ ~~" 9990 o'9 99~~4<4>99999~99> <99999999a99,9 99999 9999~999999999 -<<<~~~ 9999999 9 9~99 999999 9 '927~9' ~ 99999t49 999999~ ~~~~~~~ 99999<99 4 999 99p9 99 9999~~~~~~~~~O 999 "M cl~~~~~~~~~ K51~999 I-. 999 9999 9 99999999,9 99 999999999 ,9999<99 99 99999 1h~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~9'999 wi~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ fol ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~999<9999 5~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~9> W&~~~~~~~~~~~~~~~~99 99 9 99 9 9 99 * 999 99~9 99<999999 ' F A~t~RQ"9<~ 999 9~~j9<'99<99999'~9 9/ 99999 99< 9999 9999 9 9999 999 9 9999Ahad, A ~~~ ~~~ ~~~ ~~~ ~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~99 99 99 ~~999999994 9999 9g F~~~~~~~~~~~~~~~~~~999 9999 9'R9<3'9999999999999 9 op~~~~~~~~~~~~~~~~~~~~~~~~~9~~�'999'99 9 9 9 9999 9990 999L I N , 99 99~9/99999 999999 '949 9 ~ 99j99 999 9994999999 ~~9 9999999H i3 999~99999 9997/994 <999 99<499 99999 ~ 99 99999(99 9~9999999999999999 999 99999999<999999 999 99999 "p,~~~~~~~~~9999 99 99<49 9 999999999 999999/9999W999~999 999999 C) ~ ~ ~ ~~rnfr iue47GnrlzdWtad ta INDI~~~~~~~~~~~~~~> AN RIVER 43 NZ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~3 4"' K.- A~~~ M,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 W~~~~~~~~~~~~~~~~~~~~V Bethany Beach Figure 48 Generalized Wetlands Atlas 4~~~~~~~ slNV;A 4~~~~~~~~~~~~~~~~~~~ F~~~~~~~~~~~~~ / V~~~~~R %~~~~~~~~~~~~~~~~~~~~~~~~ '4 ~~~~~~~~~~~~~~~Is ii6 V ME- Selbyvi lieFigure 49 Gneralized Wtlands AJla 4~~~M C~~~~~~~~~~~X) /~~~O $7~~~~~~~~4 5 ______________ #77~~~~-e / MARY~~LA7~D $77777 /~~~~~~~~AswmnByFgr 0GnrlzdWtad ta k ~~~~~~~~~~WETLANDS DRAINAGE AREAS When viewing the wetlands of the State from the air, it becomes apparent that the wetlands are usually associated with river drainage basins, such as the Christina River, St. Jones River and Broadkill River. However, not all wetland areas are associated with large freshwater inputs, e.g., Cedar Creek. Chamberlain (1951) first devised the concept of subdividing Delaware's wetlands for the purpose of description and comparison using the idea of drainage basins. By using this sytem in conjunction with the vegetative zones as determined from aerial photographs, the State can logically be divided into twenty distinct wetland areas. This is of particular use when trying to assess the composition of an area and the comparative attributes of one wetland area as opposed to another (see Figure 51). RESULTS OF MAPPING Once the wetlands have been divided into drainage areas and mapped into zones according to the Classification System, many interesting things can be determined. First, the area of each wetland drainage basin can be measured (Table 2). From this information, the relative percentage makeup of each vegetative zone in a basin can be computed (Table 3). Thus, each wetland drainage area is characterized in terms of overall size and vegetative composition by zone. In addition, the amount of land and relative percentage of wetlands lost or impounded (see Tables 2 and 3) can be determined for each drainage area. This is accomplished by comparing U. S. Department of Agriculture aerial photographs of 1938 (the earliest known to exist) and 1954 with the most up to date aerial photographs of 1973. As an example, the St. Jones River, Drainage Number 11 (Figure 52) has lost 15 per cent of its total wetland area to impounding activities (Area C) since 115 1938. Although impounding an area does not destroy habitat as does construction, it does convert a marsh community into a freshwater community. (see Impounding.) Area B is classified as Zone I, Salt Marsh Cordgrass, Spartina alterniflora. Salt marsh cordgrass composes 87.8 per cent of the St. Jones River Basin as it exists today. Area A is classified as Zone V, Transition Marsh and composes the remainder (12.2 per cent) of the area's wetlands. This zone is a complex one, with a diverse grouping of vegetative species (refer to Wetlands Classification System). The total area of what was formerly marsh in 1938 is the total of all eight zones or 1,360.0 hectares (3,359.2 acres) for the St. Jones River Basin. However, since the area impounded is no longer true marsh, the area of marsh remaining is 1,155.7 hectares (2,854.6 acres). In each drainage basin the total area in 1938 represents a summation of the eight zones which compose the marsh, whereas the total area in 1973 refers to the area of marsh which remains intact today. The total area of marsh for the State of Delaware in 1938 was 37,114.2 hectares (91,672.1 acres). This represents a summation of all of the marsh zones for all of the drainage areas. The total area of marsh for 1973 was 33,773.4 hectares (83,420.3 acres), a summation of Zones I through VI for all the drainage areas. This represents a 9.0 per cent decrease in the total marsh area over a span of thirty-seven years. MARSH LOSS FOR THE STATE OF DELAWARE (1938 to Present) Total Marsh: 1938 37,114.2 hectares (91,672.1 acres) Total Marsh: 1973 33,773.4 hectares (83,420.3 acres) Net Loss: 1938-1973 9.0% Loss to Construction: 1938-1973 4.7%* Loss to Impounding: 1938-1973 4.3% *Does not include construction on areas less than 3.6 hectares (8.9 acres). 116 FIGURE 51 WETLAND DRAINAGE AREAS OF DELAWARE 1. CHRISTINA RIVER -- Includes Churchmans' Marsh to G ~~~2 ~Delaware River. 2. NEW CASTLE to DELAWARE CITY -- Includes seven small marsh areas including Dragon Creek, Beybold Cove, Red Lion Creek and Army Creek. 3. PORT PENN to REEDY POINT -- Includes 1,000 Acre Marsh (St. Georges Creek). V(~~~ ~ ~4. AUGUSTINE CREEK. 5. SILVER RUN. 6. LISTON POINT to APPOQUINIMINK -- Includes Blackbird Creek, Hangmans Run, Appoquinimink River and Drawyers Creek. 7. CEDAR SWAMP. 8. SMYRNA RIVER. 9. LITTLE RIVER to BAKEOVEN POINT -- Includes Little River, Mahon River, Simons River, Leipsic River and Duck Creek. t < s10. KITTS HUMMOCK to PICKERING BEACH. 11. ST. JONES RIVER. 12. MURDERKILL RIVER. ll A 1O 13. BIG STONE BEACH to BENNETTS PIER. 14. CEDAR CREEK and MISPILLION RIVER. 15. SLAUGHTER CREEK and SLAUGHTER NECK DITCH. 16. PRIMEHOOK CREEK. / 13 17. BROADKILL RIVER. 12 18. CAPE HENLOPEN. \ " a19. REHOBOTH, INDIAN RIVER, LITTLE ASSAWOMAN BAYS. 20. NANTICOKE RIVER and BROAD CREEK. A0 117 TABLE 2 Area of Wetlands* Contained in Each Drainage Area Total and Net Flora Classification by Zone in Delaware in Hectares Area of Delaware Total and Net Wetlands in Area of Delaware Hectares Wetlands in Acres Drainage Total Net Total Net Number I II III IV V VI X XI Area Area*** Area Area*** 1 78.0 89.2 427.4 408.8 1,003.4 594.6 2,478.4 1,468.7 2 561.2 289.9 412.5 1,263.6 851.1 3,121.1 2,102.2 3 542.6 315.9 3.7 33.4 895.6 858.5 2,212.1 2,120.5 4 11.1 278.7 289.8 289.8 715.8 715.8 5 349.3 349.3 349.3 862.8 862.8 6 2,058.8 122.6 185.8 680.1 3,047.3 3,047.3 7,526.8 7,526.8 7 895.6 55.7 951.3 951.3 2,349.7 2,349.7 8 107.8 680.1 702.4 1,490.3 1,490.3 3,681.0 3,681.0 9 6,481.1 2,887.5 7.4 52.8 249.0 18.6 1,007.1 10,702.7 9,677.0 26,435.7 23,901.2 10 245.3 89.2 174.7 33.4 100.3 642.9 542.6 1,588.0 1,340.2 11 1,014.5 141.2 204.4 1,360.1 1,155.1 3,359.4 2,853.1 12 955.1 104.1 356.8 37.2 1,453.2 1,416.0 3,589.4 3,497.5 13 334.5 85.5 286.2 163.5 369.7 869.7 2,148.2 2,148.2 14 2,582.8 70.6 304.7 85.5 386.5 14.9 3,445.0 3,430.1 8,509.2 8,472.3 15 44.6 349.3 174.7 48.3 616.9 616.9 1,523.7 1,523.7 16 204.4 386.5 624.3 966.2 2,181.4 2,181.4 5,388.1 5,388.1 17 1,731.8 185.8 78.0 1,995.6 1,917.6 4,929.1 4,736.5 18 698.6 44.6 40.9 137.5 921.6 743.2 2,276.4 1,835.7 19 2,530.8 130.1 776.7 63.1 3,500.7 2,660.9 8,646.7 6,572.4 20 130.1 3.7 133.8 130.1 330.5 321.3 Total Area by 19,896.8 4,831.1 1,077.8 2,768.5 4,351.8 847.4 1,757.8 1,583.0 Zone Percent Take-Up 58.9% 14.3% 3.2% 8.2% 12.9% 2.5% Total & Net Area 37,114.2 33,773.4 91,672.1 83,420.3 * Generalized boundaries, areas may be somewhat less than total official Wetlands Act measurement due to mapping scale. ** 1 hectare = 2.47 acres ***Net Area = Total Area - ('Lost Marsh' + 'Impounded Marsh') TABLE 3 Percent Composition of Wetland Drainage Areas by Vegetative Zones in 1973; Percent of Wetlands Lost to Construction (X) or Impoundment (Xi) since 1938 Percent Lost Drainage Percent of Each Zone Since 1938 Area I II III IV V VI X XI 1 13.1 15.0 71.9 40.7 2 65.9 34.1 31.9 3 63.2 36.8 0.4 3.7 4 3.8 96.2 5 100.0 6 67.6 4.0 6.1 22.3 7 94.0 6.0 8 7.2 45.6 47.1 9 67.0 29.8 0.1 0.5 2.6 0.2 9.4 10 45.2 16.4 32.2 6.2 15.6 11 87.8 12.2 15.0 12 67.4 7.4 25.2 2.6 13 38.5 9.8 32.9 18.8 14 75.3 2.1 8.9 2.5 11.3 0.4 15 7.2 56.6 28.3 7.8 16 9.4 17.7 28.6 44.3 17 90.5 9.7 3.9 18 94.0 6.0 4.4 14.9 19 95.1 4.9 22.2 1.8 20 100.0 2.8 119 ~~~DOVER ~FIGURE 52 DOVER ILLUSTRATION OF VEGETATIVE ZONES ..i: ' WITHIN A DRAINAGE AREA: :#11, ". ~ST. JONES RIVER /:: DEL. RT~~~. 113 .- ......Ema BAY T 113 S, P........ ...... *11 ST JONES RIVER HECTARES ACRES A. ZONE V TRANSITION MARSH 141.2 348.7 B. ZONE I CORDGRASS MARSH 1,014.5 2505.8 C. ZONE X IMPOUNDED MARSH 204.4 504.9 TOTAL AREA 1938 = SUM OF ALL ZONES 1360.1 3359.4 TOTAL AREA 1973= TOTALAREA 1938-(ZONES X+X') 1155.7 2854.6 TOTAL AREA=ZONE X+ X'/TOTAL AREA 1938 15 % 120 j ~~~Construction has contributed to 4.7 per cent of this loss and 4.3 per cent to impounding projects. The estimate of 4.7 per cent for construction is a conservative one, however, since mapping areas of less than ten acres in size was not possible due to the scale and scope of the project. In all probability, the total loss due to construction would approach 6 per cent, thus making the loss of wetlands from 1938 to 1973 approximately 10 per cent. DISCUSSION OF DRAINAGE AREAS The following are short descriptions of the twenty wetland drainage areas of the State as shown in Figure 51. 1. Churchman's Marsh to the Delaware River - This area includes the wetlands along the Christina River to the point where it empties into the Delaware River. Although most of Churchman's Marsh south of Interstate 95 has been taken over by Reed grass, this wetland area still includes fairly large patches of arrow-arum and Pickerel weed along with some cordgrass, wild rice, and cattails. It provides food and shelter for wildlife in an area where much of the original wetland has been lost to highways, housing and industry. 2. Pigeon Point to Delaware City - This area is composed of all the coastal wetlands from the Delaware Memorial Bridge to Delaware City which includes Army Creek, Red Lion Creek, Reybold Cove and Dragon Creek. It also includes Pea Patch Island. In this area there are extensive stands of Reed grass and large patches of arrow-arum and Pickerel weed. Most of it borders closely on the Delaware River. 3. Reedy Point to Port Penn - Included in this area are 1,000 acre marsh (St. Georges Creek), Augustine Wildlife Area and Reedy Island. Except for 1,000 acre marsh, which provides food and shelter for some wildlife, most of this area has been taken over by almost solid stands of Reed grass. 121 4. Augustine Creek - This area includes all the wetlands bordering Augustine Creek and its tributaries. It consists of cordgrass close to the Delaware River and transition marsh inland. It represents a high quality area in terms of muskrat and waterfowl habitat. 5. Silver Run - This area includes all the wetlands associated with Silver Run. Extensive patches of this area have been taken over by Reed grass reducing its value to waterfowl and wildlife in general. 6. Appoquinimink River to wetlands near Liston Point - This area includes Drawyers Creek, Appoquinimink River, Hangman's Run and Blackbird Creek and has been treated as one area because all of the rivers and creeks come together in one almost continuous marsh bordering on the Delaware River. It consists of extensive cordgrass marsh, transition marsh and some salt meadow and provides valuable food and shelter for geese, ducks, muskrats and other wildlife. 7. Cedar Swamp - All of the wetlands north and west of Collins Beach that are associated with Cedar Swamp are included in this drainage area. This wetland area is not connected with any major river but forms an extensive network of creeks bordered with salt marsh cordgrass and considerable stands of ')g cordgrass. Reed grass is present In relatively small patches. The presence of frequent hunting blinds would indicate considerable use by waterfowl. 8. Smyrna River - This area includes wetlands from Delaware Point south to the mouth of the Smyrna River and inland to include not only the Smyrna River, but also Corks Point Ditch and Sawmill Branch. The wetlands along the Smyrna River form a patchwork of salt meadow marsh interspersed with cordgrass and big cordgrass. It is gradually becoming transition marsh inland with patches of wild rice. This entire area is valuable in terms of wildlife, especially muskrats, ducks and geese. 9. Little River to Bakeoven Point - This large area represents a wide 122 and continuous stretch of coastal wetlands that includes the Woodland Beach Wildlife Area, Bombay Hook Migratory Waterfowl Refuge, the Leipsic River, Green Creek, Simons River, Mahon River and the Little River. It consists of extensive areas of cordgrass and salt meadow which provide a major refuge for ducks, geese and other wildlife. Some of the state's best hunting is found in the Little Creek area. 10. Kitts Hummock to Pickering Beach - This is a narrow, somewhat drier wetland area with few creeks and only scattered areas suitable for waterfowl. It includes a large impounded area south of Kitts Hummock and a cordgrass marsh in the vicinity of Pickering Beach. 11. St. Jones River - This area includes all of the wetlands associated with the St. Jones River from Bower's Beach inland to Dover. This area contains large areas of cordgrass and is a valuable area for wildlife, especially ducks and geese. 12. Murderkill River - This area includes the wetlands along the Murderkill River and its tributaries from South Bowers inland and beyond Frederica. Cordgrass marsh, salt meadow and transition marsh are all found in large portions of this area. Habitat for ducks, geese and other wildlife is of good quality. 13. Big Stone Beach to Bennett's Pier - This is a narrow wetland area with no major drainage except to the north of Bennett's Pier which consists of a large cordgrass marsh. South of Bennett's Pier the area consists of a shrubby wetland containing numerous ponds attractive to waterfowl and a fairly large area of Reed grass. 14. Cedar Creek and Mispillion River - This area includes wetlands from Slaughter Beach north to just below Big Stone Beach including Cedar Creek, the Mispillion River, Crooked Gut and Grecos Canal. This large area of marsh is primarily cordgrass, all extensively ditched for mosquitoes and used moderately 123 by waterfowl. 15. Slaughter Creek and Slaughter Neck Beach - Included in this area are wetlands from Shorts Beach to just south of Slaughter Beach. This is a fairly narrow stretch of coastal wetland primarily salt meadow bounded along the bay by Reed grass and inland by transition marsh. 16. Primehook Creek - This drainage area includes Broadkill Beach north to Shorts' Beach and inland along Primehook Creek. This wetland area includes large sections of transition marsh and many ponds. Most of it is part of the Primehook National Wildlife Refuge and its value to wildlife, especially ducks and geese is excellent. 17. Broadkill River - This area extends from Roosevelt Inlet north to Broadkill Beach including Canary Creek, Red Mill Creek and the Broadkill River. Part of this area belongs to the Primehook National Wildlife Refuge and much of the area consists of large stretches of cordgrass marsh. 18. Cape Henlopen - This area consists of cordgrass marsh along the Lewes- Rehoboth Canal between Lewes and Rehoboth and includes Gordon's Pond, which is an excellent area for ducks. 19. Rehoboth Bay, Indian River Bay and Little Assawoman Bay - This area consists of all the wetlands around these three bays including the various streams that flow into them. Most of it is fringe marsh, primarily cordgrass. 20. Nanticoke River - All the wetlands along the Nanticoke River to Seaford and Concord and along Broad Creek to Laurel are included in this drainage area. These are intermittant fringe wetlands that are almost entirely arrow-arum- Pickerel weed. Some cattails, wild rice and other transition zone vegetation occur along the landward margins. 124 DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 1 - Christina River Total Wetland Area 595 Hectares 1,470 Acres Composition: Zone I (Cordgrass): 0 ha Zone V (Transition): 89 ha (15%) Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 427 ha (72%) WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 409 ha VALUES Zone IV (Reed grass): 78 ha (13%) Marsh Impounded: 0 ha 1. Recreational value Tremendous fishing potential. Unique area of aesthetic and recreational value (boating, fishing, hiking, along river from Christiana Village to Churchman's Road -- ideal canoe route. clamming, crabbing, bird Some crabbing and perch fishing occurring presently. watching) 2. Value as a wildlife Some rabbit, muskrat, raccoon, oppossum, deer. habitat (muskrats, otters, crabs, etc.) 3. Value as an avian Used by snowy egrets, Canada geese, black ducks, ruddy ducks, and wood ducks, habitat (shore birds, especially in Churchman's Marsh. Some pheasants and rails can also be found. waterfowl, songbirds) 4. Value as a spawning White perch, walleye, muskies have been taken from area. Anadromous fish also and nursery area (fish, pass through area during migrations. shellfish, invertebrates, etc.) 5. Value as a primary Improving. producer 6. Hunting and trapping Historically one of the ten best waterfowl hunting marshes in the Atlantic Flyway. potential Being so close to Wilmington, the area provides little isolation necessary for successful trapping, so trapping use is low. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER I - Christina River 7. Pest generative Generally, pest production is low. However, in certain disturbed sections of the potential (greenheads, area, some mosquito production can be expected in wet years. Natural undisturbed salt marsh mosquito, areas experience flushing to keep production in these areas low. deer flies) 8. Value as a buffer Some housing nearby which benefits from buffering capacity of marsh. Coastal to floods, washover and/ flooding controlled more by local streams than by marine processes. or as a control to upland erosion 9. Physiographic value Holocene marsh sediments about ten feet thick, compaction minor. (size, tide range, unique geologic features) 10. Degree of human Impounded years ago, not for mosquito control, but for farming. Impounded areas, perturbation to date however, have not been maintained for most of this century. Except for Christiana (construction, impound- to Churchman's Road area, marsh is now altered by 1-95. ing, ditching, etc.) Some archaeological finds in Newport area. Clyde farm area (most productive archaeologi- 11. Historical value. Di tean Del ware), Remains of old pilings and wharfs from 17Q0's can still.he foun~. larlites o peole Mna in area descrlbe t e areat importance o mars to resiaents ol area. 12. Potential for indus- High pressure due to Wilmington, Newport, Newark urban sprawl. Wilmington port trial/commercial/ expansion possible. residential development 13. Value as a sediment Water quality is moderate. Much sediment is also trapped. trap and water quality purifier 14. Other unique or Has important natural and historical area in Christiana Village-Churchman's Road potential characteristics section which is remaining undisturbed piece of historically important marsh of area area. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 2 - New Castle to Delaware City Total Wetland Area 851 Hectares 2,102 Acres Composition: Zone I (Cordgrass): 0 ha Zone V (Transition): 0 ha Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 290 ha (34%) WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 412 ha VALUES Zone IV (Reed grass):561 ha (66%) Marsh Impounded: 0 ha 1. Recreational value High value for bird watching, especially in Dragon Run, Red Lion and Pea Patch Island (boating, fishing, hiking, areas. Crabbing and fishing in ditches that run through Zone IV. Much fishing also clamming, crabbing, bird done in impoundments that are scattered throughout area. watching) 2. Value as a wildlife Deer, muskrat, raccoon, rabbit, oppossum. Deer herds are very healthy. habitat (muskrats, otters, crabs, etc.) Dragon Run Marsh good area for all waterfowl (especially wood duck). Pea Patch Island 3.hVabit (shore abird has breeding and roosting heronry of Qreat importance in which nine species of water birds habitat (shore birds, waterfowl, songbirds) can be found. Area at Mouth of Red Lion good for song birds. Least bittern can be found here -- one of few places in state. 4. Value as a spawning Dragon Run fishing good. In southern regions of area, nursery for spot and sea and nursery area (fish, trout are still good. Area used for spawning and nursery for some herring and shellfish, invertebrates, blueback. Good area for white perch and stripers. etc.) Based on the amount of fish and birds associated with area, the primary production is 5 Value as a produery very high. Area is also very interesting because of the great variety of plants that grow there. 6. Hunting and trapping Some trapping in Dragon Run area and in other freshwater sections. Hunting good potential in Reedy Island area with proper techniques. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 2 - New Castle to Delaware City 7. Pest generative potential (greenheads, Generally low. Some mosquito production. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Moderate value. or as a control to upland erosion 9. Physiographic value Marsh forms shoreline edge. Thickness of holocene marsh sediments variable -- (size, tide range, unique 10 feet at Delaware City to 50 feet at Reybold Cove. Coastal plain here is narrow. geologic features) Dragon Run produces water for Getty Oil. 10. Degree of human Dragon Run and Red Lion areas are impounded as are marshes near New Castle. Other perturbation to date areas susceptible to impoundment. Water intake structures of Getty Oil in Reybold (construction, impound- Creek poses problems to fish -- many get caught on screens of intake pumps. ing, ditching, etc.) Many marsh areas diked by Swedes for agriculture purposes. Natural vegetation of area was probably mostly wild rice which attracted many birds, especially the bobolink. 12. Potential for indus- trial/commercial/ High pressure because of presence of Getty Oil. residential development 13. Value as a sediment Dragon Run and Red Lion water quality fair to good. Water quality fair to good at trap and water quality Pea Patch. Area generally of value as sediment trap as witnessed by thick sediment purifier beds in many sections. 14. Other unique or Dragon Run area, northernmost intact ecological unit along Delaware River. Educational potential characteristics value (Gunning Bedford school in area). Purple Gallinule nesting in 1975 -- probably of area northernmost record. Trailing arbutus on adjacent upland area. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 3 - Port Penn to Reedy Point Total Wetland Area 859 Hectares 2,122 Acres Composition: Zone I (Cordgrass): 0 ha Zone V (Transition): 316 ha (37%) Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 4 ha VALUES Zone IV (Reed grass):543 ha (63%) Marsh Impounded: 33 ha 1. Recreational value High value for all recreational uses. Bird watching excellent in 1000 Acre Marsh. (boating, fishing, hiking, Crabbing, fishing in Zone V especially. clamming, crabbing, bird watching) 2. Value as a wildlife habitat (muskrats, otters, 1000 Acre Marsh -- good area for muskrat, otter, mink -- historically, the best crabs, etc.) area in the state. High populations of snapping turtles. 1000 Acre Marsh--high quality for song birds and waterfowl (geese, mallards, teals, black 3. Value as an avian and pintail). Blue-winged teal produce many young here. Broods also produced by mallard, habitat (shore birds, black and gadwall. Good area for rusty blackbird (rare in Delaware). Large blackbird waterfowl, songbirds)rosinfladspng roost in fall and spring. 4. Value as a spawning 1000 Acre Marsh: Predominant fish--carp, eels. River and Canal: One of the best spawning and nursery area (fish, areas for stripers, white perch, yellow perch, herrings. Nursery area for stripers, shellfish, invertebrates, white perch, spot, sea trout, menhaden, herrings, anchovies. etc.) 5. Value as a primary 1000 Acre Marsh -- moderate value, primarily from road (Route 9) to Bay. producer 6. Hunting and trapping 1000 Acre Marsh -- high trapping value. High potential for hunting of geese, mallards, potential ducks, green-winged teals. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 3 - Port Penn to Reedy Point 7. Pest generative potential (greenheads, Flies and mosquito present no problem. Some deer flies on "hot" days. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Size enhances value as storm surge buffer, primarily in area from highway to or as a control to upland river. erosion 9. Physiographic value (size, tide range, unique Broad marsh-holocene muds less than 30 feet thick with moderate compaction. geologic features) 10. Degree of human perturbation to date Not much of area is ditched although there is a major impoundment in area for (construction, impound- water level and vegetation control. Other small impoundments north of Port Penn. ing, ditching, etc.) Marshes impounded and water pumped by windmills until turn of century. Sturgeon and shad 11. Historical value. fleet center in 1880's to 1900. Local museum in Port Penn details history of area. 12. Potential for indus- Shorefront in public ownership. West end of 1000 Acre Marsh adjacent to Union trial/commerciall Carbide holdings, so pressure to develop is present. residential development 13. Value as a sediment 1000 Acre Marsh -- relatively good water quality. C & D Canal water quality good. trap and water quality Important sediment trap. purifier 14. Other unique or 1000 Acre Marsh has natural area status. Bigg's farm--fossiliferous outcrop on potential characteristics C & D Canal. Tributary of Scott's Run almost unaltered so important for research of area value. Rusty blackbirds here -- rare in State. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 4 - Auqustine Creek Total Wetland Area 290 Hectares 716 Acres Composition: Zone I (Cordgrass): 11 ha (4%) Zone V (Transition): 279 ha (96%) Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass): 0 ha Marsh Impounded: 0 ha 1. Recreational value Good crabbing. High value for carp, catfish, eel and perch fishing. Good (boating, fishing, hiking, bird watching area. High use for bayshore fishing. Future site of major recreational clamming, crabbing., bird park to be developed by State. watching) 2. Value as a wildlife High value for muskrats. Good also for raccoons and deer. Deer herds are very habitat (muskrats, otters, healthy. crabs, etc.) 3. Value as an avian Great Blue Heron rookery (over 100 nests) on upland contiguous to marsh. Relatively habitat (shore birds, high quality area for waterfowl (black ducks, mallards, pintails, green-winged waterfowl, songbirds) teals, Canada geese). 4. Value as a spawning and nursery area (fish, Similar characteristics to Drainage Area Number 3. Top quality area for fish. shellfish, invertebrates, etc.) 5. Value as a primary Moderately productive. producer 6. Hunting and trapping High quality hunting and good trapping now fully exploited. Plans to increase potential hunting use through proper management and control. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAnE AREA NUMBER 4 - Augustine Creek 7. Pest generative potential (greenheads, Biting flies can be bothersome. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Some value. or as a control to upland erosion 9. Physiographic value Marsh forms the shoreline. Holocene muds immediately west of Augustine Beach (size, tide range, unique near Port Penn reach 80 feet in thickness. geologic features) 10. Degree of human perturbation to date (construction, impound- Area has been impounded but undisturbed in other respects. Still unditched. ing, ditching, etc.) Impounded historically. Area named after Augustine Herman who owned much land from this 11. Historical value, area to Maryland border. Local association exists to preserve area. 12. Potential for indus- Low, but houses beginning to be built around fringes. Move underway to place trial/commercial/ land in public ownership. residential development 13. Value as a sediment trap and water quality Water quality is excellent. Good sediment trap. purifier 14. Other unique or Natural area status. Heronry present that is unique, one of largest on east coast. potential characteristics High degree of civic interest in preservation of area. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 5 - Silver Run Total Wetland Area 349 Hectares 862 Acres Composition: Zone I (Cordgrass): 0 ha Zone V (Transition): 0 ha Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass):349 ha (100%) Marsh Impounded: 0 ha 1. Recreational value High recreational potential. Good to excellent crabbing and fishing. Bird (boating, fishing, hiking, watching good especially along Route 9. Green's Beach area good area for clamming, crabbing, bird striped bass fishing. watching) 2. Value as a wildlife habitat (muskrats, otters, High for all types. Excellent muskrat area. crabs, etc.) 3. Value as an avian habitat (shore birds, Moderate. waterfowl, songbirds) 4. Value as a spawning and nursery area (fish, Important breeding and nursery area for a variety of fish (white perch, rock, shellfish, invertebrates, eels, carp, yellow perch and blue crabs). etc.) 5. Value as a primary High as witnessed by fish and birds it supports. producer DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAsE AREA NUMBER 5 - Silver Run 7. Pest generative potential (greenheads, Flies present a problem. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and! Surrounding land is mostly farm land which needs moderate protection. or as a control to upland erosion 9. Physiographic value (size, tide range, unique Deep hole at mouth of Silver Run Creek which attracts fish. geologic features) 10. Degree of human perturbation to date Relatively unaltered. Unimpounded, unditched and undeveloped. Much of area in (construction, impound- public ownership. ing, ditching, etc.) 11. Historical value. Little data. 12. Potential for indus- Has been considered for marina development in a State project associated with the trial/commercial/ Augustine Beach project. Other development potential low. residential development 13. Value as a sediment trap and water quality High value for both. Good flushing in area. purifier 14. Other unique or potential characteristics Natural area status. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 6 - Liston Point to Appocuinimink Total Wetland Area 3,047 Hectares 7,526 Acres Composition: Zone I (Cordgrass): 2,059 ha (66%) Zone V (Transition): 680 ha (22%) Zone II (Salt hay): 123 ha (4%) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass): 185 ha (6%) Marsh Impounded: 0 ha 1. Recreational value High recreational value for boating, crabbing, fishing and bird watching. Many (boating, fishing, hiking, scenic overviews in area. Potential for increase in use with relatively little clanninq, crabbing, bird development. watching) 2. Value as a wildlife habitat (muskrats, otters, High quality area for muskrats, deer and raccoons. Otters also present. crabs, etc.) 3. Value as an avian High quality area for waterfowl, raptors. Good geese and shorebird populations. habitat (shore birds, Possible eagle nest along Blackbird Creek (but disrupted by DPL power lines). waterfowl, songbirds) 4. Value as a spawning High quality nursery area for white catfish, channel catfish, spot, sea trout, and nursery area (fish, herring with white perch, yellow perch, carp, eels and catfish commonly caught. shellfish, invertebrates, Spawning of herring, yellow perch, white perch. etc.) 5. Value as a primary High quality. producer 6. Hunting and trapping High quality for trapping and hunting, especially in Zones I and V. Estimated that potential 12,000 muskrat pelts could be harvested from area annually. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 6 - Liston Point to Appoquinimink 7. Pest generative potential (greenheads, Moderate to high. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Buffer for farm lands. or as a control to upland erosion 9. Physiographic value Large undisturbed size is dominant factor. Exceptionally deep pre-holocene valleys filled (size, tide range, unique with over 120 feet of holocene mud. Compaction great. Marsh shoreline eroding. Marsh geologic features) drained by both Appoquinimink and Blackbird Creek. 10. Degree of human pDegrturbati to hmat Relatively undisturbed. Not ditched. Major intact ecological unit in northern (consturbtion, impounda Delaware. Some agriculture around edges. ing, ditching, etc.) Contains Hill Island archaeological site. Area where marsh supported economy of 11. Historical value, omnte. communities. 12. Potential for indus- Neck between Blackbird Creek and Appoquinimink is planned for industry post-1985 in trial/commercial/ upland sector. (New Castle County District Plan, 1976). residential development 13. Value as a sediment Water quality high and good sediment trap. trap and water quality purifier 14. Other unique or Natural area of regional significance because of size and unaltered condition. potential characteristics Records of eagle nesting for 60-80 years. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 7 - Cedar Swamp Total Wetland Area 951 Hectares 2,349 Acres Composition: Zone I (Cordgrass): 896 ha (94%) Zone V (Transition): 0 ha Zone II (Salt hay): 55 ha (6%) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass): 0 ha Marsh Impounded: 0 ha 1. Recreational value Excellent bird watching via boat. Crabbing and fishing good. High potential (boating, fisking, for increased recreational use. clammninq, crabbing, bird watching) 2. Value as a wildlife habitat (muskrats, otters, Muskrat, raccoon and deer abundant. crabs, etc.) 3. Value as an avian habitat (shore birds, High quality for waterfowl, raptors and shorebirds. waterfowl, songbirds) 4. Value as a spawning Little data here. Presumably not a spawning area but good nursery area for and nursery area (fish, white and channel catfish, spot, sea trout and herring, with white perch, yellow perch, shellfish, invertebrates, carp, eels and catfish commonly caught. etc.) 5. Value as a primary High quality. producer 6. Hunting and trapping Popular waterfowl hunting area, although permission must be granted by Shell potential Oil Company which owns most of land. Trapping is also good. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 7 - Cedar Swamp 7. Pest generative potential (greenheads, Flies a problem. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Moderate, as land surrounding area is high in elevation. or as a control to upland erosion i9. Physiographic value Pre-holocene valleys filled in with marsh sediments 60 feet thick. (size. tide range, unique Discontinuous sandy barriers separate marsh from bay. geologic features) 10. Degree of human perturbation to date Little altered -- not ditched. Collins Beach provides small harbor. (construction, impound- ing, ditching, etc.) Completely separate from bay until 1880's when a ~torm breeched the beach. Site of early 11. Historical value. attempt a cross peninsular canal. Report o living white ce ar remaining from former stand of rees. 12. Potential for indus- High potential for development by Shell Oil for petrochemical complex near the trial/commerci al area should the Coastal Zone Act prohibitions be removed. residential development 13. Value as a sediment trap and water quality Water quality is high. High value as sediment trap. purifier 14. Other unique or Shell Oil principal property owner; probably bought area as buffer zone or potential characteristics as possible source of freshwater. Important for its unaltered quality. Designated of area a critical natural area. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER - - Smyrna River Total Wetland Area 1,490 Hectares 3,680 Acres Composition: Zone I (Cordgrass): 108 ha (7%) Zone V (Transition): 702 ha (47%) Zone II (Salt hay): 680 ha (46%) Zone VI (Arrow-Arum): 0 ha WIETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass): 0 ha Marsh Impounded: 0 ha 1. Recreational value High potential for sport fishing and boating. Bird watching and crabbing (boating, fishing, hiking, excellent via boat. Commercial crabbing industry also centered here. clamming, crabbing, bird watching) 2. Value as a wildlife habitat (muskrats, otters, Excellent area for muskrat, raccoon and deer especially in sectors of lower habiat muskats ottrssalinity crabs, etc.) y 3. Value as an avian Good geese area. All waterfowl frequent area,especially teals. Quail and habitat (shore birds, pheasant also present. Loggerhead shrike sited here -- rare bird in state. waterfowl, songbirds) 4. Value as a spawning Good quality -- Spawning of herring, white perch, yellow perch. Nursery area and nursery area (fish, for sea trout, herring, menhaden, stripers. Adults found -- sea trout, white shellfish, invertebrates, catfish, stripers, hogchoker. etc.) 5. Value as a primary Moderate to high. producer 6. Hunting and trapping Heavily hunted area--most heavily hunted in state for geese. Much of hunting done on potential private reserves which run as commercial businesses. Trapping heavy for what area supports. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 8 - Smyrna River 7. Pest generative potential (greenheads, Greenhead flies abundant. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Some value as a buffer. or as a control to upland erosion 9. Physiographic value (size, tide range, unique geologic features) CD 10. Degree of human Unditched marsh. Creek formerly was dredged but dredging is now done only very perturbation to date infrequently. Many small impoundments throughout area for geese. Head water (construction, impound- impounded. ing, ditching, etc.) Oyster beds have been historically jmportant but have experienceg umblems.recently. 11. Historical value. River formerly went to Lelpsic until prerevotuntlonary caha was uilt. rick StorT Landina -- steamboat landina Drior to 1840. 12. Potential for indus- Shell Oil owns area down to Creek on north side. The State owns land to south trial/commercial/ of Creek roqidPntial dPvPlnnmont o 13. Value as a sediment trap and water quality High both as purifier and sediment trapper. purifier 14. Other unique or Heart of goose population. Corn and soybean farming area of importance both potential characteristics in agricultural sense and in attracting geese. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 9 - Bakeoven Point to Pickerina Beach Total Wetland Area 9,677 Hectares 23,902 Acres Composition: Zone I (Cordgrass): 6,481 ha (67%) Zone V (Transition): 249 ha (3%) Zone II (Salt hay): 2,878 ha (30%) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 7 ha Marsh lost since 1938: 19 ha VALUES Zone IV (Reed grass): 53 ha (1%) Marsh Impounded: 1,007 ha 1. Recreational value (boerationg, fishing, hikinExcellent for bird, wildlife watching; nature walks. Crabbing excellent; sport (boating, fishing, hiking, fishing is good. Bay finfishing and surfcasting excellent. Valuable area for cwatincrabbing,)bir commercial crabbing. watchi ng) 2. Value as a wildlife Whitetail deer, muskrats, otters, pheasant, bobwhite, cottontail all abundant. habitat (muskrats, otters, Peak area for whitetails. crabs, etc.) 3. Value as an avian Top quality for migratory shorebirds and waterfowl as Canada geese, snow geese, habitat (shore birds, whistling swans, 17 species of ducks (mallards, black, green-winged teals). Brood area waterfowl, songbirds) for gadwalls, wood ducks, black ducks. Blue herons, cattle egrets, cormorants use area. Rails prominent. Resident bald eagles (successfully nesting this year). 4. Value as a spawning Carp, bullheads, in impoundments attract birds. Good quality although little and nursery area (fish, specific data. Spawning area for yellow perch, white perch. Adults found include shellfish, invertebrates, sea trout, spot, stripers, white perch. etc.) 5. Value as a primary Excellent due to large areas of cordgrass. producer 6. Hunting and trapping Controlled for management purposes (Bombay Hook). Little River area for hunting potential (waterfowl) one of the best in state. Trapping is excellent. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 9 - Bakeoven Point to Pickering Beach 7' Pest generativei 7 Pest generative Large areas of impounded marsh have cut down breeding of salt marsh mosquito (Aedes potential (greenheads, sollicitans). However, breeding of freshwater mosquitos(Culex salinarius, Anophales salt marsh mosquito, bradleyi and Uranotaenia sapphirina increased after impounding. Greenhead flies abundant. deer flies) 8. Value as a buffer to floods, washover and/ High quality against flood from bay due to extensive cordgrass. or as a control to upland erosion 9. Physiographic value The size and relatively undisturbed, manaqed condition makes the area of hiqhest auality. (size, tide range, unique Broad Marsh underlain by 20-80 feet of holocene muds. Area, especially Port Mahon, geologic features) undergoing rapid erosion. Open ponds in marsh common. 10. Degree of human Great deal of management and consequently impounding. Ditched in northern section perturbation to date but not in south. Outer marshes -- Kelly, Kent, Bombay Hook Islands very primitive. (construction, impound- However, high noise level from airplanes, helicopters. ing, ditching, etc.) Railroad line and old road to WoodTDd Beac Woodland,,Beach form6rly freshwater but has 11. Historical value. been reverting to sa ltwater since 18's. taylors ut , ook by ud ey Lunt, about area. 12. Potential for indus- Probably low. trial/commercial/ residential development 13. Value as a sediment High quality as sediment trap and water quality purifier due to extensive areas trap and water quality of cordgrass. purifier 14. Other unique or Largest block of marsh in Delaware. Mudflats and associated marshes of Woodland potential characteristics Beach. Bombay Hook Island, Kent Island, Kelly Island -- natural areas. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 10 - Pickering Beach to Kitts Hummock Total Wetland Area 543 Hectares 1,341 Acres Composition: Zone I (Cordqrass): 245 ha (45%) Zone V (Transition): 0 ha Zone II (Salt hay): 89 ha (16%) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 175 ha (32%) Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass): 33 ha (6%) Marsh Impounded: 100 ha 1. Recreational value (boating, fishing, hiking, Bay fishing and surf casting in the area. Net fishing popular. clamming, crabbing, bird watching) 2. Value as a wildlife Extensive populations of all mammals especially deer, raccoon, oppossum, muskrat, habitatkrats, otet otter, rabbit -- essentially same value and use as Area Number 9. crabs, etc.) 3. Value as an avian Abundant geese and dabbling ducks. Impoundments harbor very high population of over- habitat (shore birds, wintering fowl. Short billed marsh wrens frequently spotted. Annual large congregations waterfowl, songbirds) of sandpipers and plovers occasionally in summer--attracted by spawning horseshoe crabs. 4. Value as a spawning and Vlurser area (fispn Little specific data -- extensive oyster beds offshore which are critical and nursery area (fish, toyseinur. shellfish, invertebrates, etc.) 5. Value as a primary producer producer ~~~Very good. 6. Hunting and trapping Very high. Prime goose and duck hunting areas. potential DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 10 - Pickerinq Beach to Kitts Hummock 7. Pest generative potential (greenheads, Greenheads numerous. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Valuable buffer to farms. or as a control to upland erosion 9. Physiographic value (size, tide range, unique Moderate compaction, holocene muds 30 feet thick. geologic features) 10. Degree of human perturbation to date Except for ditching, very little perturbation. (construction, impound- ing, ditching, etc.) 11. Historical value Area in which oysters were first planted in State--around 1840. Oyster regulations developed over these attempts. Caesar Rodney farm nearby. 12. Potential for indus- trial/cormmercial/ Probably not high. residential development 13. Value as a sediment trap and water quality purifier 14. Other unique or potential characteristics of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 11 - St. Jones River Total Wetland Area 1,155 Hectares 2,853 Acres Composition: Zone I (Cordgrass):1,015 ha (88%) Zone V (Transition):141 ha (12%) Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass): 0 ha Marsh Impounded: 204 ha 1. Recreational value (boating, fishing, hiking, Party boats, fishing, launching ramps, shellfishing. Excellent bird watching via boat. clamming, crabbing, bird Crabbing excellent and heavily pursued. watching) 2. Value as a wildlife habitat (muskrats, otters, High numbers of oyster spats, however, few adults. Fur bearers abundant in crabs, etc.) upper reaches. Deer, pheasant raccoons, rabbit. 3. Value as an avian habitat (shore birds, Relatively good area for waterfowl, shore birds and song birds. waterfowl, songbirds) 4. Value as a spawning Most brackish water resident species of Delaware can be found here. Migratory l and nursery area (fish, marine species common at mouth. shellfish, invertebrates, etc.) 5. Value as a primary Relatively high due to extensive cordgrass. producer 6. Hunting and trapping potential High for hunting. Excellent use and potential. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 11 - St. Jones River 7. Pest generative potential (greenheads, Greenhead heaven. Situation critical during tourist season. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Yes. or as a control to upland erosion 9. Physiographic value (size, tide range, unique Some impoundments. Abundant ponds on marsh. geologic features) 10. Degree of human Good deal of perturbation due to proximity of Dover and associated urban perturbation to date developments. Ditched. Sand has blown into marsh because of beach (construction, impound- nourishment programs. ing, ditching, etc.) First settlements adjacent to marsh "Towne Point". River course modified to accommodate 11. Historical value. stemboats Johns Neck--intact piece of land from William Penn era. Land held privately until T1960s, now belongs to Delaware Widlands. John lckinson nouse nere. 12. Potential for indus- Pressure for development probably high. Presence of Delaware Wildlands does, trial/commercial/ however, provide support for preservation. residential development 13. Value as a sediment trap and water quality Good qualities for both due to extensive cordgrass. purifier 14. Other unique or potential characteristics of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 12 - Murderkill River Total Wetland Area 1,416 Hectares 3,498 Acres Composition: Zone I (Cordgrass): 955 ha (67%) Zone V (Transition): 357 ha (25%) Zone II (Salt hay): 104 ha (7%) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass): 0 ha Marsh Impounded: 37 ha 1. Recreational value (boating, fishing, hiking, Party boats, launching ramps. Center for Bay fishing. Oyster beds abundant. Crabbing clamming, crabbing, bird excellent. Clamming marginal because of pollution. Bird watching excellent via boat. watching) 2. Value as a wildlife Low level impoundment here attracts predatory wildlife -- otter, muskrat, oppossum, habitat (muskrats, otters deer, rabbit plentiful. crabs, etc.) 3. Value as an avian Abundant ducks. Low level impoundment attracts waterfowl and songbirds. High habitat (shore birds, waterfowl, songbirds) 4. Value as a spawning and nursery area (fish, High numbers of oyster spats and adults. Similar in characteristics to St. Jones shellfish, invertebrates, River. etc.) 5. Value as a primary Relatively high. producer 6. Hunting and trapping Excellent and highly utilized for both. potential DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 12 - Murderkill River 7. Pest generative potential (greenheads, Greenheads present moderate problem. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ High value as buffer zone. or as a control to upland erosion 9. Physiographic value (size, tide range, unique Paleogeography has been studied by Kraft. geologic features) co 10. Degree of human pertubatin todateDitched. Creek dredged for oysters for many years. Some impoundments for (costurbation, impounda University of Delaware research. Sewage from Kent County sewage treatment plant also (construction, impound-afetar. ing, ditching, etc.) Island Field Prehistoric Indian burial ground. National Register status with associated 11. Historical value, ponds and wetlands to west and south Natural Areas status. 12. Potential for indus- High, due to natural deep channel near shore at Big Stone Beach. trial/commercial/ residential development 13. Value as a sediment trap and water quality Good -- due to extensive cordgrass areas. purifier 14. Other unique or potential characteristics Some research. Frederica and area to west has Natural Areas status. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 13 - Big Stone Beach to Bennetts Pier Total Wetland Area 870 Hectares 2,149 Acres Composition: Zone I (Cordgrass): 335 ha (39%) Zone V (Transition): 0 ha Zone II (Salt hay): 86 ha (10%0) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 286 ha (33%) Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass):163 ha (18%) Marsh Impounded: 0 ha 1. Recreational value (boating, fishing, hiking, Bay fishing, surfcasting. Haul seining. clamming, crabbing, bird watching) 2. Value as a wildlife habitat (muskrats, otters, Milford Neck Wildlife Area -- most mammals mentioned previously abundant. crabs, etc.) 3. Value as an avian Excellent for black ducks, teals, mallards and geese. High shore bird habitat (shore birds, utilization. waterfowl, songbirds) 4. Value as a spawning and nursery area (fish, Little data available. shellfish, invertebrates, etc.) 5. Value as a primary Moderate to high. producer 6. Hunting and trapping High; excellent. potential DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 13 - Big Stone Beach to Bennetts Pier 7. Pest generative potential (greenheads, salt marsh mosquito, High. deer flies) 8. Value as a buffer to floods, washover and/ or as a control to upland erosion 9. Physiographic value (size, tide range, unique geologic features) 10. Degree of human pDegrturbati to hmat Fairly low. Ditched. Owned by a consortium of oil companies. perturbation to date (construction, impound- ing, ditching, etc.) 11. Historical value. Used by Delaware Indians. 12. Potential for indus- Pressure to develop area for tank farms, industrial developments because of trial/commercial/ presence of oil companies residential development 13. Value as a sediment trap and water quality purifier 14. Other unique or potential characteristics Indian artifacts. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 14 - Cedar Creek and Misnillion River Total Wetland Area 3J0 Hectares 8,472 Acres Composition: Zone I (Cordgrass): 2,583 ha (75%) Zone V (Transition): 387 ha (11%) Zone II (Salt hay): 70 ha (2%) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 305 ha (9%) Marsh lost since 1938: 15 ha VALUES Zone IV (Reed grass): 85 ha (2%) Marsh Impounded: 0 ha 1. Recreational value (boating, fishing, hiking, Public launching ramps, party boats. Fishing excellent. Bird watching via clammcing ng, bird boat or jetties. Best in State for shorebirds. watching) 2. Value as a wildlife habitat (muskrats, otters, Wide variety. Good populations for all mammals. Similar to area Number 9. crabs, etc.) 3. Value as an avian Good for puddle ducks and sea ducks offshore. Excellent shorebird area. Large habitat (shore birds, habitate w (shorbirds, congregation of Ruddy turnstones during crab breeding seasons. waterfowl, songbirds) 4. Value as a spawning Moderate value. Spawning of resident species only. Marine migrants inhabit and nursery area (fish, during summer. Oyster reefs in rivers. shellfish, invertebrates, etc.) 5. Value as a primary producer producer ~~~High quality as primary producer. 6. Hunting and trapping Excellent hunting. Trapping good, especially in upper reaches of streams -- potential although muskrat has been better in past. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 14 - Cedar Creek and MisDillion River 7. Pest generative potential (greenheads, Data not available. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Yes. or as a control to upland erosion 9. Physioqraphic value (size, tide range, unique Data not available. geologic features) 10. Degree of human Ditched; Mispillion River dredged. Very heavy use of launching facilities. Much perturbation to date of area lost to highway relocation in Milford area. Also high degree of pollution (construction, impound- from Milford in past. ing, ditching, etc.) 11. Historical value. Major archaeological sites (Millman). Shipbuilding area. 12. Potential for indus- trial/commercial/ residential development 13. Value as a sediment Present water quality good. High quality sediment trap and purifier due to trap and water quality extensive cordgrass. Cedar Creek has had some water quality problems recently purifier but source has not been determined. 14. Other unique or Marsh research study area since 1935 (Bourn and Cottam, etc.). Natural Area status. potential characteristics Millman site. Pitcher plant and White Cedar found here. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 15 - Slauahter Creek and Slauahter Neck Ditch Total Wetland Area 617 Hectares 1t524 Acres Composition: Zone I (Cordgrass): 45 ha (7%) Zone V (Transition): 0 ha Zone II (Salt hay): 349 ha (57%) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 175 ha (28%) Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass): 48 ha (8%) Marsh Impounded: 0 ha 1. Recreational value (boating, fishing, hiking, Surf and bay fishing. Bird watching excellent along shoreline. clamming, crabbing, bird watching) 2. Value as a wildlife habitat (muskrats, otters, High value -- mammals are abundant and varied. crabs, etc.) 3. Value as an avian High value -- wide variety especially in winter. Short eared owls present , habitat (shore birds, primarily during migrations. waterfowl, songbirds) 4. Value as a spawning and nursery area (fish, Fish, shellfish, invertebrates also present in area. shellfish, invertebrates, etc.) 5. Value as a primary Moderate. producer 6. Hunting and trapping Good potential. potential DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 15 - Slaughter Creek and Slaughter Neck Ditch 7. Pest generative potential (greenheads, salt marsh mosquito, High. deer flies) 8. Value as a buffer to floods, washover and/ High value because of surrounding farm land. or as a control to upland erosion 9. Physiographic value (size, tide range, unique Relatively narrow marsh. geologic features) 10. Degree of human Not ditched. Potential for herbicides and pesticides from adjacent farm lands perturbation to date to get into system. Lot of boat traffic in lower reaches of Creek. State boat (construction, impound- launching site. Small cannery also in area. ing, ditching, etc.) 11. Historical value. Used by Delaware's Indian populations. 12. Potential for indus- Low. Part of Federal Wildlife Area. trial/commercial/ residential develooment 13. Value as a sediment trap and water quality Data not available. purifier 14. Other unique or 14p Other untiqu characr Much of area is wildlife refuge. Indian artifacts present. potential characteristics of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 16 - Primehook Creek Total Wetland Area 2,181 Hectares 5,387 Acres Composition: Zone I (Cordqrass): 204 ha (9%) Zone V (Transition): 967 ha (44%) Zone I! (Salt hay): 386 ha (18%) Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 0 ha VALUES Zone IV (Reed grass):624 ha (29,%) Marsh Impounded: 0 ha 1. Recreational value (boating, fishing, hiking, Good nature watching area, wildlife and bird watching area. Excellent fishing clamming, crabbing, bird and canoeing. Nature trails throughout area. watching) 2. Value as a wildlife High quality due to Primehook Federal Wildlife Area. Whitetail deer (100). habitat (muskrats, otters, Muskrats (small number). Otters, weasels (low number). Red fox, raccoons: striped crabs, etc.) skunks, oppossums, rabbits all common. Good crabbing in tidal channels. 3. Value as an avian Good area for Canada geese, 11 species of ducks (similar to Bombay Hook). Some nesting. habitat (shore birds, Production of 720 (1974) young black ducks and blue-winged teals) 17 species of waterfowl, songbirds) shorebirds use area. Few species year round inhabitants. Mourning doves, quail, few pheasants. Good area for raptors (hawks and owls). Some osprev. Henlow's soarrows. black rails, short-billed marsh wrens. 4. Value as a spawning and nursery area (fish, Good quality for yellow perch, pickerel, crappies, large mouth bass (all non-tidal). shellfish, invertebrates, etc.) 5. Value as a primary producer 6. Hunting and trapping potential Good area but close to peak use for both with present access and facilities. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 16 - Primehook Creek 7. Pest generative potential (greenheads, Not as much a problem as other areas. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Valueable as buffer zone. or as a control to upland erosi on 9. Physiographic value (size, tide range, unique geologic features) 10. Degree of human Area is largely managed (along creek from Route 14 to Ford's Landing, less so). Some perturbation to date ditching and impounding in past. Roads built into area for fishing in ponds. Former (construction, impound- CCC camp constructed here. Area is returning to natural state. ing, ditchinq, etc.) 11. Historical value. Indian encampments. 12. Potential for indus- trial/commercial/ residential development 13. Value as a sediment trap and water quality purifier 14. Other unique or Has ospreys. Natural Area status. Primehook Creek (Route 14 to Ford's Landing good potential characteristics canoe route). Rare birds -- Henslow's sparrows, black rails, short-billed marsh wrens of area attract many people each year. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 17 - Broadkill River Total Wetland Area 1,918 Hectares 4.737 Acres Composition: Zone I (Cordgrass): 1,732 ha (91%) Zone V (Transition): 186 ha (9%) Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 78 ha VALUES Zone IV (Reed grass): 0 ha Marsh Impounded: 0 ha 1. Recreational value (boating, fishing, hiking, Excellent area for boating, fishing, crabbing. Surfcasting off beach. clamming, crabbing, bird watching) -~ 2. Value as a wildlife U1 ~~~~~~~Mammals abundant. habitat (muskrats, otters,. crabs, etc.) 3. Value as an avian Good seasonal populations of all birds. Dune area behind beach has finches habitat (shore birds, (especially Pine Siskin). waterfowl, songbirds) 4. Value as a spawning and nursery area (fish, Oyster community present. Spawning area for residents. Moderate value as nursery shellfish, invertebrates, area for bluefish, spot. Adult trout, flounders, eels, white perch common. etc.) 5. Value as a primary Good producer. producer 6. Hunting and trapping Area hunted intensively. potential DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINARE AREA NUMBER 17 - Broadkill River 7. Pest generative potential (greenheads, Creation of champagne pools have cut down production of salt marsh mosquito salt marsh mosquito, (Aedes sollicitans). deer flies) 8. Value as a buffer to floods, washover and/ or as a control to upland erosion 9. Physiographic value (size, tide range, unique Ditched. Ponds within marsh. geologic features) 10. Degree of human pDegrturbati to hmat Milton area highly altered. Water quality low but improving. Area ditched and (consturbtion, impounda some ponds have been created in marsh. ing, ditching, etc.) 11. Historical value. Ship building area -- principally sailing vessels. 12. Potential for indus- Moderate pressure now, but would increase if proposed deep water port is developed trial/commercial/ in area. residential development 13. Value as a sediment trap and water quality The area is good sediment trap and purifier. purifier 14. Other unique or Site of many University of Delaware marsh investigations for which it has been potential characteristics given Natural Area status. of area DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 18 - Cape HenloDen Total Wetland Area 743 Hectares 1,835 Acres Composition: Zone I (Cordgrass): 699 ha (94%) Zone V (Transition): 0 ha Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 41 ha VALUES Zone IV (Reed grass): 45 ha (6%) Marsh Impounded: 138 ha 1. Recreational value Excellent area for boating, fishing, crabbing. Public launching areas, party (boating, fishing, hiking, boats, marinas. clamming, crabbing, bird watching) 2. Value as a wildlife habitat (muskrats, otters, Mammals around Gordon's Pond. crabs, etc.) 3. Value as an avian Rookery area for common terns, least terns, gulls, grebes and,periodically,black skimmers. habitat (shore birds, Also only breeding area in state of piping plover. Stopover for many migrants waterfowl, songbirds) especially hawks and bluejays. Gordon's Pond good quality for waterfowl. 4. Value as a spawning and naurser area (fispn Moderate value. Similar to Drainage Number 17. and nursery area (fish, shellfish, invertebrates, etc.) 5. Value as a primary Relatively high. producer 6. Hunting and trapping Good hunting. potential DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 18 - Cape Henlopen 7. Pest generative potential (greenheads, Pest control activities undertaken. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Moderate value as buffer. or as a control to upland erosion 9. Physiographic value Lewes Creek marshes, ancient spit tips studied by University of Delaware (size, tide range, unique Geology Department. geologic features) 10. Degree of human perturbation to date Ditched. Affects area and causes some disturbances but marshes still in (construction, impound- relatively good shape. ing, ditching, etc.) High historc val e--fist settlement in State, etc. Prehistoric ?ccupatioton spit tips 11. Historical value. as evidenced by sell middens (ples of shells left by Indians). Former salt works - Gordon's Pnnd area 12. Potential for indus- 12trial/conmercial/ indus- High pressure due to recreational and industrial (oil associated) development residential development potential. 13. Value as a sediment trap and water quality Good value for both but extremely stressed in both cases. purifier 14. Other unique or Lewes Creek marshes, Gordon's Pond area, marshes of Wolfe Glade and Holland Glade-- potential characteristics Natural Area status. National recognition of these -- only such areas in state. of area Designated as critical natural area by Delaware Nature Education Society. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 19 - Rehoboth. Indian River. Little Assawoman Bays Total Wetland Area 2,661 Hectares 6,573 Acres Composition: Zone I (Cordgrass): 2,531 ha (95%) Zone V (Transition): 0 ha Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 0 ha WETLAND Zone III (Salt bush): 130 ha (5%) Marsh lost since 1938: 777 ha VALUES Zone IV (Reed grass): 0 ha Marsh Impounded: 63 ha 1. Recreational value Highest quality recreational area for boating, sailing, fishing, crabbing, (boating, fishing, hiking, clamming, swimming, skiing. State parks for beaching, fishing, surfing, clammiinq, crabbing, bird clammingtcrabbing, bird swimming. Excellent crabbing. watching) 2. Value as a wildlife Highly managed, Little Assawoman Wildlife Area fairly productive for its size. habitat (muskrats, otters, crabs, etc.) 3. Value as an avian High quality area, particularly Assawoman Wildlife Area. Notable birds in Assawoman-- habitat (shore birds, ospreys, mute swans, brants and,occasionally,European teal and European widgeon. Drainage waterfowl, songbirds) area also important for breeding black ducks, mallards, terns (on Gull Island) and winterinc Dopulation of all ducks. 4. Value as a spawning Relatively high quality. Spawning of winter flounder. Nursery, menhaden, bluefish, and nursery area (fish, mullet, spot, sea trout. Adult flounder, sea trout, croakers. shellfish, invertebrates, etc.) 5. Value as a primary producer 6. Hunting and trapping potential Much hunting. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 19 - Rehoboth, Indian River, Little Assawoman Bays 7. Pest generative 7potestia (greenheratv Research at Assawoman Wildlife Area. Generally, pest problem medium. potential (greenheads, salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ High quality washover and flood protection. or as a control to upland erosion 9. Physiographic value (Phsizeogidrangecunique Remnants of false cape. Coastal lagoon systems studied by Geology Department, (size, tide range, uniqueUnvriyoDear. geologc feaures)University of Delaware. geologic features) 10. Degree of human Extremely high degree of manipulation. Loss of 20% of wetlands since 1938. perturbation to date Ditched. Some impounding. (construction, impound- ing, ditching, etc.) 11. Historical value. Thompson's Island archaeological dig. 12. Potential for indus- 12. Potential/conercial! s Relatively high for residential and commercial uses. trial/commercial/ residential development 13. Value as a sediment trap and water quality purifier 14. Other unique or Several spots in area have nesting ospreys. Bald eagles also nest occasionally. Poplar potential characteristics thicket, Blackwater Creek marshes, False Cape -- Natural Areas status. Assawoman of area Wildlife Area -- extremely valuable mammal and bird area. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS DRAINAGE AREA NUMBER 20 - Nanticoke River and Broad Creek Total Wetland Area 130 Hectares 321 Acres Composition: Zone I (Cordgrass): 0 ha Zone V (Transition): 0 ha Zone II (Salt hay): 0 ha Zone VI (Arrow-Arum): 130 ha (100%) WETLAND Zone III (Salt bush): 0 ha Marsh lost since 1938: 4 ha VALUES Zone IV (Reed grass):O ha Marsh Impounded: 0 ha 1. Recreational value Boating, fishing, bird watching, hiking excellent. (boating, fishing, hiking, clamming, crabbing, bird watching) 2. Value as a wildlife habitat (muskrats, otters, Moderate to good for muskrat but no historical trapping of area. crabs, etc.) 3. Value as an avian Excellent for song birds. Eagle nest in area. Ruffed grouse present. Nearby Pocomoke habitat (shore birds, area has Swainson's and Prothonotary warblers and summer tanager -- all rare here. waterfowl, songbirds) 4. Value as a spawning Shad, stripers and other anadromous fish in waterways. Area where drift netting and nursery area (fish, for shad is common. Excellent freshwater fishing. shellfish, invertebrates, etc.) 5. Value as a primary Moderate. producer 6. Hunting and trapping potential Little use thus far. DELAWARE WETLANDS ATLAS SURVEY OF DELAWARE'S WETLAND DRAINAGE AREAS WETLAND VALUES DRAINAGE AREA NUMBER 20 - Nanticoke River and Broad Creek 7. Pest generative potential (greenheads, Relatively low. salt marsh mosquito, deer flies) 8. Value as a buffer to floods, washover and/ Not really applicable here. or as a control to upland erosion 9. Physiographic value (size, tide range, unique Nanticoke Ridge - Pleistocene marine shoreline possibly. geologic features) 10. Degree of human perturbation to date As of yet, relatively undeveloped, but road and summer home development encroaching (construction, impound- on relatively unspoiled area. Leading to loss of natural benefits. ing, ditching, etc.) 11. Historical value. Numerous pre-historic encampment sites of Nanticoke Indians. Shipbuilding at Bethel. 12. Potential for indus- DuPont expansion likely. Also tempting area for other industries because of trial/commercial/ excellent water supply. residential development 13. Value as a sediment trap and water quality purifier Rare box huckleberry on banks of Broad Creek. Nanticoke R. state line to Woodland and potential characteristics Broad Creek below Laurel - Natural Area status. Linked to Pocomoke swamp area which is potential chareacesi northernmost example of a true southern swamp. Stand of wild rice exists. Stream is navigable. WETLANDS DESTRUCTION WETLANDS DESTRUCTION Various activities involving the wetlands, the near shore zones, or the uplands adjacent to the wetlands have the potential for serious, if not irre- pairable damage to these resources. In many cases proper planning and design can avoid or at least lessen the detrimental impacts. Following are discussions of major activities and their impacts on wetland areas: 1. Dredging and Bulkheading 2. Spoil Disposal 3. Impounding 4. Ditching 5. Waste Disposal 6. Residential, Commercial and Industrial Development 7. Marinas 8. Agriculture For each of the discussed activities, recommendations as to approaches to avoid or reduce adverse impacts are included. It should be emphasized that these recommendations are solely those of the authors and are not necessarily supported by the Delaware State Planning Office, the Coastal Zone Management Program, or the University of Delaware. Also included with each discussion are representative photographs of the activity being described and a list of additional references should more definitive discussions be desired. DREP(HING AND BULKHEADIN( Definition and Description Dredging is the physical act of removing land or bottom material. It is performed to create and maintain channels; to obtain fluvial deposits of sand, gravel and shells for construction materials; to establish marinas; to establish boatyards; and is carried out in conjunction with the creation of waterfront houses or trailers on canals or lagoons (Metzgar, 1973). 165 In many cases, dredging is performed as a navigational aid to maintain access to factories, storage facilities and seafood processing houses, as well as for the passage of pleasure boats. However, dredging marsh to create canals for waterfront dwellings represents a use of dredging that is increasingly popular and profitable. There are two basic modes of dredging, mechanical and hydraulic (Clark, 1974). Mechanical methods include removal by dragline or "bucket and scow". dipper dredge and ladder dredge. The first method, dredging by dragline, employs a crane and large metal bucket to remove sediment from an existing channel or canal. The spoil is either dumped overboard or is placed in a barge and towed to a disposal area. The second type of mechanical dredge, the dipper dredge, consists of a large power shovel mounted on a barge. The dipper dredge is capable of excavating from three to ten cubic yards of material per cycle. The boom limits dredging to a depth of not more than sixty feet. The ladder dredge is composed of a chain of small buckets each of which can excavate one to two cubic yards of material per bucket. The spoil is dumped from the buckets onto a belt and, generally, discarded over board. Dredqing in this manner is limited to a depth of approximately 100 feet. All the mechanical dredges are anchored to the bottom by three spuds which enhance the stability of the dredging platform. In each case, dredge material can be deposited directly next to the dredge site or into a barge for removal. Dredging by hydraulic pipeline has become a popular method of dredging. Material is picked up by a cutter head and pumped by suction through a pipe to the disposal site. The spoil created by hydraulic dredges is either pumped into the water directly adjacent to the dredge site or transported under hydraulic pressure up to two miles away through pipes. Pumping spoil greater distances 166 requires the use of "booster" pumps at a progressive increase in cost (Biggs, 1968). The hopper dredge is a self-propelled vessel which excavates material hydraulically but retains the spoil in hoppers. Once the dredge is loaded, it can proceed to a disposal area and purge the spoil through gates in the bottom of the hopper. A sixth type of dredging, called dredging "in the dry", is associated with man-made lagoons. Here, a canal is dredged from the landward end of a lagoon towards the water but is not opened to the water source inmmediately. Water is introduced into the lagoon only after excavation has been completed, through natural or mechanical destruction of the small strip of land separating the lagoon from the water source (Metzgar, 1973). Impact The primary impact of dredging for the purpose of aiding navigation is the direct physical destruction of the benthic (bottom) community of organisms. The primary impact of dredging for constructing lagoons is the physical destruction of wetlands. In both cases, many critical estuarine functions are affected in the areas that are dredged. The natural contour and composition of the substrate on which shellfish settle and grow is often removed through dredging as is the substrate which attracts fish to feed, spawn and grow, and waterfowl to nest in or migrate through certain wetlands systems. Similarly, problems are created in the areas in which the spoil material is deposited that often result in the destruction of important estuarine habitats (see Effects of Spoil Disposal). Aside from the actual physical destruction of habitat, dredging creates new flow patterns, in many cases introducing more saline waters into dredged areas. Salinity is an important factor to consider when dealing with estuarine 167 species since, in many cases, salinity is a limiting factor spatially and temporarily for both plants and animals (see General Principles of Wetlands Ecosystems). Deep holes left in the wake of extractive activity such as sand mining tend to trap organic detritus. Lack of water circulation in these deep holes leads to oxygen stratification and anaerobic decomposition of the detritus, characterized by the "rotten eggs" smell of hydrogen sulfide (Polis, 1974). Such conditions render an area uninhabitable for most forms of life. These holes represent a safety hazard for swimmers and clammers as well, who may fall into them without warning. Other disadvantages to dredging channels include increased turbidity; destruction of habitat from silt deposition; sedimentation of bays which promotes shoaling; increased saltwater intrusion; altered tidal exchange; altered mixing and water circulation patterns; and potential pollution of freshwater aquifers (Daiber et al., 1972; Copeland and Dickens, 1974). Newly dredged artificial dead end canals or lagoons produce habitats not suited for productive, diverse animal associations. Diaber et al. (1972, 1974, 1975) studied a total of eight artificial lagoon systems and a number of ad~joining natural embayments in the Little Assawoman, Indian River and Rehoboth Bays. South Bethany, the oldest dredged lagoon network in the state, was studied intensively. Flushing experiments, in which dye is released in lagoons, showed that the circulation and flushing rate of water in the dredqed lagoons was dangerously poor. Inadequate circulation and flushing leads to stratification of the water column especially in regard to its oxygen content, temperature and salinity. Oxygen demand in the water and sediments often leads to depletion of oxygen in the bottom water of the lagoons. Daiber et al. (1972, 1974, 1975) found lagoons that had no detectable oxygen present in bottom water layers. 168 FIGURE 53 LONGITUDINAL SECTION OF A DREDGE LAGOON, TYPICAL OF THE DEVELOPMENT AROUND THE SMALL BAYS IN DELAWARE Iraq ~~~~BULKHEAD :-YDREDGESPOIL5,~~~ BULKHEAD'~ ~MEAN HIGH WATER h FO _MRMRH MEAN LOW WATER FOR ME::NATURAL BOTTOM-- DREDGED LAGOON ANE MAR SH PEAT AND MU iiiarD~w~e ~~~~~. ...'--.~.~,B K EAD AREA OF LITTLE MIXING, AND CONSEQUENTLY OF OXYGEN, SALINITY, AND TEMPERATURE STRATIFI- CATION LEADING TO THE DEATH OF MOST OR- GANISMS. If not alleviated by the input of new oxygen-rich water into the system, these anoxic conditions can lead to the death of the organisms inhabiting the lagoon. In fact, in most cases the number and diversity of benthic fauna in natural areas was significantly greater than in lagoons. Similar results are documented for larval and adult finfish (Daiber, et al, 1972, 1974, 1975). In addition, runoff from yards and streets and leachate from sewage tanks from dredged lagoon housing developments tend to promote algal blooms, reduce dissolved oxygen and increase toxicity due to pesticides causing such undesirable results as fish kills and foul water (Clark, 1974) (see Residential and Commercial Development and Agriculture Discussions). The physical shape of dead end lagoons, the type most commonly developed along Delaware' s small bays, is the chief culprit (See Figure 53). It is not possible for water to circulate freely through the lagoon, first because there is only one opening to the lagoon and second, because a sill is often present in front of this opening. The sill prevents the free exchange of bottom water between the lagoon and the bay and permits only a thin surface water layer to move in and out with the tides (Daiber et al., 1972, 1974, 1975; Partington, 1973). It is rare that the dredged lagoon is ever completely flushed. Bulkheads are structures which are often used in association with marinas or dredged lagoon type housing developments (see Figures56-57). A bulkhead is a structure which generally runs parallel to the shoreline and which protects fastlands from wave action and prevents sedimentation of channels from upland erosion. Other forms of bulkheads include rip rap, a bulkhead composed of rock or concrete forms placed so as to dissipate wave energy or to collect sand along the shoreline; and groins, a shore protection structure built perpendicular to the shoreline to trap sand or sediment along the shoreline in order to retard erosion (see photos). 170 Bulkheading is a short term solution to a problem faced by developers of how to stabilize marsh banks and newly formed dredged spoil piles. However, there are many objectional side effects to bulkheading. First, bulkheading is extremely expensive and can cost a marina developer anywhere from 10 per cent Tor a 100 slip marina) to 18 per cent (for 50 slips) of his total investment. Ad- ditionally, adding bulkheads to the sides of lagoon systems exacerbates the problems of water circulation, waste accumulation, low dissolved oxygen, growth of exotic and noxious vegetation, algal blooms, fish kills and overall poor water quality, by curtailing nutrient exchange and physical and biological interactions between tidewaters and the mud bank, edaphic algae, cordgrasses and salt marsh animals. Bulkheading in the form of rip rap or groins can destroy long shore sediment drift resulting in starvation of the beach in certain areas and erosion in areas far removed from the actual bulkheaded structure. A good example of this effect is at Indian River Inlet where the groin associated with the inlet has curtailed the northward littoral drift of sediment. Consequently, sand has accumulated on the south shore and eroded on the north. Beneficial Effects In certain situations, it is possible that dredging releases nutrients from bottom sediments into the water, thus fertilizing the waters, rendering them more productive (Sherk, 1973). Dredging to maintain channels may improve water exchange and circulation, thus reducing flushing times. Finally, connecting isolated potholes or marshes to a source of water could increase production of an area by making areas available for spawning grounds and nurseries. Discussion The adverse effects of each dredging operation on the biology of estuaries varies according to the season, duration, and amount and mode of dredging. In 171 other words, each project that involves dredging and spoil deposition must be judged and planned individually. Knowledge of local conditions is critical. Data needs to be acquired to assess the impacts, both favorable and deleterious, of the proposed mode of dredging and spoil disposal on the dominant species of animals and/or plants found in the area. This type of planning will avoid costly mistakes by eliminating the needless destruction of natural shellfish beds and larval, juvenile or adult fish due to carelessness and lack of foresight. Since the information concerning impacts of dredge and spoil deposition (see Spoil Disposal) on the estuarine ecosystem and its components (the species involved) is known, it has been incorporated in the following recommendations. These recommendations are the basic conclusions reached by a variety of individuals who have spent a great deal of time and money looking into the effects of dredging. They are not mandates, but rather guidelines that should be considered in decisions about dredging in the estuarine zone. Factors Which Could Mitigate The following list of recommendations relates to dredging for maintenance of waterways (Maurer et al., 1974; Clark, 1974; Metzgar, 1973; Silberhourn et al., 1974; Marcellus et al., 1974). 1. Projects which benefit the public at large, rather than a small private interest should be qiven higher priority. 2. Dredging should be done in areas that do not threaten wetlands. 3. All dredging operations should be preceded by ecological feasibility studies in conjunction with economic and engineering studies. 4. Integrity of natural waterways should be maintained. 5. For small projects, a dragline is less environmentally damaging than hydraulic dredging and should be used. 172 6. Dredging in spawning and nursery areas, shellfish beds, or on areas of extensive submerged grass beds should be discouraged. 7. Dredging should be restricted to November through mid-March to avoid interference with migrations and spawning seasons of important finfish. 8. Dredging for the sole purpose of creating fill is unjustified. The following list of recommendations relate to dredging for the construc- tion of canals or lagoons (Daiber et al., 1972; Dalber et al., 1975; Metzgar, 1973; Partinqton, 1973). 1. Lagoon construction should be designed to facilitate water circulation, i.e., no dead end lagoons should be permitted. 2. If dead end lagoons are constructed, they should be no longer than twice their width. 3. For lagoons, dredging "in the dry" is less environmentally damaging. 4. Dredging should not be carried out below the natural water depths of the locality (no sills). 5. Dredging should not be done within the boundaries of the wetlands, nor should fill be placed on wetlands. 6. Residences should be placed on adjoining uplands. Proper community planning including density of housing, sewer systems, soil characteristics and land drainage should be accounted for. 7. Dredged lagoons should not be bulkheaded but gently sloped to allow natural vegetation to become established. References See References for Spoil Disposal. 173 Figure 54 Dredging Indian River Inlet Figure 55 Dredging Indian River Inlet 174 Figure 56 Rip Rap and Bulkheading Marine Center, Lewes Figure 57 Bulkheading Port Mahon 175 SPOIL DISPOSAL Spoil is the unused bottom material removed by the activity of dredging which must be either discarded or, preferably put to some constructive use. Spoil consists of sand, stiff clay, soft mud, muck (layers of organic material), shell, or other bottom material (Metzgar, 1973). When put to a constructive use, spoil becomes "fill" (Biggs,, 1968). Gravel, sand, shell and stiff clay have been used as fill to create fast land. Dredged shells can be used as a substrate to improve oyster production, Generally, soft mud is the most troublesome spoil--there are few construction uses for "soft mud' and "muck" (Biggs, 1968). Spoil disposal can be accomplished in three ways: by pumping or dumping spoil back into the water column, frequently adjacent to the excavation site, as when using hydraulic dredges with pipelines; secondly, by depositing spoil on land or wetlands, which may or may not be diked to prevent spoil from returning to the waterways, to create fast land or to stabilize existing land; finally, towing by scow or barge and dumping of spoil in deep water sites at locations distant from the dreging site (Metzgar, 1973). Effects of Spoil One major objection to the creation of spoil by dredging is that spoil is often deposited on wetlands. Since spoil deposit sites generally require that land become available at local expense, the lowest valued (in an economic sense) properties are sacrificed. Traditionally, the commion social perception that wetlands are worthless,thus establishing relatively low land values, renders them susceptible to being filled for this use (Metzgar, 1973). In terms of social value, such an activity would be creating usable fast land from "relatively worthless and useless marsh". It is only in recent years that researchers have 176 identified marshes as one of the most productive of all natural habitats, and also ones of great ecological value (see General Principles of Wetlands Ecosystems and Wetlands and Estuarine Productivity). Pumping spoil into a site adjacent to the actual dredge site is another damaging aspect of dredging and is potentially dangerous to the estuarine ecosystem. The primary objection to this activity is that high quantities of silt become suspended in the water, sharply increasing turbidity. Increasing turbidity decreases the amount of light penetrating the water and often leads to decreases in algal productivity (as indicated by the chlorophyll content of the water) during dredging operations (Sherk, 1973). Suspended sediment also exerts an oxygen demand on the water column up to eight times that of the same material deposited on the bottom (Issac, 1965). This can be critical during the hot months of the year when the water is warm and the dissolved oxygen concentrations relatively low. Suspended sediment, in addition to fertilizing the waters (discussed later), also introduces toxic materials that are deposited in some bottom sediments. Baltimore Harbor, for instance, contains high concentrations of "heavy metals" (cadmium, zinc, etc.) which can be highly toxic to aquatic life (Biggs, 1968). These heavy metals can also be concentrated in organisms like fish and cause illness in humans when consumed. The effect of suspended sediments on macroscopic biological life is not well understood but some knowledge concerning specific species is available. Species such as the oyster (Crassostrea virginica) are extremely tolerant of high silt loads as are other eip- and infauna whi~ch must contend with naturally occurring silt loads in the estuary at certain times of the year. However, unnaturally high silt loads associated with dredging have been found to be deleterious to more sensitive stages of the life cycles of many estuarine 177 organisms (Sherk, 1973; Schubel et al., 1974; Auld and Schubel, 1974). The growth and survival of clam and oyster egqs and larvae, for instance, are perturbed at suspended concentrations as low as 125 mg/1 (Davis, 1960). Con- sequently, it has been recommended that concentrations of suspended material should not exceed 100 mq/1 in estuaries (Sherk, 1973). This value is flexible in terms of the type and duration of the suspended sediment and the time of year at which the deposition is to occur. Sherk et al. (1972) tested the effects of suspended sediment on various estuarine species of fish. They classified Atlantic silverside, juvenile bluefish, juvenile menhaden, and the young of the white perch as highly sensitive to sediment load. The mummichog and striped killifish proved most tolerant of all species tested. It was found that 580 mg/1 of suspended sediment was all that was required to produce 10 per cent mortality in silverside populations. However, it took 23,000 mg/l to kill 10 per cent of the samples of mummichogs and killifishes (Sherk el al., 1972). As the silt begins to settle, bottom living organisms such as clams, oysters, crabs, shrimp and other benthic organisms are covered. Benthic communities completely smothered require from one to two years for reestablishment. Loss of benthic life effects other animals in higher trophic levels such as fish and waterfowl. In Florida, it was found that after dredging, no bottom species (such as flounders) were found in an area once able to support a great variety of bottom fishes, apparently because of a lack of food organisms in the sediment (Sherk, 1973). Since many estuarine fishes have demersal eggs (eggs that sink to the bottom), deposition of suspended sediment in estuaries and tidal creeks during spawning periods could foreseeably destroy a brood stock, striped bass for instance (Mansueti, 1961). Layers of dead oysters have been created because of the intermittant deposition of spoil in Florida and the upper Chesapeake 178 Figure 58 Dredge Spoil Disposal Lewes-Rehoboth Canal Figure 59 Solid Waste Used as Fill Smyrna River 179 Figure 60 Dredge Fill and Bulkheading White Creek Figure 61 Dredge Spoil Disposal Pile Indian River Inlet 180 (Sherk, 1973). Thoughtless spoil deposition, then, can lead to reduced fish and shellfish harvest which, if continued, leads to biologically dead areas of little use to anyone. In all cases, aspects of mortality, decreased yield, and interferences with energy flow have been identified by researchers as a result of spoil deposition on wetlands and bottom communities. Similarly, sublethal effects on life cycles, reproduction and growth of organisms are apparently due to exposure to factors associated with spoil deposition. In Delaware, Maurer et al. (1974) have constructed a comprehensive scenario of the effects of dredging and spoil deposition on benthic invertebrates. In March 1972, the Lewes ferry approach in Lewes, Delaware, was dredged and the spoil was deposited on the northeast side of the Inner Breakwater in the Harbor of Refuge. Approximately 191,000 cubic meters of sandy material was dredged hydraulically. There was a significant reduction in density of benthos at the dredge and disposal sites after dredging. The abundance of two dominant snecies, both mollusks (Nucula proxima and Tellina agilis), declined significantly. The reduction in animal density and community disruption of benthic invertebrates was restricted to the dredge and spoil areas. Three months after the activity, some recruitment of benthic invertebrates had occurred at the spoil disposal site. Since dredging is a reality and a necessity for maintenance of ship channels, it is the disposition of the spoil deposit, a component of dredging, which must concern us. The alternatives for spoil deposition are based on social, economic and ecological considerations, each of which must be assessed and weighed. Uses for spoil deposits satisfying all sectors are rare. 181 Beneficial Effects There is evidence to support the idea that dredging fertilizes the waters due to the increase in turbidity through nutrient release, although the effect is not an immediate one (Sherk, 1973). However, it is possible that if the spoil contains toxic substances, these are also released into the waters. Recommendati ons The following is a list of recommendations concerning the deposition of spoil (Clark, 1974; Daiber et al., 1972, 1974, 1975; Marcellus et al., 1973; Silberhorn et al., 1974; Metzgar, 1973; Maurer et al., 1974; Sherk, 1973). 1. Spoil should not be placed on high value natural habitat. These include: marshes, beds of submerged vegetation, protected shallows, oyster reefs, tidal guts. 2. Spoil suitable as "fill" for uses as residential, commercial, and industrial development should be used for such. Spoil shells can be used to stimulate oyster production or for building dikes. Constructive alternative uses for spoil should be researched. 3. Abandoned sand and gravel pits in proximity to the water where spoil can be contained from running off or polluting freshwater supplies should be used as spoil receptacles. 4. Under certain conditions, it might be possible to enchance or create new marsh from spoil. 5. Natural channels should not be blocked with spoil. 6. Spoil should not be placed back in the water, if possible, but rather on the uplands. Constraints should be placed on types of materials which can be disposed of in open water. 7. If spoil is to be placed in the water, it should not be placed closer than 500 feet from shorelines of shallow protected bays. To provide maximum 182 water exchange and circulation, spoil should be placed alternately in mounds on each side of the channel. 8. Spoil deposition sites should be planned to allow future maintenance as in the creation and development of spoil islands which have been found to be beneficial for terrestrial habitat and migratory waterfowl. 9. Prior to full-scale dredging there should be a determination of the physical and chemical characteristics of the spoil in order to decide the most appropriate dredge spoil fate. 10. Beach nourishment and spoil are related problems that should be approached jointly. 11. Temporal aspects of spoil deposition should include consideration of biological factors like spawning seasons, fishing grounds, etc. 12. Spoil deposition in areas of high flushing rate will decrease damage due to suspended sediment and oxyqen depletion. References Auld, A. H. and J. R. Schubel. 1974. Effects of suspended sediment on fish eggs and larvae. CBI. The Johns Hopkins University, Ref. 74-12, Spec. Rept. 40. Biggs, R. B. 1968. The magnitude of the snoil disposal problem. FWPCA public hearing, Annapolis, Maryland. October 30, 1968. University of Maryland, Chesapeake Biological Lab., Ref. #68-90. Clark, J. 1974. Coastal Ecosystems. The Conservation Foundation, Washington, D. C., 178 pp. Copeland, B. J. and F. Dickens. 1974. Systems resulting from dredging spoil. In: H. T. Odum, B. J. Copeland and E. A. McMahan, eds. Coastal Ecological Systems of the United States. The Conservation Foundations. Volume III, 453 pp. Daiber, F. C., P. Aurand, H. Bailey, P. Feldheim and K. Theis. 1972. Environ- mental impact of dredge and fill operations in tidal wetlands upon fisheries biology in Delaware. CMS. University of Delaware. 93 pp. Daiber, F. C., D. Aurand, W. Bailey and G. Brenum. 1974. Ecology effects upon estuaries resulting from lagoon construction, dredging, filling, and bulkheading. Cr!S. University of Delaware. 183 Daiber, F. C., D. Aurand, G. Brenum, and R. Clarke. 1975. Ecological effects upon estuaries resulting from lagoon construction, dredging, filling, and bulkheading. CMS. University of Delaware. 197 pp. David, H. C. 1960. Effects of turbidity-producing materials in seawater on eggs and larvae of the clam (Venus (Mercenaria) mercenaria). In: J. A. Sherk, Jr. 1972. Current status of the knowledge of the biological effects of suspended and deposited sediments in Chesapeake Bay. Ches. Sci. 13: S137-S144. Issac, P. C. G. 1965. The contribution of bottom muds to the depletion of oxygen in rivers and suggested standards for suspended solids. In: J. A. Sherk, Jr. Current status of the knowledge of the biological effects of suspended and deposited sediments in Chesapeake Bay. Ches. Sci. 13: S137-S144. Mansueti, R. J. 1961. Effects of civilization on striped bass and other estuarine biota of Chesapeake Bay and tributaries. In: J. A. Sherk, Jr. 1972. Current status of the knowledge of the biologiTal effects of suspended and deposited sediments in Chesapeake Bay. Ches. Sci. 13: S137-S144. Marcellus, K. L., G. M. Dawes and G. M. Silberhorn. 1973. Local management of wetlands--environmental considerations. VIMS. Spec. Report. No. 35. 94 pp. Maurer, D., R. Bigqs, W4. Leathem, P. Kinner, W. Treasure, MP. Otley, L. Watling and V. Klemas. 1974. Effects of spoil disposal on benthic communities near the mouth of Delaware Bay. CMS. University of Delaware. 231 pp. Metzgar, R. G. 1973. Wetlands of Maryland. Department of State Planning, Baltimore, Maryland. Partington, W. M. 1973. Environmental impacts--the Florida study. In: Canals and waterfront development, conference summary. Salisbury State College. 26 pp. Schubel, J. R., A. H. Auld, and G. M. Schmidt. 1974; Effects of susnended sediment on the development and hatching success of yellow perch and striped bass eggs. CBI. The Johns Hopkins University. Spec. Rept. #35. Sherk, J. A., Jr. 1972. Current status of the knowledge of the biological effects of suspended and deposited sediments in Chesapeake Bay. Ches. Sci. 13: S137-S144. Sherk, J. A., J. M. O'Conner and D. A. Neumann. 1972. Effects of suspended and deposited sediment on estuarine organisms. Phase II. Department of Environmental Research, CBL. Ref. -72-9E. 167 pp. Silberhorn, G. M., G. M. Dawes and T. A. Barnard. 1974. Coastal wetlands of Virginia. Interim Report Number 3. VIMS. Special Report Number 46. 52 pp. 184 IMPOUNDING Definition and Description Impounding a marsh or wetland area is the act of placing embankments around the area to effectively stop the natural tidal flow. The marsh is then flooded with water or, alternatively, water that is already present is trapped behind the embankments and the area is converted into a shallow pond. Fre- quently, a saltwater environment is thereby changed to a freshwater habitat. Thus there may be two functions for an embankment or dike, both to retain interior water and to exclude exterior water. Impoundments can take several forms. In high level impoundment,dikes with tide gates interspersed are built around a marsh. Saltwater is then effectively prohibited from entering the marsh and freshwater from upland drainage enters the impounded area creating a freshwater community. Generally, the tide gates do not let saline water into the impoundment but are, rather, only opened at low tide to let freshwater escape from the impounded area. This "1drawdown" is part of the management technique with high level impoundments. In low-level impoundments, tidal flow is interrupted but not eliminated. Water control is achieved through the use of sluice gates. Sluice gates hold a specified level of water in the system at low tide but allow water to enter the system at high tide. Pools (usually 15-30 feet in diameter and from 3-6 feet deep) for mosquito control are frequently constructed on the marsh surface by dragline or by blasting with dynamite. These so called "champagne pools" are interconnected by ditches which often lead to depressions in which mosquitos could breed. In this way, mosquito-eating fish can move from one area to another. In the past, dikes were constructed that merely excluded saltwater. This type of water management was undertaken to create areas for the production of salt hay (Spartina patens), primarily for grazing sheep and cattle. At 185 the present time, however, the major reason for impounding marsh area is to encourage waterfowl utilization and to control mosquitos in areas where there is little tidal fluctuation. Effects As may be expected, permanent flooding of a marsh area with freshwater causes extensive changes in both flora and fauna. Vegetation undergoes a change from the grasses typical of salt marshes to plants more characteristic of fresh and brackish water communities. Submerged and emergent vegetation become much more abundant and there is a regression in the natural succession of a marsh back to a more open water community. A gradual accumulation of sediment and the evolution towards high marsh and upland associations of plants is regarded as the normal sequence of an accreting marsh; impounding reverses this trend, at least temporarily. Springer and Arsie (1956) found that in Bombay Hook, Delaware, creating a high level impoundment of a salt marsh produces vegetation changes from cordgrass (Spartina alterniflora) marsh to pondweed (Potomogeton berchtoldi and P. pectinatus) and widgeon grass (Ruppia maritima) with algal mats in the center. Around the edge of the water, a number of emergent species become abundant. These include three-square (Scirpus americanus), marsh mallow (Hibiscus moscheutos), cattails (Typha spp.), giant reed (Phragmites communis), and switch grass (Panicum virgatum). A few localized areas of marsh plants may persist after impounding, the abundance of which is dependent upon the extent of inundation. In the Little Creek (Tindall, 1961) and Assawoman Wildlife areas (Florschutz, 1959), salt marsh cordgrass (S. alterniflora), spike grass (Distichlis spicata), bulrushes (Scirpus spp.), marsh mallow (Hibiscus spp.), high tide bush (Iva frutescens), and groundsel bush (Baccharis 186 halimifolia) were reduced in abundance and were replaced by open water and emergent vegetation including pondweed (Potomogeton spp.) and widgeon grass (Ruppia maritima) beds, cattails (Typha spp.), wild millet (Echinoclva), chufa (Typerus spp.) and muskgrass (Chara spp.). Salt hay (Spartina patens) was greatly reduced in the middle of the impoundments, but grew well along the edges. Smith (1968) in his study of low level impoundments south of Leipsic and on the Murderkill reported that the overall density of cordgrass(S. alterniflora)decreased but that the density of other plants increased dramatically, especially along pools, ditches and adjacent spoil banks. The higher salinities found in these low level impoundments also cause an increase in the salt tolerant species as salt hay (S. patens), spike grass (D. spicata), high tide bushes (Iva frutescens) and groundsel bushes (Baccharis halimifolia). Smith (1968) reported an increase of the groundsel bush (Baccharis) and the common reed (Phragmites) on spoil piles and embankments. Obviously, the species of the plants which become abundant are dependent upon local geographic and climatic factors. Catts et al. (1963) found that impounding drastically changes the number and species composition of the mosquito population in Delaware salt marshes. Im- pounding practically eliminates the breeding of the salt marsh mosquito, Aedes sollicitans. This mosquito is the most obnoxious of those that breed in the marsh. It is a strong flier; flights as far as 100 miles from the marsh in which the mosquito was bred have been recorded. The female (the only sex that bites) is extremely persistent and will attack during both day and night but especially as dusk approaches. Tindall (1961) found that in the Little Creek area impounding tends to increase the production of other, more permanent water mosquitosspp. (Culex salinarius, Anopheles bradleyi, and Uranotaenia 187 sapphirina). Fortunately though, these species do not have the nuisance value of the salt marsh mosquito as they have short flight patterns, fly primarily at night and have different biting habits. The water level of the ponds de- termines the magnitude and type of mosquitos produced, and it is believed that nroper timing and water control management will reduce this breeding to a minimum. Control of the biting flies by impounding is difficult to achieve. It is believed that certain of the Tabanid species (qreenheads) are controlled by the summer "draw-down" process on high-level impoundments and it appears that the species composition of the flies produced is changed. Harrison (1970) in his studies in marshes near Leipsic and on the Murderkill and Broadkill Rivers, suggests that there is little effect on tabanid production in low- level impoundments, at least during the first year after impoundment. Chemical control of the flies appears to be impractical as the larvae mature slowly in the sediment of the marsh. Applications of larvicide would thus have to be frequent and/or at prohibitively high concentration in respect to the rest of the biota of the marsh and estuary. Capture of mature adults appears to be a useful control technique. There is little concrete information on changes in invertebrate populations after impounding in Delaware or anywhere else (Daiber, 1972). Obviously, a large change in habitat occurs, both physically (flooding of the marsh surface) and biotically (destruction of flora). One would expect that almost all of the invertebrates of the marsh would be eliminated except those that may persist along the margins of the ponds. Salinity changes and loss of land area would probably cause this result. The absence of fiddler crabs in impoundments has been documented and appears to be evidence for this hypothesis. Impounding areas to produce salt hay has been found to decrease the numbers of fiddler crabs (Uca spp.), snails (Littorina irrorata and Melampus bidentatus) and mussels (Modiolus demissus). These invertebrates form an important part of the diets of clapper rails, black ducks and other higher animals (Ferrigno, 1961). Changes in the lower rungs of the food chain (as the invertebrates, for instance) are reflected in changes at hiqher levels (as in fish production or waterfowl prevalence). After impounding, clapper rail populations have often disappeared. This is believed to be associated with the absence of fiddler crabs (Darsie and Springer, 1957; Mangold, 1962; Shoemaker, 1964). Decreases in some populations of small perching birds (passerine birds) after impounding have been shown in several studies. Decreases in these birds (such as the song sparrow, seaside sparrow, sharptail sparrow, and yellow throat warbler) are believed to be due to the loss of nesting sites and food (Mangold, 1962; Shoemaker, 1964). A decrease in bird usage has been found in marshes that are being managed for salt hay production. Waterfowl and wading bird usage of marsh areas in Delaware has been found to tremendously increase after impounding and it is for this reason that marshes are often impounded (Catts, 1957; Florschultz, 1959; Tindall, 1961; Lesser, 1965; Smith, 1968). The ponds serve as excellent resting, feeding and breeding areas for waterfowl. Both numbers of individuals and numbers of species have been increased by impounding. Breeding has also been found to increase over the unmanaged, natural marsh. Areas of open water with emergent vegetation have been found to be optimum for most ducks and geese--these conditions are created by impounding. Increased fish populations attract species of fish-eating birds such as the snowy egret, American egret, least bittern, green heron, greater and lesser yellowlegs, pectoral sandpiper, 189 common and lesser terns. In Bombay Hook, Darsie and Springer (1957) identified eighty-six species of birds after impounding as opposed to fifty-five species in the same areas before impounding. Smith (1968) in two Delaware marsh test sites (near Leipsic and on the Mispillion River) found a total of sixty-two species of birds on the impounded areas and thirty-nine species in the natural marsh areas. Tindall (1961) in the Little Creek impoundment reported a three-fold increase in birds, The amount of fishlife increases when a marsh is impounded. This is expected since the volume of water in an impoundment greatly exceeds that of the natural marsh. Fish species normally associated with the tidal creeks and marshes can be expected to occur in impoundments. Smith (1968) found several species of fish including the mummichog (Fundulus heteroclitus), striped killifish (Fundulus majalis), eel (Anguilla rostrata) and the sheeoshead minnow (Cyprinodon variegatus) in low level impoundments in his Leipsic and Mispillion test sites. Carp are usually found in impoundments that are less saline. As time passes, the number of soecies of fish tend to increase and to become more freshwater in character in high level impoundments. Such fish as the bullhead (Ictalurus nebulosus), pickerel (Esox americanus) and the pumpkinseed (Lepomis gibbosus) become established. Bullfrogs (Rana catesbiana) and snapping turtles (Chelydra serpentina) also begin to appear. Mammalian usage of a marsh is also believed to increase after impounding. Muskrat usage is encouraged in high level impoundments by the increased pro- duction of preferred food plants like Scirpus and typha. Darsie and Springer (1956) found that the maintenance of high water levels within high level impoundments tended to restrict usage by muskrats, but that a decrease of water level during the summer encouraged the growth of plants attractive to 190 muskrats and waterfowl. An increase of salinity (caused by storm washover or evaporation) caused a decrease in the muskrat population due to losses of food and drinking water. Smith (1968) felt that since low level impoundments often increase salinity in the summer, killing Scirpus and Typha, a reduced muskrat population would occur. Smith (1968) found no direct evidence of an increased small mammal popula- tion in low level impoundments near Leipsic and on the Murderkill. However, there did appear to be evidence that an increase in the number of mammalian predators in the low level impoundments had occurred. Smith (1968) concluded that the increased habitat diversity of low level impoundments lead to a greater variability of animals. Much of this increased diversity is due to the creation of dikes and embankments producing environments. Impoundments produce "edge" (a sharp transition zone between two distinct habitats) in several ways. The construction of dikes creates a suitable habitat for upland vegetation valuable as food for wildlife (such as poke weed and foxtail grass). The less desirable high tide bush (Iva frutescens) and groundsel bush (Baccharis halimifolia) are also present, however. The embankments and adjoining emergent plants provide food, shelter, and nesting areas for a greater number of prey and predator species than were present originally. And, in addition, the dikes serve as routes for travel for terrestrial organisms as to ditches for aquatic animals. One of the most important functions of a marsh is its ability to supply nutrient-rich water to the estuary. High level impoundments eliminate nutrient exchange. A three-year study has shown that the exchange of phosphorus, an important nutrient present in relatively high concentrations on the marsh, between a high level impoundment and the adjacent estuary to be among the lowest for all managed marshes (Reimold, 1969). This decrease in available nutrients may have profound effects on the fertility of the estuarine food 191 Figure 62 Impoundment Little Creek Wildlife Area Figure 63 Impoundment Bombay Hook 192 Figure 64 _ t it Sluice Gate Woodland Beach Wildlife Area Figure 65 Tide Gate Bombay Hook 193 chain. The use of the marsh as a spawning and nursery ground for estuarine species has also been prevented by its conversion to an impoundment. Finally, intrinsic costs of maintaining impoundments must be considered. An improperly managed impoundment due to lack of funding is tantamount to an ecological disaster. Tide gates, sluice gates and dikes must have proper maintenance. Management of water level in high level impoundments is critical in terms of reducing obnoxious pests and in attracting desirable waterfowl populations. In conclusion, impounding a marsh has many beneficial as well as adverse effects. It is a useful and successful management technique when one's goals have been defined as mosquito control and waterfowl production. Obviously, many of the characteristics of a natural marsh are lost when the impoundment is separated from the estuarine system. Other useful activities not present in a natural marsh are, in turn, fulfilled by the impoundment. What is therefore achieved is a tradeoff. All marshes should not be converted into impoundments, but on the other hand, the presence of some impoundments may enhance the coastal area and man's enjoyment of it. References Catts, E. P., F. H. Lesser, R. F. Darsie, 0. Florschutz, E. E. Tindall. 1963. Wildlife usage and mosquito production on impounded and tidal marshes in Delaware. 1956-62. Miscellaneous paper Number 443. Delaware Agriculture Experiment Station Publ. Number 338. Daiber, F. C. 1972. Tide marsh ecology and wildlife: salt marsh plants and future coastal salt marshes in relation to animals. Annual Pittman- Robertson Report. College of Marine Studies, University of Delaware. Project Number W-22-7. 80 pp. Darsie, R. F., Jr. and Springer. 1957. Three-year investigation of mosquito breeding in natural and impounded tidal marshes in Delaware. University of Delaware Agriculture Experiment Station Bull., 320. 65 pp. Ferriqno, F. 1961. Variations in mosquito-wildlife associations on coastal marshes. In: F. C. Daiber. Tide marsh ecology and wildlife. College of Marine SRudies, University of Delaware. Project Number W-22-7. 80 pp. 194 Florschutz, 0., Jr. 1959. Mosquito production and wildlife usage in impounded, ditched and unditched tidal marshes at Assawoman Wildlife Area, Delaware. Proc. N. J. Mosq. Exterm. Assoc. 46: 103-111. Harrison, F. J., Jr. 1970. The use of low-level impoundments for the control of the salt marsh mosquito, Aedes sollicitans (Walker). Master's thesis. University of Delaware. Lesser, F. H. 1965. Some environmental considerations of impounded tidal marshes on mosquito and waterbird prevalence, Little Creek Wildlife Area, Delaware. Master's thesis. University of Delaware. 121 pp. Mangold, R. E. 1962. The role of low-level dike salt impoundments in mosquito control and wildlife utilization. Proc. N. J. Mosq. Exterm. Assoc. 49: 117-120. Reimold, R. J. 1969. Evidence for dissolved phosphorus hypereutrophication in various types of manipulated salt marshes of Delaware. Ph.D. dissertation. University of Delaware. 169 pp. Shoemaker, W14. E. 1964. A biological control for Aedes sollicitans and the resulting effect upon wildlife. Proc. N. J. Rosq. Exterm. Assoc. 51: 93-97. Smith, D. H. 1968. Wildlife prevalence on low-level impoundments used for mosquito control in Delaware, 1965-1967. University of Delaware. Master's thesis. 83 pp. Springer, P. F. and R. F. Darsie. 1956. Studies on mosquito breeding in natural and impounded coastal salt marshes in Delaware during 1955. In: F. C. Daiber. Tide marsh ecology and wildlife. Annual Pittman- Robertson Report 1972. Project Number W-22-7. 00 pp. Tindall, E. E. 1961. A two-year study of mosquito breeding and wildlife usage in the Little Creek impounded salt marsh, Little Creek Wildlife Area, Delaware, 1959-60. Master's thesis. University of Delaware. 121 pp. DITCHING Definition and Description Ditching is the physical act of creating a network of narrow and shallow channels on the surface of the marsh. Ditches are cut through the marsh by plows, or entrenching machines (see photo). Permanent pools and low areas are, therefore, connected to the tidal creeks, and water on the marsh surface is effectively drawn off. Ditching is usually done in a regular pattern, most 195 often one of parallel lines a set distance apart. Dredge material taken out of the ditches is deposited on either side of the ditch. The vast majority of the marshes in Delaware were ditched (approximately 44,000 acres, mostly Zones I and II) by the Civilian Conservation Corps (CCC) during the depression years of the 1930's. Ditching was initiated to control the salt marsh mosquito, Aedes sollicitans, considered a major pest due to its extended flying range and ferocious bite. It has been previously found that the frequency of inundation of a marsh area largely determined its suitability for the salt marsh mosquito production. Shallow standing water that was infrequently flushed was discovered to be the optimum condition for the breeding of salt marsh mosquitoes. By ditching the marsh, it was theorized that these areas would be drained and that the channels would expose the mosquito larvae in the pools to predation by killifish, mosquito fish and other mosquito consuming fishes. Adverse Effects Indiscriminant ditching of marshes has been found to be destructive to the existing flora and fauna of marshes (Cottam et al., 1938; Bourn and Cottam, 1939, 1950; Cottam and Bourn, 1952; Stearns, MacCreary and Daigh, 1939, 1940). It is the general conclusion of these investigators that ditching effectively drains the marsh, converting low marsh into a community more characteristic of the high marsh and upland. In effect, ditching raises the elevation of the marsh. In a New Castle County marsh, Stearns, MacCreary and Daigh (1940) found that the water table dropped 5.03 inches in three years following ditching. This type of perturbation drastically effects the zonation of plants in the marsh, creating a higher, drier, type of environment. Cottam, et al., (1938) found that in Delaware, high marsh plants such as salt marsh fleabane (Pluchea 196 camphorata) and salt marsh aster (Aster subulata) quickly invade recently ditched areas. These species are then followed by the high tide bush (Iva frutescens) and groundsel bush (Baccharis halimifolia) which initially take root on the higher ground of the spoil piles on the sides of the ditches. Stands of these plants are not as productive as low marsh vegetation nor do they contribute and recycle nutrients into the water column as effectively as low marsh plants, cordgrass (Spartina alterniflora) in particular. Bourn and Cottam (1950) found in a test area on the Mispillion River, pure stands of cordgrass (S. alterniflora, Zone I, the most prevalent and productive low marsh species in Delaware) were replaced eventually by either the groundsel bush or high tide bush (Zone III) within five years after ditching. While cordgrass had once covered 90 per cent of the area in 1936, by 1941 it covered only 32 per cent. Concommitantly, the effective coverage by the two salt bushes had increased eight-fold to cover 39 per cent of the area. Essentially, the highly desirable and productive Zone I marsh is replaced by the less productive Zone III marsh (see Wetlands Zones and Properties). Drainage of the permanent pools on the surface of the marsh has been sugqested as the single most damaging factor to wildlife from ditchinq. These pools often support beds of widgeon grass (Ruppia maritima), an excellent food for waterfowl (Cottam, et al., 1938). The pools thus supply food, drink and shelter for wildlife. Drainage often destroys these characteristics of the pools, either by drying them out or by permitting the intrusion of higher salinity water, thus killing the grass. Along with the floral replacement, drastic modifications in the fauna of the marsh often occur. Many of these permutations are a direct result of the floral changes caused by ditching. Changes in vegetation alter the microhabitats of marsh invertebrates causing stress. Ditching has been labeled 197 responsible for marked decreases of invertebrates (mostly molluscs and crustacea). Cottam et al., (1938), Bourn and Cottam, (1939, 1950) found decreases in the invertebrate populations in four plant communities they studied before and after ditching. Vegetation Type Invertebrate Change Salt marsh cordgrass (Spartina alterniflora) 43.5% decrease Salt marsh bulrush (Scirpus robustus) 92.6% decrease Spike grass (Distichlis spicata) 71.9% decrease Salt hay (Spartina patens) 84.2% decrease The decrease in each case represents a reduction in numbers as well as a reduction in species. The lowering of the water table attributed to ditching tends to increase drying and oxidation of sulfides, which produce more acidic conditions than are associated with normal marsh muds (Nealy, 1962). These more acid conditions contribute to the decline of invertebrates especially the molluscs and crus- taceans, which are dependent upon alkaline conditions for the construction and maintenance of their shells and exoskeletons. Invertebrates are staple items in the animal diets of many birds and animals; especially of many ducks. Thus both food and shelter areas for waterfowl and other birds may be greatly reduced and populations are, therefore, decreased. The cutting of ditches also permits the intrusion of saline water into regions of the marsh that were formerly brackish or relatively fresh. This adds to the disturbance of the flora caused by lowering water tables. Stearns, MacCreary, and Daigh (1939, 1940) found in their studies in Kent and Sussex Counties that muskrat populations and individual weights decrease as the species of plants that are preferred foods of the muskrat (Olney's three-square, 198 Scirpus olneyi, and big cordgrass Spartina cynosuroides) were replaced with less favorable species because of saltwater intrusion. Apparently, ditches have little effect on reducing tabanid fly production. Tabanid flies are distributed in larval form throughout the lower salt marsh principally in areas below mean high tide dominated by cordgrass (Zone I, S. alterniflora). Dukes et al. (1974) found that the drainage effects of ditches on tabanid production was effectively negated by the degree and regularity of tidal inundation in the lower marsh. They further state that control measures for tabanids in Zone I are inadvisable due to the vast areas which would have to be manipulated and to the deleterious effect control measures, as ditching, would have on the nutrient exchange between the low marsh and the water column. There is some evidence that ditching increases the availability of breeding areas for tabanids (Baily, 1948; Hansens, 1949; Rockel, 1969) by increasing the area of marsh below mean high water. Finally, Connell (1940) demonstrated that the ditching of low cordgrass (S. alterniflora) marshes did not control the breeding of the marsh mosquito, and, Stearns, et al., (1940) suggested that the ecological side effects of ditching greatly outweighed the benefits. Beneficial Effects Ditching has been shown by many investigators to have beneficial effects on flora and fauna (Headlee, 1939; Cockran, 1938; Ferrigno, 1961; Catts, 1957; Florschutz, 1959; Lesser, 1975). Stewart (1951) and Ferrigno (1961) found that ditching encourages cordgrass (S. alterniflora, tall form) growth on the edge of the ditches which provides more shelter and nesting sites for rails and black ducks (edge effect). Ditching also effectively limits breeding of mosquitoes in areas formerly designated as trouble spots. Stearns, MacCreary 199 and Daigh (1940) found that during experimental ditching in the Appoquinimink marshes, mosquito production was virtually halted. Studies by Catts (1957) and Florschutz (1959) in Assawoman Wildlife Area concur with this study. Cockran (1938) concludes that ditching has no effect on muskrats in Delaware but may have actually caused an increase in their production. Ditching a marsh may increase the flushing of the high marsh, which normally is very seldom inundated. This makes available previously untapped sources of productivity to the adjacent estuarine system -- thus increasing the amounts of detritus and nutrients available for use in the food chain. Lesser (1975) in his study of a section of the Mispillion marsh indicates that some species are more abundant on ditched marshes than on unditched, such as the fiddler crabs (Uca minax and Uca pugnax). This is made possible by increasing the amount of marsh surface at mid-tide levels because of ditch bank slumping (Rockel, 1969). Headlee (1939) believed that ditching did not lower the water table nor did it have any appreciable effect on marsh vegetation or adverse effects. Mitigating Measures A considerable amount of evidence has accumulated to suggest that when ditching must be undertaken, only the high marsh (Zones II, III) should be ditched. These two zones produce the majority of salt marsh mosquito. Low marsh areas (Zone I), transition marshes (Zone V), and arrow-arum, pickerel weed marshes (Zone VI) produce few salt marsh mosquitoes (Aedes sollicitans) because they are frequently inundated (Connel, 1940). Ditching these areas is unnecessary and a decrease in the amount of ditching decreases the magnitude of the adverse effects. It is the damp infrequently flushed areas of the high marsh which produce the vast quantities of mosquitoes (Clark, 1974). Therefore, 200 ditching should be selective rather than wholesale. Research into different types of ditches indicates that some techniques are less damaging than others. Draining the high marsh by digging relatively short blind channels (similar to radiating spokes) from a central 'champagne pool' is believed to be less environmentally destructive than ditching the high marsh indescriminantly. The 'champagne pool' allows mosquito consuming fish to reside in the high marsh during the productive summer season. This 'home base' is extended on spring tides and during storms when the radiating spokes become filled with water. The fish then gain access to the mosquito rich high marsh and consume the larvae. The size and depth to which the ditches are dug is an important variable in the effect of ditching. Price (1938) suggested that if shallow ditches connected to tidal ditches are constructed to drain the high marsh, there may be a beneficial effect. The shallow ditches would permit the intrusion of water during the flooding tide, thus maintaining water levels and facilitating fish predation Of mosquito larvae. Deep, wide, and straight ditches are to be recommended according to Ferrigno and ~Jobbins (1968) as they will not be as rapidly filled or blocked by marsh slumping. liaterial taken from the ditches should be trampled or mashed into the marsh surface rather than being merely piled and should be alternately spaced on both sides of the ditch rather than on one side creating a circulation barrier In summary, ditching of low cordgrass marshes (Zone I) accelerates the evolution of low marsh to high marsh, has a relative deleterious effect on wildlife, and inhibits the crucial interaction between cordgrass and estuarine waters. It also has limited success in reducing mosquito and tabanid fly production significantly in cordgrass marshes. However, ditching of the high 201 marsh (Zones 1I and 111) when properly applied appears to greatly control mosquito production by draining surface water and increasing flushing. Secondly, ditching of high marshes appears to have a minimal effect on the ecology of the area. An indepth sunmmary of the effects of ditching in the marsh can be found in Daiber (1974). Conclusions and Recommendations 1. Indiscriminate ditching of all marshes is impractical, costly, unnecessary and ecologically destructive. 2. Ditching of low Spartina alterniflora marshes (Zone I) does not significantly reduce mosquito production or tabanid fly production and causes irrepairable harm to the marsh from an ecological standpoint. 3. Ditching and/or creating 'champagne pool' networks on the high marshes designated by scientists as high mosquito producing areas can significantly reduce mosquito production and causes a relatively low amount of ecological harm to the marsh. 4. Ditching of any part of the marsh appears to have little effect on reducing tabanid fly production and therefore should not be considered as a tool for regulating fly production. 5. Ditches, when constructed, should be deep, wide and straight so that they will not fill in nor will they become clogged but rather be open to tidal flow. 6. Ditches in high marsh areas should be maintained and more studies on the effect of ditches on the high marsh proper, on mosquito production and tabanid fly production initiated. 7. Ditches should be constructed through the low cordgrass marsh (Zone I) only when said ditches are acting as access canals for tidal flow to higher marsh areas. 202 Figure 66 Ditching Pickering Beach Area Figure 67 Ditching Pickering Beach Area 203 References Baily, N. S. 1948. A mass collection and population technique for larvae of Tabanidae (Diptera). Bull. Brooklyn Ent. Soc. 43: 22-29. Bourn, W. S. and C. Cottam. 1939. The effect of lowering water level on marsh wildlife. In F. C. Daiber, 1974, Tide Marsh Ecology and Wildlife. CMS. University of Delaware. 80 pp. Bourn, W. S. and C. Cottam. 1950. Some biological effects of ditching tide- water marshes. Res. Rept. 19, Fish and Wildl. Serv., U. S. Dept. of Interior. Catts, E. P., Jr. 1957. Mosquito prevalance on impounded and ditched salt marshes, Assawoman Wildlife Area, Delaware, 1956. In 1974 F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. University o- Delaware. 80 pp. Clark, J. 1974. Coastal Ecosystems. The Conservation Foundation. Washington, D. C. 178 pp. Cockran, W. S. 1938. New developments in mosquito control in Delaware. In 1974 F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. Universityof Delaware. 80 pp. Connell, W. N. 1940. Tidal inundation as a factor uniting distribution of Aedes spp. on a Delaware salt marsh. In 1974 F. C. Daiber. Tide Marsh Ecology and Wildlife. CMS. UniversitTyof Delaware. 80 pp. Cottam, C. and W. S. Bourn. 1952. Coastal marshes adversely affected by drainage and drought. Trans. N. Amer. Wildl. Conf. 17: 414-421. Cottam, C., W. S. Bourn, F. C. Bishop, L. L. Williams, Jr., and W. Vogt. 1938. What's wrong with mosquito control? Trans. N. Amer. Wildl. Conf. 3:81-107. Daiber, F. C. 1974. Salt marsh animals. CMS. University of Delaware. 86 pp. Dukes J. C T D. Edwards, R C. Axtel] 1974. Distributipn of larval faanlae (Dipteral in a partina alternilTora salt marsn. a. 5. nt. 11(1); 79-83. Ferrigno, F. 1961. Variations in mosquito-wildlife associations on coastal marshes. In 1974 F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. Universityof Delaware. 80 pp. Ferringo, F. and D. M. Jobbins. 1968. Open marsh water management. In 1974, F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. University of Delaware. 80 pp. Florschutz, O. 1959. Mosquito production and wildlife usage in impounded, ditched, and unditched tidal marshes at Assawoman. Wildlife Area, Delaware. Proc. J. J. Mosq. Exterm. Association. 46: 103-111. 204 Hansens, E. J. 1949. The biting fly problem in New Jersey resorts and its relation to mosquito control. Proc. N. J. Mosq. Exterm. Assoc. 36: 126-130. Headlee, T. J. 1939. Relation of mosquito control to wildlife. In 1974, F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. UniversiTy of Delaware. 80 pp. Lesser, C. 1975. Some effects of grid system mosquito control ditching on salt marsh biota in Delaware. Master's Thesis. University of Delaware. 25 pp. Nealy, W. W4. 1962. Saline soils and brackish waters in management of wildlife, fish and shrimp. In 1974, F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. University oT-Delaware. 80 pp. Price, M. H. 1938. New developments in mosquito control in Rhode Island. In 1974, F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. University of Delaware. 80 pp. Rockel, E. G. 1969. A marsh physiography influence on distribution of intertidal organisms. Proc. N. J. Mosq. Exterm. Assoc. 56: 102-115. Stearns, L. A., D. MacCreary, and F. C. Daigh. 1939. Water and plant requirements of the muskrat on a Delaware tide water marsh. In 1974, F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. University of Delaware. 80 pp. Stearns, L. A., D. MacCreary, and F. C. Daigh. 1940. Effects of ditching on the muskrat population of a Delaware tidewater marsh. In 1974, F. C. Daiber, Tide Marsh Ecology and Wildlife. CMS. University of Delaware. 80 pp. Stewart, R. E. 1951. Clapper rail populations of the Middle-Atlantic states Trans. N. Amer. Wildl. Conf. 16: 421-430. WASTE DISPOSAL Waste disposal represents a considerable threat to the maintenance of a healthy estuarine environment. The quantities of solid and liquid waste that must be disposed of through planned programs is increasing daily at a rate far surpassing that of population growth. The production of packaging materials, for instance, a principle component of solid waste, has risen over 100 per cent since 1958 to an estimated 147 billion pounds in 1976. Other components of waste include garbage, construction waste, used appliances, municipal sewage and 205 industrial wastes. Solid Waste Disposal Traditionally, the cheapest, most expedient methods for disposing of solid waste have been exercised. In cities and municipalities bordering estuaries, wetlands or lands bordering wetlands (and sometimes the estuary itself) have often been used for locating solid waste dumps as well as sanitary landfills. This result is based an the generally accepted but antiquated notion that the wetlands are not of direct benefit to man unless "reclaimed" by man (Metzgar, 1973) (see Wetlands and Estuarine Productivity). Since wetlands are also generally located away from people, dumping in them did not seem to perceivably hurt the aethetics of a town dweller. Depositing wastes in this manner destroys productivity of the estuarine fringe where the solids are most frequently dumped. Secondly, improper waste disposal on or near the wetlands surface leads to groundwater pollution as water enters the waste and saturates the refuse. The consequence is a highly polluted, maloderous leachate. It has been found that continuous leaching of an acre-foot of sanitary landfill produces a minimum extraction of 1.5 tons of sodium, 1.5 tons of potassium, 1.0 ton of calcium, 1.0 ton of magnesium, 0.9 ton of chloride, 0.2 ton of sulfate and 3.9 tons of bicarbonate, in less than one year (California State Pollution Control Board, 1954). In Delaware, as in many coastal states, illicit dumping on wetlands is a common occurrence. However, there is also a great deal of community sanctioned disposal that eventually ends up on wetlands or in the estuary. For example, between 1960 and 1968 an old gravel pit in New Castle County, the Llangollen Landfill, was used to dump municipal and industrial refuse (Apgar, 1975). The landfill, approximately sixty acres in size, was dug well below the groundwater 206 table to the Potomac formation. The fact that excavation reached the Potomac sands and silts is critical, for the Potomac formation forms the most productive groundwater system in the county. As time passed, water percolated through the poorly packed and covered landfill, producing a highly contaminated leachate which eventually filtered through to the Potomac sands. By 1972, the contaminated groundwater was being pumped by domestic wells and two private water concerns. Test wells drilled by the county confirmed that leachate from the landfill was indeed contaminating the aquifer. Corrective measures to date include recovery wells to pump the polluted leachate out of the aquifer. However, the recovery wells were then faced with a disposal problem of their own: what to do with the leachate? Unfortunately, Army Creek, which runs near the Llangollern Landfill and eventually into the Delaware River, was used as a convenient receptacle. Needless to say, the biota of Army Creek (and probably in the Delaware estuary) has suffered (Simek, personal communication). The solution to the Llangollen Landfill problem is complicated. Here, a solid waste problem has evolved into a solid and liquid-waste problem--one that will take millions of dollars to correct (Simek, personal communication). The leachate is difficult to treat due to the dissolved organic compounds. The contaminated aquifer is spreading even though recovery wells -are in operation. It is unfortunate that the estuary must again suffer because of lack of informed decision making and foresight. But, it is the estuary that usually does suffer because of its size and ability to carry away and dilute point source pollution. Yet the pollution, although flushed from the point and diluted, still ends up somewhere downstream creating a deleterious impacAt alojig~~.ts entire journey. Since landfills are prone to leaching, it is advisable to locate them away from large aquifers and away from wetlands and watercourses. This will 207 help to avoid unfortunate incidents as at the Lilangollen Landfill. Dumping solid wastes on the surface of wetlands or on areas which drain into wetlands also will introduce dissolved solid waste compounds into the water. Creating potable waters from waters fouled by toxic materials is extremely difficult and economically unrealistic. Landfills when managed properly, can provide an inexpensive convenient means of disposing of solid wastes. Yet, as the volume of solid waste increases, land suitable for use as landfills decreases, especially in populated centers along -the East Coast. Reducing the quantity of solid waste would help to minimize the waste disposal problem, as would preparing the waste by: supercompaction, to reduce the volume of waste; digesting garbage to reduce its quantity (producing a humus material and natural gas); or incineration, under controlled conditions (to prevent air pollution) to reduce the amount of solid waste. Alternative uses of solid waste include creating artificial hills; using waste concrete, masonry and rock for artificial reefs; and making building bricks from compacted solid waste. Since land suitable for solid waste disposal in urban areas is limited, alternative sites are difficult to locate (National Estuary Study, 1970). Finally, when planning for solid waste sites in the coastal zone it is of utmost importance to: 1. Locate landfills not on or near wetlands but far enough away from wetlands and watercourses to avoid water pollution. 2. Locate landfills to avoid significant disruption of normal drainage patterns (Clark, 1974). Liquid Waste Disposal The discharge of liquid wastes into estuaries poses a larger problem than that of solid waste disposal. As was shown with the Llangollen Landfill example, 208 solid waste problems can degenerate into liquid waste problems. Similarly, estuaries, and riversleading to estuaries, have traditionally been used to dispose of liquid wastes. The magnitude of the liquid waste problem has, in the last several decades, proliferated to the point where at least 100 industrial (point source) discharges are made into Delaware's tidal creeks and bays. Liquid wastes from municipal and industrial point sources have six types of impacts which tend to restrict other uses in the estuarine zone (NEPS, 1969); (1) floating or settleable materials are unpleasant to look at or destroy the bottom community of organisms; (2) toxic materials destroy living organisms directly or damage their reproduction or poison their food supply; (3) organic wastes decrease the dissolved oxygen necessary for aquatic life; (4) excessive nutrients cause proliferation of some ecosystem components (as algae) and cause adverse effects in others; (5) pathogens (germs, disease) cause public health hazards; (6) heated wastes reduce dissolved oxygen and cause other adverse effects (NEPS, 1969). These impacts generally can be managed through proper treatment systems. Non-point source wastes including fertilizers, pesticides, runoff from streets and highways, right of ways, feed lots and farms, cultivated and irrigated fields, and accidental spills, are harder to manage. More effective controls and educating people to become aware of their activities would help to alleviate some of these problems. Enforcement of water quality standards would also lead to improvements. Since the component of any liquid waste can vary widely (organic compounds, heavy metals, pesticides, etc.), as can the volume and concentration of waste, and the length of time the discharge is made, it is difficult to miake blanket recommnendations. Each point source discharge must be analyzed individually to determine the potential harm to the ecosystem. In general, almost all liquid wastes need some sort of treatment before discharge. Proper land use and water 209 Figure 68 Solid Waste Disposal Little Creek Wildlife Area Figure 69 Solid Waste Disposal and Bulkhead Indian River Inlet 210 quality planning and management can address many of these problems but public awareness is essential to assure recognition of the true value of the wetlands and estuaries. References Apgar, M. 1975. We can't afford to let this happen again. Delaware Conservationist XIX(2): 19-21. Clark, J. 1974. Coastal ecosystems. The Conservation Foundation, Washington, D. C. 178 pp. Simek, E. (personal communication) Roy Weston and Associates, West Chester, Pennsylvania. The National Estuarine Pollution Study. 1969. U. S. Department of Interior. FWPCA. Volume II. 575 pp. National Estuary Study. 1970. U. S. Department of Interior. U. S. Government Printing Office, Washington, D. C. Volume II. 303 pp. Metzgar, R. G. 1973. Wetlands in Maryland. Maryland Department of State Planning, Baltimore, Maryland. Publ. #157. California State Pollution Control Board. 1954. In: J. Clark. Coastal Ecosystems. The Conservation Foundation, Wasli~ngton, D. C. 170 pp. RESIDENTIAL, COMMERCIAL AND INDUSTRIAL DEVELOPMENT The spread of municipalities and industries into the wetlands areas has led to a substantial decrease in the acreage of wetland systems. In the last thirty years, at least 4,300 acres of the marshes and wetlands of Delaware have been lost directly to residential, commercial and industrial development (Daiber, et al., 1975). With the pressures to expand the use of coastal zone areas increasing, the possibilities for new losses grow each year. Historically, coastal areas have been developed because of the food resources they can provide for developing human populations and because of the possibilities they presented for solving the waste disposal and transpor- tation problems of cities and industries. Today, besides these traditional uses of coastal areas, waterfront property is being heavily developed for 211 recreational purposes (Metzgar, 1974). The building of trailer parks, marinas and motels is increasing to support the expanded use of our coastal areas in hunting, fishing, swimming and boating activities. Wetlands development can affect the coastal areas in many ways, the most obvious of which is the destruction of the physical habitat due to dredging and filling operations (refer to Dredging and Spoil Disposal). Development and site preparation practices also lead to other severe ecological problems. Surface water runoff and circulation patterns of wetlands and estuaries are usually upset during wetland manipulations resulting in unnatural erosion and siltation. For example, erosion of land cleared of vegetation for development can be increased ten times over that of areas retaining their natural vegetation (Oostdam, 1971). Municipalities and industries produce large amounts of waste materials that are often introduced into wetlands water systems. Delawareans produce, through their municipalities and industries, almost 1,000,000 tons of solid waste material each year, much of which ends up on refuse dumps created in or near wetlands areas such as Llangollen Landfill (Delaware Statistical Abstract, 1975) (See Waste Disposal). Besides the solid wastes produced, industries and cities create liquid waste effluents that are often discharged into our waterways. It is estimated that 30 per cent of the suspended sediment load of the Delaware River Estuary is due directly to industrial and sanitary sewer discharges (Hartzell, 19639; Wicker, 1955). Some of this material Presents a problem simply because it increases the turbidity of our streams and rivers; other effluents are toxic to estuarine organisms. Both lead to increasing ecological problems associated with residential and commercial development. The degree of impact of each operation varies greatly depending on the kind of development being undertaken, the degree of landscape and drainage pattern alterations occurring, the density of the individual development projects, the proximity of the operation to the water and the basic ecologic 212 sensitivity of the area (Clark, 1974). Ecologic sensitivity is a topic that researchers are now trying to assess more precisely for each particular wetland area of Delaware. Each area has a unique ecological character and some areas are more vulnerable to disruptions than others. Since there will always be some development occurring in the coastal zone areas, it is important that the more sensitive areas be identified and development in these areas be kept to a minimum. Any development in the wetland zones or in areas contiguous to wetlands usually involves the clearing of land and the exposing of bare soil for some time. As a result, an artificially high load of sediment is introduced into watercoursesas a consequence of erosion from the exposed soil. Natural vege- tation decreases erosion by retarding the flow of water over the ground surface. It also allows water to percolate down into the soil thereby increasing ground- water supplies. A naturally vegetated area contributes about .1-2.5 tons of sediment per acre per year to the creeks and rivers it borders. This figure increases to 2.3-9.2 tons per acre per year in areas that have been cleared of vegetation for development (Oostdam, 1971). When the vegetation is removed, the flow of water across the surface is facilitated, percolation is decreased and erosion of soil increased. Considering all construction projects in the United States, this means approximately 48,000 tons of additional sediments are deposited in our water systems for each square mile undergoing construction each year (Midwest Res. Inst., 1973). When the areas under construction become surfaced with roadways and parking lots, the sediment problems may diminish, but other problems associated with water flow arise. Surface water runoff from urban areas has become a major source of toxic substances common to the waterways. Surface waters pick up toxic substances from street litter, yard refuse, septic tanks, motor vehicle 213 drippings, garbage dumps, stagnant waters and pesticide residues (Clark, 1974). Waste materials associated with the ground surfaces of industrial sites also add exotic toxins to the surface water runoff. Impervious surfaces, then, increase the amount of toxic surface water runoff. In addition, the natural processes of purification by filtration, absorption, deposition, and oxidative breakdown of pollutants by plants and microorganisms in the soil, is short circuited. Runoff from streets and parking lots with the associated load of toxic material is fed directly through storm drainage and canalizations to creek beds which eventually feed into the estuarine system. The effects of runoff can be reduced somewhat if development is tailored to the individual characteristics of each area -- climate, topography, soil conditions and vegetative cover. Final grading of the area can be accomplished to facilitate proper drainage by imitating the natural drainage patterns as closely as possible. The exposure time of bare soil should also be kept to a minimum to reduce erosion, and maximum amounts of vegetation should be included in the final development plan to reduce problems associated with large amounts of surface water runoff. Where runoff is created, it should not be allowed to flow directly into the natural water shed for it often contains ecologically harmful materials and unnatural silt loads that stress both plants and animals. Finally, all types of sewage and surface drainage systems should be kept separate so that the material each contains-domestic sewage, urban toxicants and industrial wastes - can receive the special treatment each needs to render it harmless to the environment. Since population increases have been forecast for many of Delaware's coastal areas, the problem of domestic sewage disposal becomes a critical one in all types of residential areas. Sewage poses a problem because it contains large amounts of phosphorous and nitrogen compounds and, often, pathogenic 214 materials. Large amounts of phosphorus and nitrogen can promote eutrophication in natural systems thereby reducing the health of the biotic communities. Further, people can often be exposed to the pathogenic substances and the illnesses they cause by swimming in waters receiving sewage effluent or by eating estuarine organisms that live in or near sewage discharge areas. Septic tanks are not always effective in coastal systems because coastal soils often do not have the proper drainage and absorptive properties to render spetic tank effluents harmless. Large centralized systems appear more logical but these also have many problems that have to be overcome. Sewage treatment plants attempt to remove the phosphorus, nitrogen and pathogenic materials but are not always completely successful. Most of Delaware's sewage plants have only secondary treatment capabilities which remove only one-half of the phosphates and nitrates. The amount left in the sewage is still enough to cause eutrophication, increased bacterial growth, high BOO levels and low dissolved oxygen levels in coastal waters. Large treatment plants also have special problems simply because they handle such large amounts of sewage. If breakdowns or overflows of the system occur, catastrophic pollutiona] problems could result due to the consequent introduction of large amounts of sewage into discharge areas. The most effective means of reducing the problems associated with large treatment facilities would be to eliminate them from wetlands areas completely. While this might be the most effective means, it is not always going to be the most practical. If treatment facilities must be concentrated in coastal areas their problems can be minimized by implementing some sound management practices. These include: (1) having several small capacity plants instead of one large treatment facility thereby distributing the sewage load and reducing the possibility of a major, catastrophic pollution event; (2) having separate sewer 215 drainage and storm drainage systems since plant overflows are often caused by large amounts of storm runoff; (3) keeping industrial and domestic water separate because of the different treatment processes each require, and (4) trying to develop treatment beyond the secondary stage either by utilizing land areas to handle the final breakdown processes through natural means or by developing tertiary treatment facilities in the individual sewage treatment plants (Clark, 1974). One area of the state that is experiencing a great amount of residential development and, hence, is faced with many of the problems associated with residential areas, is that surrounding the small bays of Sussex County (Daiber, et al., 1972, 1974, 1975). Little Assawoman, Rehoboth and Indian River Bays attract much residential waterfront development because they are more protected than is the open coastline adjacent to the ocean, and because they offer much in the way of water recreation. The problems arise because these bays are relatively shallow and have fairly restricted openings to the ocean for water exchange (Aurand, 1974). In essence, the small bays have a very slow flushing rate and therefore, pollutants tend to become trapped in the bay system, rather than being flushed to the ocean. The most commion type of residential development in these bay areas involves the lagoon concept of wetlands dredging and filling (Daiber, et al., 1972, 1974, 1975, Aurand, 1974). Lagoon development typically involves dredging canals into shore zone and marsh areas with the spoil created being deposited in the marsh to raise the surface level of the undredged areas. Houses are then constructed on these interlagoonal areas or mobile homes installed, and the lagoons (or canals) serve to provide dock space for the residents. From the point of view of the developer, it is easy to see why this method is so attractive; it is a fairly inexpensive way of stabilizing land and greatly increases the availability of waterfront property. 216 As concerns the ecosystem, however, the lagoonal type development can often cause serious problems. The wetlands areas consumed by the development are lost to the larger estuarine ecosystems and so the resource base on which the estuary depends is reduced. Further, most lagoons are constructed with only one opening into the bay to which they are adjacent and this has been found to seriously hinder water circulation (Daiber, et al., 1972, 1974, 1975). Complete flushing of the lagoons is rare and water in the lagoons often becomes stagnant and unable to support a rich biotic community. This is especially true in some of the older lagoon systems like those adjacent to Little Assawoman Bay which, at certain times of the year, show diminished benthic and fish populations. The absence of organisms is thought to result from very low oxygen levels that often occur in the lagoons due to poor circulation. Some of the ecologic problems associated with the lagoon developments are being corrected by the Wetlands Act legislation. For instance, it has been proposed that no dead end lagoons be constructed in Delaware (for other proposed regulations see DNREC, Proposed Wetland Regulations, Division of Environmental Control, January 19, 1976). There are also other lagoon associated problems that arise from having high concentrations of people living in a relatively small area occupied by each one of these developments. Any residential area must contend with the problems of sewage disposal and urban runoff, but these might be especially intensified in the small bays areas. The density of people inhabitating these communities is often high during the summer when water systems are most naturally stressed, and the increased demands placed on these systems at these times could be critical. Most of the mobile home parks surrounding these bays utilize septic tank disposal systems because they are the most inexpensive and easiest systems to 217 Figure 70 Land Use Change Masseys Landing Area 1938 218 Figure 71 A~~~~~~~~A Land Use Change Masseys Landing Area 1954 219 Figure 72 Land Use Change Masseys Landing Area 1973 220 Figure 73 Dredge Lagoon and Mobile Home Development White Creek 221 develop rapidly. They are not the most effective, however, in keeping untreated sewage from reaching estuarine waters. Considering the populations that lagoon communities contain and the proximity of these communities to the water, the problem of septic tank overflows reaching the small bays is a serious one. Further, since most people purchase property in lagoon communities because they own boats, the problems associated with large concentrations of power craft in one area - the additions of large amounts of oil and gas to the water - also increase greatly (see Marinas discussion also). Similar complications arise with each of the many industries located in the coastal zone area of Delaware. Over 100 industrial plants are located along the Delaware River and the tidal creeks that drain into it (DNREC Water Quality Inventory, 1975; University of Pennsylvania Department of Landscape Arch. and Reg. Plan., Fall 1966/1967). To this list must be added the number of industries located in Pennsylvania and New Jersey that also discharge waste effluents into the Delaware River Estuary. All of the problems associated with residential areas also exist in one form or another in industrially developed areas. The physical presence of the plant in the coastal zone often represents lost wetlands areas, and frequently has effects on natural drainage, runoff and circulation patterns occurring in the surrounding wetlands sections. As with urbanized areas, surface runoff in industrial areas often picks up toxic wastes and carries them directly to the estuary resulting in many areas of the Delaware River experiencing high industrial pollutant loads. The problems existing in the individual tidal creeks (e.g., Broadkill River) have also been partially correlated to the practices of the industries bordering them (Au rand, 1968). The problems associated with residential, commercial and industrial develop- ment would be easier to overcome if industries and cities did not occur so 222 closely together. They pose similar problems which must be handled in similar fashion. But the specifics of each development and its problems are wide- ranging enough to cause general solutions to be fairly ineffective. Since most areas of the state are projected to experience growth in both residential and industrial directions,it appears that the problems arising from both will continue to confront planners simultaneously. References Aurand, D. 1968. Seasonal and spatial distribution of nitrite and nitrate in surface waters of two Delaware marshes. Master's Thesis, University of Delaware. 140 pp. Aurand, D. 1974. "The Delaware Study", in Ruth Mathes, ed., Canals and Waterfront Development, Conference Summary, sponsored by Central Atlantic Environment Center, Salisbury State College, October 27, 1973. pp. 11-14. Clark, J. 1974. Coastal Ecosystems. The Conservation Foundation, Washington, D. C. Daiber, F. C., D. Aurand, W. Bailey, R. Feldheim, and K. Theis. 1972. The environmental impact of dredge and fill operations in tidal wetlands upon fisheries biology in Delaware. 1972-73 Report to Division of Fish and Wildlife, Department of Natural Resources and Environmental Control, State of Delaware, Dover. 98 pp. Daiber, F. C., D. Aurand, W. Bailey, and G. Brenum. 1974. Ecological effects upon estuaries resulting from lagoon construction, dredging, filling and bulkheading. 1973-74 Report to Division of Fish and Wildlife, Department of Natural Resources and Environmental Contro, State of Delaware, Dover. 80 + XLIV pp. Daiber, F. C., D. Aurand, G. Brenum, and R. Clarke. 1975. Ecological effects upon estuaries resulting from lagoon construction,dredging,fillinq and bulkheadinq. Report of Division of Fish and Wildlife, State of Delaware. Project F-25-R-2. 197 pp. Daiber, F. C., L. L. Thornton, K. Bolster, and 0. Crichton. 1975. Delaware Wetlands Atlas: Phase I. College of Marine Studies, University of Delaware. Delaware 1975 State Water Ouality Inventory. Prepared for the Governor by the Department of Natural Resources. Division of Environmental Control. N. C. Vasuki Project Hanager and Co-author; James L. Pase Project Director and Author. 151 pp. Delaware Statistical Abstract. 1975. Prepared by the Social and Economic Analysis Section, Delaware State Planning Office. 233 pp. 223 "The Delaware River Basin. A Preliminary Inventory of Natural and Cultural Conditions", Department of Landscape Architecture and Regional Planning, University of Pennsylvania, Fall 1966/1967. Department of Natural Resources and Environmental Control. January 19, 1976. Proposed Wetlands Regulations. Division of Environmental Control. 21 pp. Hartzell, E. P. 1969. Disposal of shoal material from the dredging operation in the Delaware River: Preliminary Report, special studies section U. S. Army Engineer District, Philadelphia, Pennsylvania. 16 pp. In Oostdam. Metzqar, R. S. 1973. Wetlands in Maryland. Maryland Department of State Planning. Annapolis, Maryland. Pub. No. 157. Midwest Research Inst. 1973. Draft Report - Methods for identifying and evaluating the nature and extent of non-point sources of pollutants EPA Contract No. 68-01-1839. Midwest Res. Inst. Oostdan, B. L. 1971. Suspended Sediment Transport in Delaware Bay. Ph.D. Dissertation. University of Delaware. 316 pp. Wicker, C. F. 1955. The prototype and model Delaware Estuary. AIHR Computes- rendu de la sixieme Assemblee Generale La Haye 1955. Vol. 1. pp. A12-1-A12-18. In Oostdam. MARINAS Marinas are facilities on the waterfront that provide launching, mooring, docking and repair facilities for recreational and commercial boats. Marinas are typically located in good harbors near population centers. Although originally boatyards for commercial fishermen, marinas now receive most of their business from pleasure boaters. The great increase in the number of pleasure boats has created a high demand for marinas with their mooring space and service facilities (Metzgar, 1973). The increased demand for marinas and other recreation-based developments can be traced to several factors. These include (National Estuarine Pollution Study, 1970): 1. the growth of the total population, 2. the concentration of the population in urban coastal environs, 224 3. the changing characteristics of the population (increased disposable income, employment, etc.), 4. the increase in leisure time and decrease in the work week, 5. the increased mobility of the population. These factors create an ever increasing demand for outdoor recreation. The usage of seashore parks in Delaware, for instance, has risen dramatically in recent years. From 1966 to 1974 the number of people visiting Cape Henlopen Park and the Delaware Seashore Park rose 378 per cent (see Table 4) even thouqh a user tax was initiated in 1972. (Statistical Abstract, 1975) Similarly, Delaware is experiencing a rise in boating activity (see Table 5). The demand for marinas and the services and facilities they provide increases concomitantly with the ever-increasing usage of the coastal zone. The increased demand for marinas is putting pressure on the wetlands for marina development. Wetlands property is a desirable location because it has typically been less expensive, more contiguous to natural harbor areas than uplands, and because it is relatively easy to dredge and manipulate. In addition, since the physical size of harbors is generally not large, marinas are usually limited in size and consequently the increased interest in boating demands that new marinas be constructed. Suitable wetland areas that are accessible by boats are, then, constantly in demand. It is now becoming evident, however, that the area of shoreline available for development is fairly limited. Most of the shore is already either privately owned, restricted by government and state facilities and sanctuaries, inaccessible to large portions of the population, or already developed (see Tables 6 and 7). Still, until recently many acres of wetlands were annually being consumed to fill t6he demand for wetlands-based activities as marina construction. While wetlands seem very suitable for marina development, many marina- oriented problems arise. The major impact of a marina on tidal wetlands is in 225 TABLE 4 TOTAL ATTENDANCE AT THE FIVE STATE PARKS' IN THE COASTAL ZONE (1965-1970) 4000- 3500- 5 E. ,3000- "iG 2500- o > 2000 - 1500 - 0 ,ooo1':'. ''" t 1965 1966 1967 1968 1969 1970 CALENDAR YEARS 1LUMS POND, FORT DELAWARE, CAPE HENLOPEN, DELAWARE SEASHORE,ANU HOLTS LANDING STATE PARKS SOURCE: DELAWARE STATE PLANNING OFFICE TABLE 5 Sales of Boat Licenses in Delaware (1962-1970) Fiscal Year Cash Received1 Number of Boats Registered 1962 $28,924 8,974 1963 30,898 9,538 1964 31,922 9,788 1965 33,371 10,230 1966 35,148 10,818 1967 38,514 11,815 1968 43,076 13,181 1969 49,125 14,941 1970 50,344 15,908 1Licenses for new boats cost $3.CO; boat transfers made as the result of a sale cost the new owner $2.00. Source: Files of the Department of Natural Resources and Environmental Control, State of Delaware, Dover, Delaware. 226 TABLE 6 Land Ownership in Delaware's Coastal Zone (1970) Percent Percent Percent Property Along the... Private Public Restricted Control Control1 Military Delaware River 83 17 0 Chesapeake and Delaware Canal 0 100 0 Delaware Bay 60 40 0 Atlantic Ocean 44 50 6 Inland Bays 92 8 0 1Parks, reservations and wildlife areas. Source: Files of the Department of Natural Resources and Environmental Control, State of Delaware, Dover, Delaware. TABLE 7 Development of Delaware's Little Bays (1938-1969) Percent of Shoreline Developed1 Bay and Length of Shoreline 1938 1969 Rehoboth Bay: 48 miles less than 1 25 Indian River Bay: 45 miles 9 44 Little Assawoman Bay: 27 miles less than 1 10 1Mostly summer residences. Source: Environmental study of Rehoboth, Indian River and Assawoman Bays, 1969. Delaware State Planning Office, Dover, Delaware. 227 the area of biological productivity and water quality control. Construction of marinas almost always involves dredging, bulkheading, and spoil disposal; consequently, the problems associated with these activities must be considered, (see discussions of these subjects). Problems associated with dredging include: 1. the physical destruction of wetland habitat, 2. the introduction of new circulation patterns which changes salinity profiles, tidal amplitude and flushing characteristics, 3. potential interference and pollution of freshwater aquifers with saltwater (refer to Dredging for more detail). Effects of filling and spoil disposal include: 1. the deposition of spoil on wetlands (filling) destroying the vegetation, production and overall ecological value of the wetland as an ecologic entity, 2. the deposition of spoil in estuarine waters increasing the concentration of suspended sediments which can cause mortalities in fish, invertebrates and plankton, 3. the deposition of spoil on the bottom which can cause mortalities in the invertebrate bottom communities as they become covered with spoil (refer to Spoil Disposal). Marinas tend to be constructed in the form of dead end lagoons, therefore problems associated with dredged lagoons often appear, including: 1. altered circulation patterns and a general decrease in flushing rate, 2. stratification in terms of salinity, temperature and dissolved oxygen leaching to poor water quality in the bottom of lagoons, 3. periodic fish kills and the exclusion of oxygen consuming benthic organisms in the lagoon, 4. the construction of bulkheads which destroy nutrient exchange between marsh banks and the water column (refer to Dredging). 228 Also the building of marinas in a wetlands area tends to increase the demand of adjoining wetlands and uplands for development of associated businesses (restaurants, motels, shopping areas, boat storage, sale and repair facilities). Some impacts associated with subsidiary development include: 1. possible alteration of wetlands, 2. the increased runoff from cleared uplands causing increase of suspended sediment and the introduction of pollutants as pesticide residues into estuarine waters, 3. introduction of solid and liquid point source wastes (sewage, chemical wastes, etc.) to estuarine waters from municipal, commercial and industrial sources, 4. introduction of exotic toxic materials associated with human habitation from runoff, as car drippings, yard refuse, septic tank leachate, stagnant waters (refer to Residential, Commercial and Industrial Development). Discharge of sewage from vessels represents a dramatic source of pollution to marinas and to enclosed bays such as the small bays in Sussex County. For instance (Giannino, 1974):' 1. there are eight million recreational watercraft using navigable waters in the United States, 2. estimates are that 1.3 million recreational watercraft are toilet equipped and discharge sewage into United States waters, 3. recreational watercraft tend to discharge during peak water contact sport uses, creating health and esthetic hazards, 4. the trend in recreational watercraft is to install on-board toilet facilities, 5. sewage discharge can contain pathenogenic organisms that cause diseases as dysentery, typhoid, gastroenteritus and infectious hepatitis. 229 This means that marinas must incorporate sewage pollution control systems that are equipped to hold and dispose of sewage in a manner coimmensurate with state and federal standards and in a way which proves harmless to the ecosystem. Oil and fuel spillage from inefficient marine engines and as a result of spills from transfer processes, often enters the water. This represents another source of pollution. Heavy boat traffic causes increased erosion to the mud banks typical of a marsh. Banks covered with cordgrass, Spartina alterniflora, are capable of resisting erosion, but even they are vulnerable to the aggravated erosion resulting from excessive boat wakes (Mann, 1974). These vulnerable edges should be identified and considered when locating a marina. Marinas need not be biological wastelands. Submerged pilings can support a wide variety of organisms including bryozoans, algae, amphipods, mussels, barnacles, sponges and tunicates provided water quality is good. Such communities can support forage fishes (which are consumed by many species of game fish, waterfowl, and wading birds) as well as a variety of juvenile sport fishes. Controlling water quality by avoiding spillaqe of fuels, discharge of sewage and poor circulation can promote plankton growth which greatly increases the primary productivity of the area. Thus, a well planned marina can promote and support biological life and contribute to the productivity of the area. In conclusion, a marina which is placed on or near wetlands should have good circulation through the marina by flushing every tidal period, strict sewage pollution control, and adequate water/structural contact area to promote growth of organisms and encourage biological productivity. Spoil should be used to create new marsh where possible, or placed on uplands away from the wetlands. The marina should maintain biological production equal to that which was lost. 230 Figure 74 Marina White Creek Figure 75 Marina Dewey Beach 231 Recommendations 1. As little wetlands as possible (preferably none) should be altered when constructing marinas. 2. Harbors with poor circulation should be avoided for marinas. 3. Support facilities should be built on uplands. 4. When dredging, follow recommendations listed in the "dredging" section of report. S. Gently sloping sides of rock or earth instead of bulkheading should be used wherever possible so as to promote the growth of an attached marine community (barnacles, algae) or marsh cordgrass respectively (Giannino, 1974). 6. Pilings rather than solid fill should be used to elevate marine structures such as docks, piers and walkways. 7. Surfacing of large areas should be minimized where possible and adequate storm drainage installed. 8. Pump-out facilities for boat sewage must be provided. Adequate sewerage treatment facilities must be built on uplands. 9. Ensure against oil and fuel spillage through the use of proper fuel handling techniques and adherance to Coast Guard Regulations (Clark, 1974). References Clark, J. 1974. Coastal ecosystems. The Conservation Foundation, Washington, D. C. 178 pp. Delaware State Planning Office. 1975. Delaware Statistical Abstract. Social and Economic Analysis Section, Dover, Delaware. Giannino, S. P. 1974. Engineering Guidelines for Marinas in Tidal Marshes. Master's thesis. University of Delaware. 105 pp. Mann, R. Assoc. 1974. Recreational boating impact--Chesapeake and Chincoteague Bays. Part 1: Boat capacity planning system. Report for the Coastal Zone Management Program, State of Maryland. 232 Metzgar, R. G. 1973. Wetlands in Maryland. Report for Department of State Planning. State of Maryland. The Governor's Task Force on Marine and Coastal Affairs. 1972. The Coastal Zone of Delaware. College of Marine Studies, Newark, Delaware. United States Congress, Report by the Secretary of the Interior. 1970. The National Estuarine Pollution Study. Washington, D. C., U. S. Government Printing Office. United States Department of the Interior, Federal Water Pollution Control Administration. 1967. Waste from Watercraft. In: S.P. Giannino. 1974. Engineering Guidelines for Marinas in Tidal Mars'R-es, Master's thesis. University of Delaware. 105 pp. AGRICULTURE High agricultural productivity depends not only upon energy subsidy but on good land and adequate subsurface drainage. In Delaware, the natural drainage capacity of the soil is poor,consequently,projects to improve cropland drainage by ditching are common. Because farms border most of the wetland areas in Delaware, much of the fertilizers and pesticides used on the farms end up in the wetlands or the estuaries. Thus, modern agriculture can pollute wetlands and estuaries. Pollution from agricultural sources can occur in three basic ways: 1) high turbidity and sedimentation due to erosion; 2) eutrophication, (the addition of nutrients into the water), and 3) toxicity, due to pesticides. Sediments Turbidity and sedimentation in watercourses are caused in part by surface waters running over fallow or tilled soil. Since there is little vegetation to Inhibit the flow of water and give it time to percolate into the soil, the surface water tends to move rapidly across exposed soil, picking up particles as it moves. These particles are then carried into watercourses. (Creeks, tidal creeks, bays, etc.) In general, it has been determined that surface water erosion from pasture yields .3-1.9 tons per acre per year of sediment, cropland 233 FIGURE 76 SUSPENDED SEDIMENT CONCENTRATION MAP KEYfrmfn 0 -5"4(_r~~~~~w linear regression. mg/l1iter &~~~~~~~~ ~~~~~~ v 211 5.6 (D SWD 66rov 104 7.7 -~~~~~~~~~~~3 unc lass ified Doll/r,2 0 - -----------~~~~~0 10 Nautical Miles Source: Kiemas Et Al 1974 234 2.3-9.2 tons per acre per year, as opposed to woodlands .1-2.5 tons per acre per year. In total, it is estimated that cropland contributes 45 per cent of all the sediment load in watercourses in the United States each year. Thus, water- courses (creeks, tidal creeks, bays, etc.) bordering large drainage areas of pastures and croplands are prone to perturbations due to suspended sediments. Generally, estuarine organisms are relatively tolerant of high concen- trations of suspended sediments, however, certain species show adverse effects at relatively low suspended sediment concentrations. It appears from the limited data on suspended sediments in Delaware that the possibility for lethal and sublethal effects on species of vulnerable organisms (for example, oyster larvae and juvenile shad) does exist due to high concentrations of suspended sediments, particularly from the Bombay Hook area north to Wilmington. Agricultural actions which can reduce the impact of sedimentation include: 1. Methods to reduce potential surface water runoff such as contouring. 2. A buffer strip with natural vegetation between watercourses and tilled soil. 3. Maintenance of the natural drainage pattern of the land as much as possible. 4. Marsh and wetlands should not be utilized for agricultural purposes. 5. Reducing the time that land remains exposed (Clark, 1974). Nutrients Much concern is centered around nutrients leaching from fertilizers into the water table, specifically, fertilizers containing nitrogen and phosphorus. These two nutrients are potentially the most dangerous because they are relatively more scarce than most other essential elements required for plant growth. In other words, the relative low amounts of nitrogen and phosphorus in the water 235 act as limiting factors to growth and production. Similarly, these elements must be added to the soils to subsidize high yields. In 1969, over 280 pounds of fertilizer was used for every acre of cropland harvested. Much of this is utilized by the crops, some remains in the soil, and some inevitably ends up in the water table. In general, fertilizers are lost from the soil to water by: water per- colating through the soil and leaching soluble nutrients; washing away of animal wastes, and erosion of the surface soil into drainage systems. Additions of phosphorus and, in particular, nitrogen to fields lead to nutrient enrichment of associated drainage ditches, streams, and river systems. This causes drastic shifts in aquatic communities by promoting growth of exotic and "nuisance" species to the point where bathing becomes disagreeable, unpleasant odors are produced, and in general, the aesthetic appearance is destroyed. These impacts can be reduced by agricultural practices, such as: 1. Selecting appropriate fertilizers and then use according to directions (applied in the correct amounts and in the proper season). 2. Havinq soil tested so that only the types of fertilizers needed are applied. Pesticides The entrance of most pesticides into the waters are of great potential harm to estuarine fauna. Pesticides washed into saltwater become "salted out" as particl es deposited i nto estuarine sediments. The resul t is that a rel atively high concentration of pesticides exists in estuarine systems. There is, then, a reservoir of undesirable material or toxins in areas where freshwater meets saltwater. Unfortunately, many marine animals tend to accumulate these toxic 236 pollutants in their flesh. The resultant effects can be catastrophic, including death of the creature, or the impairment of other functions such as growth, reproduction and mobility. Unfortunately, it appears that the estuarine fauna of Delaware has not suffered greatly from pesticides. None of the concentrations of pesticides found in shellfish in Delaware appears excessive. However, sublethal facets of pesticide poisoning on eggs and larvae of aquatic life (fish, shellfish) and on egg shell secretion in predatory birds, although difficult to impossible to measure, has no doubt added to the burden of the already taxed fauna of the estuary. Although Delaware has suffered little noticeable harm, investigations of potential harm of all kinds of pesticides as well as other chemical and municipal wastes must continue. Disasters in other states and communities are grim reminders, such as the recent contamination of the entire community of Hopewell, Virginia, and parts of the James River by Kepone, a pesticide that was supposed to replace the chlorinated hydrocarbons. Similarly, the discharge of PCB's into the Hudson River has closed large portions of that river to commercial fishing. Massive fish kills have been associated with halogenated hydrocarbons including endrin, dieldrin, DDT and DDE. Endrin, used as a rodentide, is particularly toxic. If bluegills are exposed to six parts per billion of endrin, 50 per cent will die within ninety-six hours. DDT has also been shown to be ex- tremely noxious and through the process of biological magnification, certain estuarine fishes such as mullet and silversides (both common to Delaware) can accumulate up to 1,500 times the amount of DDT present in the water. In 1972, pesticides derived from agricultural sources accounted for the death of approximately 1.5 million fish of a total of 1.8 million fish reported killed due to agricultural practices in the United States (Statistical Abstract, 237 1973). Excess fertilizer and manure-silage runoff accounted for the remainder. In 1969, a peculiarly bad year for fish kills, 6.4 million fish were reported killed as a result of agricultural practices, 5.9 million of which were traced to pesticides. In Delaware, in 1969, only two fish kills were reported, one on the Little River, near Little Creek and one in Silver Lake, Rehoboth Beach. The kill at Little Creek was due to a combination of factors (not stated) and on Silver Lake, excess sewage was the culprit (FWPCA, 1969). Phytoplankton, the basic food supply for all animals in the estuary, (see Wetlands and Estuarine Productivity) are extremely sensitive to herbicides. For instance, low concentrations (.02 ppb) of Monuron, a herbicide, is lethal to five species of phytoplankton commonly utilized by molluscs as food. Similarly, Divron (at .04 ppb) proves lethal to the same five species of phytoplankton. Obviously, minute quantities of certain herbicides are extremely toxic to phytoplankton. Phytoplankton are equally sensitive to chlorinated hydrocarbons such as DDT. Any reduction in phytoplankton is ultimately reflected in the higher trophic levels of crustaceans, molluscs and fishes since phytoplankton form the base of the food chain (see Estuarine Productivity). Inorganic salts such as arsenic have been shown to reduce the standing crop of salt marsh cordgrass (Spartina alterniflora). Pesticides, even in minute quantities, have critical effects on the animals of the marsh-estuarine environment. It is vital that concentrations of toxic chemicals be kept at a minimum. The following is a list of recommendations for the use of pesticides which is applicable to both agricultural and non- agricultural applications: 1. Be certain there is a real need to use the pesticide, and use only those necessary to treat the pests involved (i.e., avoid broad spectrum pesticides to treat limited pests). 238 2. Treat only the minimal area necessary. 3. Select a chemical toxicant that will be least dangerous to fishes. Avoid chemicals that accumulate in the soil. 4. Use only the amount absolutely necessary. Insure no area gets a double dose. 5. Be alert to the composition of the material that carries the pesticide chemical. 6. Plan with care a time for treatment. Avoid migration periods and reproductive periods of fish, shellfish and waterfowl. References Auld, A. and J. A. Schubel. 1974. Effects of suspended sediment on fish eggs and larvae. Chesapeake Bay Institute, Johns Hopkins University. Ref. Number 74-12. Butler, P. A. 1973. Residues in fish, wildlife and estuaries. Rest. Monitoring J. 6(4): 238. Clark, J. 1974. Coastal Ecosystems. The Conservation Foundation, Washington, D. C. Curtis, L. 1969. A three-year survey of the pesticide content of shellfish in Delaware's tidal waters. Mar. Laboratories, University of Delaware. Davis. G. 1976. (personal communication) Federal Water Pollution Control Administration. 1969. Pollution caused fish kills in 1969. U. S. Department of Interior. Washington, D. C. Hartzell, E. P. 1969. Disposal of shoal material from the dredging operation in the Delaware River. In: B. L. Oostdam. 1971. Suspended sediment transport in Delaware BaT. Ph.D. dissertation. University of Delaware. Klemas, V., D. S. Bartlett, W. D. Philpot, G. R. Davis, R. H. Rogers, and L. Reed. 1974. Application of ecological, geological and oceanographic ERTS-1 imagery to Delaware's coastal resources management. CMS-NASA-4-74. Oostdam, B. L. 1971. Suspended sediment transport in Delaware Bay. Ph.D. dissertation. University of Delaware. Sherk, J. A. 1973. Current status of the knowledge of the biological effects of suspended and deposited sediments in Chesapeake Bay region. Ches. Sci. Volume 13: S137-144. 239 Sherk, J. A., J. M. O'Conner, and D. A. Neumann. 1972. Effects of suspended and deposited sediments on estuarine organisms. Phase II. Department of Environmental Research, CBL, Prince Frederick, Maryland. Ref. #72-9E. U. S. Bureau of the Census, Statistical Abstract of the United States: 1974. (95th addition). Washington, D. C., 1974. Wethe, C. 1976. (personal communication) Wicker, L. F. 1955. The prototype and model Delaware estuary. In: B. L. Oostdam. 1971. Suspended sediment transport in Delaware Bay. Ph.D. dissertation. University of Delaware. 240 ENVIRONMENTAL PARAMETERS ENVIRONMENTAL PARAMETERS The following discussions deal with the relationships between estuarine organisms and the various environmental parameters which determine their existence. Understanding of these relationships is essential to proper resource management; especially, as relates to claims of impacts caused by an action, i.e., the secondary effects of an action beyond those immediately experienced at the site. Important environmental parameters in the marine environment are: dissolved oxygen, temperature, turbidity, salinity, tidal flushing and toxic materials. DISSOLVED OXYGEN AND ITS RELATIONSHIP TO ESTUARINE ORGANISMS Free oxygen (02) is required by most of the lower animals and all of the higher animals in the world. Only a relatively few microbes can live without oxygen. Similarly, all plants need free oxygen. The oxygen required by these plants and animals is used to oxidize organic molecules in order to produce the energy required by all living matter. Plants generate more oxygen through photosynthesis than they consume, and are therefore able to support organisms which require oxygen. Over the course of time, the green plants have produced a great reserve of oxygen in the atmosphere of the earth, occupying about 20 per cent of the atmospheric space around the earth. There is a natural balance between processes which produce oxygen (green plants) and processes that consume oxygen (animals and plants). In the aquatic environment, the relative amounts of oxygen are considerably less than in the aerial environment with which humans are familiar. Gases, like oxygen, dissolve into water as a function of their concentration (partial pressure) in the atmosphere. The temperature, salinity and physical properties 241 of the water are also important. Since oxygen occupies one-fifth of the earth's atmosphere, a good bit of oxygen dissolves into our lakes, rivers and oceans. Phytoplankton, which are small floating plants, also contribute oxygen to the waters of the world through their photosynthetic pathways. Since water has a relatively high-holding capacity for oxygen compared to other liquids, a large number of diverse, oxygen-consuming animals have evolved in the hydrosphere. Not all of these organisms require a great deal of oxygen; in fact, many of them have minimal needs. However, the more active, migratory species such as tuna and mackeral, require progressively more and more oxygen to do work and fulfill their metabolic needs. Consequently, they have evolved large gill surface areas in relation to their body size when compared to more sedentary fishes such as the toadfish or summer flounder. Since mackerel and tuna are constantly in motion, oxygen-rich water is continually passing over their gill surfaces. If one of these active fish was put in a relatively small aquarium, where it could not swim; it would probably drown. On the other hand a sedentary toadfish put in a small tank could survive perfectly well. Animals, then, have differing oxygen requirements and have made physiological and behavioral adaptions to meet their particular demands. Although there are, in general, relatively large quantities of oxygen in estuarine waters, these waters are particularly prone to oxygen sags or oxygen depletion. Why are estuarine waters so vulnerable? Principally, estuaries are susceptible to activities perpetrated by man which have the primary impact of decreasing dissolved oxygen levels. Eventually, most of the impact of lower dissolved oxygen in estuaries comes from the introduction of excess organics (including nutrients) from human wastes. Organic material is broken down first by aerobic microbes (small organisms which consume oxygen). In addition the 242 subsequent release of nutrients can lead to uncontrolled growth of algae leading to dense, thick mats of nuisance plant species which obstruct oxygen enrichment pathways from the atmosphere to the water (eutrophication). It must be pointed out that eutrophication in itself is not bad, nor considered "pollution", until it has proceeded to a level where deleterous im- pacts begin. Industrial, municipal and commercial discharqes which contain inorganic and organic wastes can exacerbate eutrophication to undesirable levels causing dissolved oxygen sags in estuaries. Other more localized activities can also decrease dissolved oxygen. Increasing the amounts of suspended sediments (turbidity) causes a severe oxygen demand on the water column. Since much of sediment is detritus (small bits and pieces of organic material), stirring up these particles and exposing them to oxygen in the water column increases the demand for oxygen as microbes increase their activity on the detrital particles (Brown and Clarke, 1968). Also, phytoplankton, which depend on radiant energy passing through the water column to produce oxygen through photosynthesis, are inhibited due to the lack of transmitted light in turbid waters. Turbidity also has the effect of clogging the gill structures of many animals, including fish, which inhibits the C02-02 exchange at the gill surface, consequently asphixiating the animals (Sherk, O'Conner and Newman, 1972). Turbid conditions arise from dredging and spoil disposal runoff from impervious surfaces and runoff from cleared or plowed land. In addition, it has been shown in Delaware, and in other states, that the construction of dredge lagoons (see Dredging) exacerbates stratification of the water column and consequently lowers the dissolved oxygen concentrations at the bottom of lagoons. 243 Although the discussion has so far been limited to man's impact on dissolved oxygen, there are also natural phenomena that tend to utilize and consequently decrease dissolved oxygen levels in estuaries. Foremost, temperature reduces the oxygen holding capacity of water. For instance, at 100C (or 500F) fresh- water has the capability of holding 8.0 milliliters of oxygen per I liter sample. NOTE: Dissolved oxygen is typically expressed in two ways, milligrams per liter (mg/1) and milliliters per liter (ml/1). Milligrams of oxygen per liter is a weight to volume relationship and refers to the total atomic weight of free dissolved oxygen (02) which exists in a I liter sample (1 liter = 1.1 quarts). Milligrams per liter is equivalent to parts per million (ppm). Milliliters of oxygen per liter is a volume to volume relationship. Milliliters of oxygen refers to the actual volume of free dissolved oxygen gas (02) that exists in a one liter sample of water. Conversion factors for the two expressions are as follows: mg/1 x .7 = ml/1 ml/1 x 1.4 = mg/1 At 300C (860F) freshwater can hold only 5.3 ml of oxygen per liter. Similarly, as salinity increases, the holding capacity of water for oxygen decreases. For example, at 200C and 0�/oo salinity*, water can hold 6.4 ml/1 of oxygen, but at the same temperature and 300/00 (seawater), only 5.4 ml of oxygen can be held in one liter of water. A high amount of detritus (organic material) from the marsh can decrease dissolved oxygen just as sewage does. In this case, a spring tide may flush large quantities of dead cordgrass (S. alterniflora) out of the marsh. The microbes attack the detrital material and as they break the material down, oxygen is consumed. *The symbol o/oo means parts per thousand and is a standard measure for the concentration of salt in the water. 244 The great volume of plankton (both zooplankton and phytoplankton) in an estuary consume large quantities of oxygen as they continuously respire. Phytoplankton produce more than enough oxygen during the day, but at night no oxygen is produced. Consequently, during the night, oxygen is lost from the water column as billions of these tiny organisms respire. Finally, it must be remembered that the more obvious organisms, the fish and the benthic organisms--crabs, shrimp, clams and other invertebrates--are all respiring and consuming oxygen. Thus, when all the factors--temperature, salinity, detritus, plankton and animals--are considered as oxygen consumers, one can see how the dissolved oxygen can naturally become depleted. The most vulnerable time for estuarine waters for catastrophic events to occur due to oxvqen saeis is in the summer (when the water is warm); in saline areas, early in the morning (after organisms have been respiring all night), and near a large marsh (where there is a high detritus load). For many years, marine biologists have witnessed catastrophic oxygen sacis resulting in fish kills and the denuding of oxygen-consuming organisms from certain estuarine areas. The questions to which some biologists have addressed themselves include how much oxygen do individuals of differing species Consume and what is the lowest level of dissolved oxygen that can be tolerated by organisms such that a healthy estuarine community is maintained? Since fish consume relatively more oxygen because of their large size and high levels of activity compared to other types of estuarine life, scientists have used fish to determine water quality standards in terms of dissolved oxygen. Gray (1954) in analyzing experiments concerned with the oxygen requirements of estuarine and oceanic species found fishes fall into three categories which 245 relate the oxygen requirements of fishes to their environment and habits; Group I: The active~migrating, streamline fishes of high oxygen consumption. Group IT: The fishes of moderate activity, limited in daily travels and moderate consumers of oxygen. Group III: The sluggish species, more or less adapted for benthic existence and low consumers of oxygen. When studying the results of various experiments concerned with the oxygen demand, consumption and resistance to low oxygen levels of estuarine and marine fishes, the hypothesis of Gray (1954) takes on an added dimension (see Table 3). Although it has been determined that Group I fishes require higher dissolved oxygen concentrations than say Group 1I and Group III fishes, it still must be determined what are the absolute levels of dissolved oxygen these fishes require in the field. Since it is impossible to test every fish in nature, biologists extrapolate information they take from several species and then apply this knowledge to the whole. Every species of fish possesses an inherent rate of oxygen uptake (metabolism) below which it cannot survive. In most cases, the concentration of dissolved oxygen (DO) in the water column is high enough such that a fish is capable of maintaining a rate of oxygen consumption which will permit it to live. Figure illustrates this concept. Line F represents the oxygen uptake of a particular fish as a function of the dissolved oxygen concentration in the environment. For every fish, there exists an environmental oxygen concentration (3 ml/1 in this example) below which it cannot extract enough oxygen from the water to maintain metabolic needs. This environmental DO level and oxygen uptake rate is denoted by point S on line F. Any point on line F to the left of point S indicates a DO concentration and oxygen untake rate which will prove lethal to the fish (in this case, any DO concentration below 3 ml/1). 246 TABLE 8 co Grouping From the Literature of Selected c CM. Estuarine and Marine (U Fishes According to u 4-3 K Physiological Studies and Studies on Their - 0 -4 Resistance, Tolerance c' - - E P ~~~~011 Cn CO and Oxygen Consumption - L- L3 $~~~~~~~~~~~~~- 0 0 ~0 .0 -- CD G - .- - 4- 5- t~~~ S.- _ _ - -%- Species C , - Blueback I I AR-osa aen~tivat~i6 Alewife I I Aeocz pseudohah.ernguz Menhaden I I II I I Iala I Bhevoohtia ty,%annua Silverside I I-TI I Menidiac mentidia Bluefish I II l a la I Pomatomws6 saetathix Mackerel I I I I ScombeAr scombt'w6 Anchovy II II Anclhoa mitckih}i Eel I III II AnguiL&z &ostoAataz Sand perch II II Bai'dieZ&'. ch'tysuwa Blue runner II II Caaznx cAysos Weakfish III II I II II Cynozcion sp. Pinfish II II Lagodon thomboidez a Spot II II II Leiostoamus xanthu.4io Croaker II II MicAopogon unducetuw6 Mullet I II l 1a 11 Mugit cephaia6 Northern searobin II II II I I III II P'io no~tw5 caiwoCiLnu6 Striped bass or perch II II II Motonee 6p. Puffer II III II II II Speroideu macu-atus Scup II II II III I II II II Stenotomuz c'LyopA Sheepshead minnow II III III CYp'&iodon vaiteg~atuz Mummichog or killifish II III III III III Fundutu, . p. Toadfish III III III III III III III III III III Opanws tau Summer flounder III III III Poaaaichthys dentatu- Tongue fish III III Symphwuwu pPagiusa Pipefish III III Syngnathuw uLz6cu,6 Lizardfish III III Synodu6 6oetevn Hogchoker III III TDineeteA macutatus (Adapted from Thornton, 1975) aJuvenile. 247 There also exists DO concentrations in which the fish can live but its level of activity is curtailed. Although the fish can extract enough oxygen from the environment to live, it does not have enough to do a lot of work (swimming); hence, it may become sluggish and consequently more apt to be preyed upon. At this level, the rate of oxygen uptake is dependent on the DO concentration in the environment. This condition exists between 3 ml/1 and 6 ml/l or point S and point L on line F on Figure 77. Above point L (the limiting level) the fish has enough environmental oxygen to do whatever it needs, there is no restriction on its activity or consumption of oxygen. The fish's oxygen uptake is independent of the environmental dissolved oxygen level. Below point L the rate of oxygen uptake for the fish is adequate but limiting. Below point S, the oxygen uptake is not adequate to maintain the life of the fish and consequently, it will eventually die. From an ecological point of view, determining the environmental dissolved oxygen concentrations approximating the limiting level (point L) for species that are highly susceptible to declining or low dissolved oxygen concentrations (Groun I fishes) sets a standard for allowable decreases in dissolved oxygen which presumably permits all estuarine organisms enough oxygen to fulfill their function in the estuary. Limiting levels, however, are difficult to determine experimentally and there are many factors such as nutritional state, age of the fish, activity state, temperature, etc., which affect limiting levels. It is a well known fact that most fish larvae are far more susceptible to low dissolved oxygen concentrations than are adults of the same species. With this in mind, experimenters through the years have made recommendations based on their experiments that have attempted to define and calculate lethal and limiting levels. Ellis (1957) in his work with freshwater fishes determined 248 a standard of not less than 5.0 ppm (3.5 ml/1) should be accepted as a minimum limit of dissolved oxygen. Thornton (1975) in his study of eight species of estuarine fishes in Delaware, concluded that estuarine waters with dissolved oxygen concentrations below 3 ml/1 (5.2 ppm) tend to exclude Group I fishes (See Table 8 ). As discussed earlier, even under natural conditions, dissolved oxygen concentrations can fall below 3 ml/1 in the estuarine environment. This is why it is extremely important to guard against large artificially induced loads (as sewage) in the estuary, since these areas are prone to naturally occurring low dissolved oxygen levels. In Delaware, the State criteria for dissolved oxygen for all tidal portions of stream basins, not including the Delaware River proper, are "daily average concentrations...not...less than 6.0 ppm (4.9 ml/1) nor less than 5.0 ppm (3.6 ml/i) at any time except when natural phenomena causes this value to be depressed". Although almost all forms of estuarine life are capable of living within the minimum dissolved oxygen concentration provided by the State's legal definition--3.6 ml/1--the law also provides that any dissolved oxygen concentration below 3.6 ml/1 is acceptable provided it is induced by "natural phenomena". Unfortunately, in the estuarine realm, it is difficult to distinguish between natural and unnatural causative factors when assessing areas of low dissolved oxygen. Instead of using a fixed value as 3.6 ml/1 for all areas for all seasons, biologists now recommend that a choice of values be offered that gives differing levels of protection based on season, location and degree of protection desired. The criteria are presented in Figure 78 (from Doudoroff and Shumway, 1970). Each curve in Figure 78 represents a relationship between the estimated natural minimal 02 concentration (horizontal scale) for a given area and season, and 249 FIGURE 77 ENVIRONMENTAL DISSOLVED OXYGEN CONCENTRATION ' hi - z * 0 'Gm z -" , . -. . . . . . .// V 6 D. . . /. 0.0 mllI 3 mli l 6 Wil 10 mil/l Shown is the relationship between the rate of oxygen uptake (metabolism) of a species X in respect to the environmental dissolved oxygen concentration. Point 5is the lethal level; point L, the limiting level. I1:W- 0 1 F'IGURE 78 RELATIONSHIP BETWEEN ESTIMATED NATURAL AND ACCEPTABLE SEASONAL MINIMAL OXYGEN. CONCENTRATIONS 7 6 g 5 o 4 . o ;E 3 t-0 in2 0.0 m2/l 3 m4/I 6 nl/i 10 9l/I Shown is the relationship between the rate of oxygen uptake (metabolism) of a species X in respect to the environmental dissolved oxygen concentration. Point S is the lethal level; point Lo the limiting level. FIGURE 78 RELATIONSHIP BETWEEN ESTIMATED NATURAL AND ACCEPTABLE SEASONAL MINIMAL OXYGEN CONCENTRATIONS E .o// 20 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I- u E ~ ~ 1 4 5 / C.) C~~ Estimated Natural Seasonal Minimum Oxygen Concentration (ml/1) (From Doudoroff, P. and D. L. Shumway, 1970) 25O a seasonal minimal that has been judged compatable (vertical scale) with the level of protection specified. Thus, for each estimated natural seasonal minimum oxygen concentration, there is shown a dissolved oxygen level on the vertical scale to which the dissolved oxygen concentration can be artificially depressed below the estimated natural minimum for a given season, while providing some level of fishery protection (determined by lines A-D). As stated, the lines A through D provide different levels of protection for fisheries. The oblique line A offers optimal protection for fisheries because no depression of the oxygen concentration below the estimated natural seasonal minimum level is permitted. This level offers the highest protection and is appropriate for spawning areas. Curve B also offers a high level of protection. For each estimated natural seasonal minimum concentration, only a slight nonnatural or man-induced decrease in dissolved oxygen is deemed acceptable. This level of protection is good for all but the most sensitive species of fishes. Curve C offers only moderate protection for fisheries as it allows even more of an acceptable decrease for each natural minimum oxygen concentration. Finally, Curve D represents a low level of protection because it permits large decreases in dissolved oxygen concentrations below the estimated natural minimum. Different levels of protection then can be applied to different areas during different seasons. Spawning areas should have a high level of protection, denoted by line A or B. Waters which are not used as spawning or nursery areas could provide lower protection perhaps, as shown by line C. Finally, in an area which is not deemed as high priority in terms of fishery protection, Curve D could be applied. All sensitive fish would probably be excluded from areas in 251 which the oxygen situations described by Curve D are in existence, although these fish might have to pass through such areas during their migrations. If this is the case, practices should be initiated during migration periods which would permit the proper oxygen conditions to develop. The application of the system necessitates that the natural seasonal minimums can be determined which, in populated, polluted areas, of course, is impossible. In those cases, reliable estimates by experts will have to suffice. In all other cases, however, past data or new sampling programs could be initiated to determine natural minimums. There is also the possibility that the levels of protection can be adjusted to the season. Since summer is a critical period in the lives of fishes, and also a time when dissolved oxygen concentrations are at their lowest, higher levels of protection should be offered in summer spawning areas. The system, as described here, is meant to be flexible. Finally, it can be seen that all the curves merge approximately at 2 ml/1 on both axes. This means that no depression of the natural dissolved oxygen is acceptable at this level under any circumstances, as few species of fish are compatable with dissolved oxygen concentrations below this level. In conclusion, all animals and plants, with few exceptions, require oxyglen. In the hydrosphere, oxygen is relatively less abundant than in the atmosphere. Although there are many diverse oxygen consuming organisms in the estuary, not all require the same amount of oxygen. Generally, the larger, more active species of animals, such as fish and some large invertebrates require relatively high concentrations of dissolved oxygen. tOan has the canacity to alter dissolved oxygien concentrations by virtue of his various activities. Reduced dissolved oxygen concentrations are 252 associated with heated effluents, sewage discharge, other organic wastes, some industrial discharges, dredging, spoil deposition and others. Nature can also act to reduce dissolved oxygen concentrations through increased salinity and temperature, excess organics (primarily plant detritus) and respiration of animals. Acceptable standards for dissolved oxygen concentrations in estuaries have historically been determined by testing fishes which are susceptable to low dissolved oxygen concentrations. In general, marine bioloqists have deemed values below 3.0 ml/1 not satisfactory for a healthy estuarine ecosystem. States have not incorporated these recommendations into their deemed codes. In Delaware the dissolved oxygen concentration must exceed 3.6 ml/1 except when natural phenomena cause it to be depressed further. A more flexible criteria for setting lower limits for dissolved oxygen is recommended. It is felt that both socio-economic and biological consider- ations can be represented more fairly by this scheme since different levels of protection can be applied to different areas for different seasons. References Brown, C. L. and R. Clarke. 1968. Observations on dredging and dissolved oxygen in a tidal waterway. Water Resources, 4: 1381-1384. Doudoroff, P. and D. L. Shumway. 1970. Dissolved oxygen requirements of freshwater fishes. FAO Fisheries Technical Paper Number 86. Rome, Italy. Ellis, H. M. 1957. Detection and measurement of stream pollution. In: H. E. Brown, ed. The Physiology of Fishes. Volume 1: MetabolisC. Academic Press, Inc., N. Y. pp. 1-53. Sherk, J. A., J. M. O'Conner and P. A. Neumann. 1972. Effects of suspended and deposited sediments on estuarine organisms. Phase II. Report to Environ. Research, C. B. L., Prince Frederick, Maryland. Reference Number 72, 9E. Thornton, L. L. 1975. Laboratory experiments on the oxygen consumption and resistance to low oxygen levels of certain estuarine fishes. Master's thesis. University of Delaware. 253 TEMPERATURE AND ESTUARINE ORGANISMS Temperature affects all living organisms. Most importantly, temperature levels and/or changes in temperature trigger programmed behavioral responses in animals that are specific for each species. Migrations, changes in growth rate, gonad development, spawning periods, and a host of other functions are principally induced by changes in temperature. Every aquatic system progresses through a natural cycle of changing temperature as the seasons change. In the past, little that man did affected the temperature regimes of lakes, rivers and estuaries. Consequently, changes in the natural population and distribution of organisms due to unnatural temperature perturbations were not common, and there was little need to consider the details of the temperature dependencies of plants and animals. Today, however, this is no longer the case. The increased incidences of environmental temperature alterations and the effects on the biotic communities have forced scientists to critically examine temperature - organism relation- ships. The amount of concern now centered on this subject has risen drastically in recent years, and rightly so, for all predictions conclude that the incidences of man-induced temperature alterations will increase in the future. It is no longer a question of whether or not temperature alterations will occur, but how great and frequent these alterations will be. Increases in the incidence of man-induced temperature alterations (thermal pollution) are directly linked to our rapidly expanding society. The qrowth that the United States has realized has come about only through the production of great amounts of energy. Basically, this has meant converting the energy stored in fossil fuels and radioactive materials into electricity. Because of dependency on electrical energy, the generating plants which produce the 254 electricity used have become essential components of contemporary society. Environmental temperature alterations result because of the inefficiencies with which generating plants convert coal and/or radioactive substances into electricity. About 60 per cent of the possible electrical energy content of coal and 70 per cent of that of radioactive materials are converted not into electricity but into heat (Black, 1969; Sorge, 1969). At the present time at least, the heat nroduced is an unwanted by-product of energy conversion processes. Heat represents nossible electricity loss, and it must somehow be channeled away from the power generating stations. The typical means of removing the waste heat is by using lakes, rivers and estuaries as heat receptacles. Water has a high heat capacity, i.e., it requires a large input of heat to raise the temperature and has therefore been used as the substance to cool down the generators and remove the excess heat they create. Most power generating stations are, in fact, located near large bodies of water because cooling water is a prime component of any present-day electrical power generating operation. Water is diverted from its natural course into the generating station, used to cool the generators, and then returned at a higher temperature to the river or estuary from which it was diverted. Small temperature changes on the order of only I or 20C or the use of small amounts of water in such cooling operations are not of great concern. Rises in temperature are commonly on the order of 10 - 200C and may be as high as 300C (Clarke, 1974). Eighty-six fossil fuel plants are discharging thermal wastes into the East coast area in the late 1960's (Sorge, 1969). A typical plant such as the one located in the Indian River area, uses as much as 250,000 gallons of water every minute to cool its generators (Logan and Maurer, 1975). Nationwide, 255 it is estimated that by the 1980's, 1/4 - 1/3 of all the surface water of the United States will be used in power plant cooling operations (Cairns, 1968). That amounts to 300-500 billion gallons of water a day. In essence, these figures suggest that many natural water systems and their biotic commiunities will be experiencing drastic temperature alterations in the very near future, if they have not already been so affected. It is in this climate that more and more emphasis is being placed on studying the relationships existing between the life cycles of organism and the temperature cycles of their environments. If organisms were not seriously dependent on the existence of particular temperature conditions for their survival, alterations to environmental temperatures would not be so critical, but all processes associated with living organisms are affected by temperature. This is so because the basic chemical reactions necessary for the existence of life are themselves affected by temperature levels and by rates of temperature change. Metabolic activity, enzymatic activity, hormonal production, molecular structure, ion activity and gas diffusion are some of the critical temperature dependent, life-sustaining el ements. The reactions that organisms display under particular temperature regimes, notably the development of distinct reproductive, migratory, feeding and growth habits, are biological and behavioral expressions of the temperature dependencies of these basic chemical reactions. Because every type of organism is slightly different from all others, the exact reaction each has to a particular temperature situation will vary from species to species. But since all life is dependent on essentially the same chemical processes, no organisms exist for which environ- mental temperature regimes are not critical to their survival. 256 The thermal pollution problem is especially important to aquatic and marine forms, for these organisms are generally poikilotherm - a technical term meaning cold-blooded. Polkilotherms possess few, if any, internal mechanisms by which they can control their body temperatures, and they therefore assume the temperature of their environment. Most fish, for instance, are known to have body temperatures that usually differ by only .50 - 1.00C from the ambient temperature although some very active swimmers (such as tuna) have temperatures that are as much as 80C above ambient (Sylvester, 1969). Except for the general nature of the life cycle of poikilotherms which is patterned to the temperature cycle of a particular area, these organisms have few means to modify the effects of environmental temperatures. Their survival depends on their abilities to remain in areas where the temperatures allow them to function properly. When environmental temperatures are examined, one facet is particularly striking and of extreme importance as far as the possibility of man-induced modifications is concerned. Temperature is a cyclic phenomenon; there are well established daily and seasonal temperature cycles to which all organisms have become adapted. It is the subtleties of the cycle which man affects more than the absolute temperature levels characteristic of a system. The tempera- ture cycles common in each geographic or climatic region have been developed over many thousands of years. It has taken almost as long for organisms to adapt to these cycles as it has for the cycles themselves to develop. Man is capable of making very rapid and large-scale changes in the environ- ment which seem essential and desirable for man's existence. In the larger natural world, however, it is the slowness of changes and the continual repe- tition of the same kinds of events that are important for the survival of most species. A particular organism may experience a 30 - 400C change in temperature 257 over the course of a year, but the great change in temperature levels is not detrimental to the organism because of the gradual speed with which the change is accomplished. Many organisms, however, would experience extreme stress that could result in their death if taken from a 300C environment and immediately placed in a 00C environment. Few organisms have developed physiological mechanisms or behavioral responses that enable them to survive such a drastic temperature alteration. To a degree, the absolute temperature levels themselves are important, since there are temperatures above and below which each species cannot survive, no matter what the speed of the temperature change. At very high and very low temperatures, basic molecular activity ceases to occur for a variety of reasons. Since organisms are not found in environments where extreme temperatures are common, it is the degree of temperature fluctuations experienced, the patterns of the fluctuation, and the rate at which the fluctuations occur which become the important elements to consider. These are the parameters by which important biological events are timed and the parameters which man can most easily affect (Cairns, 1968). Because of the different properties of air, water, and soil, these materials become variously heated with any particular amount of solar energy. Air is the least dense of the three components and is the quickest to respond to the amount of solar radiation present. Therefore, air heats up faster during the day and cools down faster at night than do either the soil or water. Thus daily and seasonal changes in air temperatures are usually greater than are the daily and seasonal temperatures changes of soils and water. Since the environment of soil and water organisms does not fluctuate as much as does that of terrestrial organisms, there has been little need for them to develop the adaptations needed 258 for survival in as widely fluctuating environments. Accordingly, organisms living in soils and waters can usually only tolerate much smaller deviations from normal temperature cycles than can terrestrial organisms. Most of the temperature dependencies of organisms have been examined in fishes, for fish are often the easiest organisms with which to work and one of the most obvious components of the biotic community. Fish are mobile animals and so are rarely killed directly through exposure to lethal temperatures but are more commonly killed from complications arising when they are exposed to sublethal but stressful temperature situations. Activity and metabolic rates of fish are temperature-dependent although the details of the dependencies are different for each species partially due to body size and innate physiological differences (Brett, 1965; Sylvester, 1969). Rises in temperature usually cause activity levels in fish to increase. To a point, this is not harmful. However, there is a certain activity level which becomes detrimental to the fish. Its body systems begin to work at maximum capacities and the fish dies because it cannot procure enough food or oxygen to sustain the high activity level. Food consumption increases with increasing activity and temperature, but the efficiency of converting food to energy often declines. The higher temperatures responsible for the increased activity also lead to reductions in the oxygen levels of water for warm water has a lower oxygen holding capacity than does cool water. Therefore, while a fish might be able to capture enough food to sustain the higher activity level, the lack of oxygen might lead to asphixiation and prevent the conversion of this food into energy. As the temperature stress becomes more acute, other examples of its effect begin to appear. While the swimming rate might increase, fish often lose control 259 over their swimming ability and begin to move erratically (Jones, 1964; Baldwin 1957). This affects not only their ability to capture prey, but also their ability to avoid being captured by their own predators. This is one of the complications leading to mortalities of fish at subletal temperature levels. There are also indications that some fish become more aggressive toward members of their own species at high temperatures, which may lead to serious dis- ruptions in the social structure of the species (McLarney et. al., 1974). Such a reaction could be especially important to schooling fish, whose sur- vival depends on the close ties existing between individuals of the species and the structure and organization of the school. Activity level and behavioral changes are reflections of the effects of temperature on the enzyme and nervous systems of the fish. Internal activity is directed by the nervous and enzyme systems, so disruptions to these are critical. At certain high temperatures enzymes begin to breakdown and cease to function properly in the chemical reactions in which they are involved. Likewise, the physical structure of the nerves and the chemicals involved in passing messages from one part of the body to another start to change, and directions sent out from the fish's brain are not sent to the right muscles or translated in the proper manner. Another extremely important physiological function which is temperature- dependent is the process of osmoregulation (the ability of the fish to adapt to fluctuating salt environments, a critical ability for all estuarine organisms (Kinne, 1963)). It becomes difficult for fish to maintain the proper ionic balances between its own blood and the water at very high temperatures. Fish can then die from dehydration or high internal salt levels at excessively high temperatures. 260 Because the functioning of these basic physiological processes are directly related to temperature, important phases in the life of fish such as reproduction, growth, and migration are also directly related to temperature cycles. Migra- tions of the bluefish and weakfish, for example, are tied to the changing water temperatures as are their spawning patterns. Like the adults, eggs and larvae have particular temperature ranges outside of which they will not survive and develop properly, and spawning is timed to occur when temperature conditions in the spawning area are at the levels needed for proper egg and larval development (see Environmental Requirement Tables). Power plants, through their constant heating of water, tend to upset these cyclic movement of organisms. Fish normally found in summer in a particular area are forced out of the area in the warmer seasons because the additional heat from thermal wastes causes water temperatures to rise above tolerable limits. Yet, in winter these same fish are often drawn to the area of the thermal addition, for the normally too cold winter waters are now warm enough for them to exist in. The picture becomes even more complex, for while some species disappear, some eventually become adapted to the new situations and seem to do well in them. Should the power plant decrease or increase its flow, change the discharge temperature levels and discharge areas, or shutdown for repairs, these changes would be reflected in changes in the water temperature with subsequent possible catastrophic results to the biotic community. Temperature affects the same physiological processes in eggs and larvae as it does in adults except that the abilities of the young to adapt to new conditions are generally not as great. Further, eggs and larvae have limited powers of movement so they cannot easily move from areas of adverse temperature conditions to more suitable ones. While the eggs and larvae might not die under 261 improper temperature conditions, their development might be so affected that they cannot perform properly during other stages in their lives. Such long term changes in the health of the fish can be just as detrimental to the populations as can immediate mortalities occurring at the egg and larval states. Migration and spawning patterns have developed so that all these temperature- related problems are overcome to some degree under natural situations. Temperature affects all other estuarine organisms in similar ways. Metabolic rates, reproduction activity, growth rates, community structures and species successions of zooplankton are known to be temperature dependent (Heinle, 1969), as are those of many benthic organisms and communities (Pearce, 1969; Logan and Maurer, 1975; Tinsman, 1973; Nauman and Cory, 1969). The oyster community in the Indian River area has been studied in light of effects of thermal discharges originating from the Delmarva Power and Light plant at Millsboro (Tinsman, 1973; Tinsman and Maurer, 1974). It was found that the effluent moderated the effects of the winter season but intensified the effects of the summer season. Oysters placed in the effluent grew better in the winter than oysters outside the effluent zone. In the summer their growth was reduced,compared to that of oysters outside of the effluent,because of the extreme conditions caused by the high water temperatures in the dis- charge area. There are indications that some premature spawning occurred in oysters placed in the thermal effluent, which is an indication that the unnatural temperature situation might affect the basic life cycle of these organisms. Aquatic and estuarine plants are also known to be dependent on particular temperature regimes for their existence (Wood and Zieman, 1969). The dis- appearance of widgeon grass (Ruppia maritima), for example, and its replace- ment by other species in some areas of the Patuxent River in Maryland has 262 been traced to the change in temperature conditions brought about by thermal additions from a power plant (Anderson, 1969). Photosynthetic rates, oxygen and GO2, exchange, and reproduction seem to be the most temperature-dependent parameters i nvol ved. Even the simplest of estuarine organisms, the phytoplankton, are known to be temperature-dependent (Coutant, 1971; Patrick, 1969; Morgan and Stross, 1969; Warinner and Brehmer, 1966). Again photosynthetic rates, oxygen production, cell division and reproduction, and species succession can all be correlated to temperature levels. For instance, diatoms, a most important group of phytoplankters, usually disappear in waters above 300C, and are replaced first by green algae and then by blue green algae at progressively higher temperatures. Such successional chains occur in response to natural cyclic temperature changes but can also be induced by alterations in these cycles through additions of thermal wastes. As with other cyclic alterations, there is unfortunately very little data which allow researchers to evaluate the importance of such changes. It has been pointed out that "the entire controversy surrounding thermal discharges has become one of affiliative semantics. The conservationist refers to it as thermal pollution, the utility company as thermal enrichment and the objective biologist as thermal addition", (Sorge, 1969). This statement effectively points out the dilemmna planners often find themselves in when considering the thermal waste question. In many instances, it is hard to pre- dict what the effects of temperature manipulations will be. Even though complete knowledge of the effects is not available, most researchers feel that some standards should be set to control the additions of thermal wastes. Delaware has moved in that direction by including in its 263 Water Quality Standards some regulations concerning temperature additions. Certain areas in each stream or bay have been designated as mixing zones and these will receive a large part of the waste heat load. The only criteria for temperature additions in the mixing zone is that they should not be so great as to cause death of fish and shellfish in these areas. Outside the mixing zone, which is different for every creek, river and bay because the size of the zone depends on the physical character of each system, temperature changes cannot cause water to exceed 85OF or raise temperature by more than 4OF from September through May, or by more than 1.50F from June through August. There are some concerns about these regulations, but they are at least initial steps in controlling thermal waste additions and indicate that some attention is being given to the problem. There are enough examples to indicate that many of the effects of temper- ature manipulation are harmful to some groups of organisms. Migration, reproduction and growth patterns of fish and other animals are upset when temperature cycles are modified as are photosynthetic, gas exchange, repro- ductive and successional patterns of phytoplankton and other marine plants. There is evidence also that the effects of temperature manipulations must not be looked at alone, for disruptions to other parts of the habitat will have effects on the responses of organisms to temperature changes. Some substances are known to be more toxic to fish at higher temperatures because the capabili- ties of fish to combat the effects of toxic materials and even some natural diseases are reduced (Jones, 1964). Likewise, substances such as the pesticide, dieldrin, are known to hinder the responses of fish to changing temperature (Silbergeld, 1973). In situations where thermal pollutants and chemical pollutants occur together, the harmful effects of each are reinforced by the 264 presence of the other producing critical situations for many organisms which researchers may not even have considered. There are some apparently beneficial effects of temperature modifications. Slight temperature increases do lead to productivity increases at most ecosystem levels. But there are many facets to these increases about which researchers have very little data. In such instances, most of the concern centers around the long-range effects that might appear several years after the sublethal temperature modifications occur. These concerns, the incidences of deleterious man-induced temperature alterations and the known dependency of all organisms on natural temperature cycles, suggest extreme care when planning activities that might in some way alter the temperature cycles to which organisms are so closely adapted. References Anderson, R. R. 1969. Temperature and rooted aquatic plants. Ches. Sci. 10: 157-164. Baldwin, N. S. 1957. Food consumption and growth of brook trout at different temperatures. Trans. Am. Fish. Soc. 86: 323-328. Black, D. S. 1969. Keynote address. In: Biological aspects of thermal pollution, proceedings of the natinal symposium on thermal pollution. Krenkel, P. A. and F. L. Parker, ed. Vanderbuilt Univ. Press. pp. 3-9. Brett, J. B. 1965. Swimming energetics of salmon. Scientific Am. 213: 80-85. Cairns, J., Jr. 1968. We're in hot water. Scientist and Citizen 10: 187-198. Clark, J. 1974. Coastal ecosystems. The Conservation Foundation, Washington, D. C. Coutant, C. C. 1971. Thermal pollution -- biological effects. A review of the literature of 1970. Water Pollut. Contr. Fed. 43(6): 1292-1334. Davis. H. S. 1967. Culture and diseases of game fishes. Berkeley, Univ. Cal. Press. 332 pp. Heinle, D. R. 1969. Temperature and zooplankton. Ches. Sci. 10: 186-209. 265 Jones, J. R. E. 1964. Fish and river pollution. Butterworths, London. Kinne, O. 1963. The effects of temperature and salinity on marine and brackish water animals. 1. Temperature. Ocean Mar. Biol. Ann. Rev. 1: 301-340. Logan, D. and D. Maurer. 1975. Diversity of marine invertebrates in a thermal effluent. J. Water Poll. Contr. Fed. 47: 515-522. McLarney, W. 0., D. G. Engstrom and J. H. Todd. 1974. Effects of increasing temperature on social behavior in groups of yellow bullheads (Ictalurus natalin). Envir. Poll. 7: 111-119. Morgan, R. P. and R. G. Stross. 1969. Destruction of phytoplankton in the cooling water supply of a stream electric station. Ches. Sci. 10: 165-171. Nauman, J. W. and R. L. Cory. 1969. Thermal additions and epifaunal organisms at Chaulk Point, Maryland. Ches. Sci. 10: 218-226. Patrick, R. 1969. Some effects of temperature on freshwater algae. In: Biological aspects of thermal pollution. Kaenkel, P. A. and F. L. Parker, ed. Vanderbuilt Univ. Press. pp. 161-185. Pearce, J. B. 1969. Thermal addition and the benthos, Cape Cod Canal. Ches. Sci. 10: 227-233. Silbergeld, E. K. 1973. Dieldrin. Effects of chronic sublethal exposure on adaptation to thermal stress in freshwater fish. Envir. Sci. and Tech. 7: 846-849. Sorge, E. V. 1969. The status of thermal discharges east of the Mississippi River. Ches. Sci. 10: 131-138. State of Delaware, Department of Natural Resources and Environmental Control. 1974. Amendments to Water Quality Stand for Streams. Adopted May 15, 1974, Effective May 15, 1974. Sylvester, J. R. 1972. Possible effects of thermal effluents on fish: a review. Envir. Pollut. 3: 205-215. Tinsman, J. C. 1974. The effects of thermal effluent on the American oyster, Crassostrea virginica Gmelin, in Indian River Bay, Delaware. Master's thesis. University of Delaware. 126 pp. Tinsman, J. and D. Maurer. 1974. The effects of thermal effluent on the American oyster, Crassostrea virginia Gmelin, in Indian River Bay, Delaware. Del. Sea Grant Publ. #DEL-SG-17-74. 115 pp. Warinner, J. E. and M. L. Brehmer. 1966. The effects of thermal effluents on marine organisms. Inter. J. of Air and Water Poll. 10: 277-289. Wood, E. J. F. and J. C. Zieman. 1969. The effects of temperature on estuarine plant communities. Ches. Sci. 10: 172-1976. 266 TURBIDITY The source of suspended sediments, the general levels of suspended sediments in the Delaware estuary, and the tolerance limits of many organisms have been discussed in the Agriculture and Spoil Disposal sections on Wetlands Destruction, and in the listing of Environmental Parameters. Little additional data for the tidal streams and estuaries can be added here. Principally suspended sediment affects estuarine organisms in these ways: 1. Suspended sediments increase the oxygen demand in the water column due to increased microbial action (consequently community respiration) on detrital particles. This causes dissolved oxygen to decrease, imposing potential hazards on organisms highly susceptible to oxygen deprivation (see Dissolved Oxygen and its Relationship to Estuarine Organisms). 2. Suspended sediments inhibit transmission of light through the water column, thus decreasing the standing crop of phytoplankton. Phytoplankton helps form the base of the estuarine food web and is a primary producer (see General Principles of Wetlands Ecosystem; Food Web). 3. Suspended sediments can introduce toxic materials to the water column, such as pesticides (chlorinated hydrocarbons), heavy metals and radionuclides. These materials are selectively incorporated into organisms by biological magnification causing lethal and sublethal effects. 4. Suspended sediments clog the gills of fishes, inhibiting carbon dioxide-oxygen exchange and causing asphixiation. 5. Suspended sediments clog the nucous membranes of many suspension and filter feeders by mimicking the size of the host organisms food particles. This causes inefficient feeding, choking, clogging and in many cases, death. 6. Suspended sediments can smother benthic organisms when they settle, physically covering and smothering whole organisms. 267 7. The deposition of suspended sediments can cause shoaling, the intro- duction of new flow patterns and salinity distributions. Shoaling can disrupt navigation. Changing salinities can increase stress on organisms (see Salinity and Estuarine Organisms). References See references in Agriculture and Spoil Disposal discussions under Wetlands Destruction. SALINITY Salinity is defined as the total amount of solid material that is dissolved in a kilogram sample of water. The water of all natural systems contains some dissolved solid substances, because water dissolves these solid materials when it comes in contact with soils and rocks. However, the total amount of dissolved salts, as the dissolved mineral substances are called, can vary greatly. Fresh- water contains small, almost undetectable amounts of salts; ocean water, on the other hand, contains relatively large quantities of salts -- usually 35-35 grams in every kilogram of water. In the very specialized system of "brine pools", the dissolved salt content of the water can often be well over 100 grams per kilogram of water. Estuaries are typically characterized by salinities that range between 10 and 29 grams of dissolved salt per kilogram (10-290foo). Almost all of the natural elements known to man can be found dissolved in the waters of the sea. Onlyv a few of the earth elements, however, can be found in any appreciable amounts in seawater. Chlorine accounts for 55 per cent of the total amount of dissolved salts, sodium 30.6 per cent, sulphur 7.7 per cent and magnesium 3.7 per cent. The rest of the one hundred or so elements together account for only 3 Per cent of the total amount of the dissolved salts 268 found in the Atlantic ocean off the cost of Delaware as well as all other oceans. Most people are aware that plants and animals tend to be associated with environments of particular salinities. Summer flounder are not caught in freshwater lakes, nor are rainbow trout caught in the ocean. Similarly, most of the plants found in backyards are not the same ones found growing in the salt marshes or along the dunes of the beaches. It appears that every organisms can survive only where the salinity conditions of its environment fall within particular limits. To understand why this is so, it is necessary to discuss some of the properties of organisms and some of the properties of their environments in terms of their chemistry. All organisms are basically the same in that they are composed largely of chemical solutions. Cellular cytoplasm, the blood of animals, and the vascular fluids of plants, for example, are all solutions of water and various amounts of dissolved salts, sugars, minerals, proteins and gases. Molecules of water account for 65 to 90 per cent of the material of the cells of every plant and animal. The other substances are present in much smaller and more variable amounts. While the exact chemical nature of the internal fluids of every orqanisms is slinhtlv different from those of all other organisms, the importance of the fluids to the survival of each organism is the same. The composition of these chemical solutions must be continually maintained within certain limits or the organism will die. The specific reasons why body fluids are so important are very complex and diverse, but it can generally be said that every life sustaining process is basically a series of chemical reactions. The correct substances must be 269 present in the proper amounts in the internal fluids of plants and animals for these processes to be successful. Nervous stimulation in higher animals, for example, is dependent on the changing concentrations of sodium and potassium within and without the nerve cells. Similarly, photosynthesis in plants is dependent on reactions involving the nitrogen and phosphorous molecules that are transported from the soil in which the plant grows to the leaves via the plant's root and conductive systems. When examining the life cycles of organisms, the importance of these chemical processes and solutions must be kept in mind. The movement of fishes in and out of estuarine areas, the consumption of shoots of succulent marsh grasses by meadow mice and muskrats, the folding and unfolding of the leaves of plants, and other common activities of organisms can all be directly related to the processes of maintaining proper internal chemical solutions. Maintenance of internal fluid concentrations involves controlling the movements of the molecules of many substances, including water, both within the organism and between the organism and the environment. Such maintenance is a continual process primarily because the chemical characteristics of the environment are different from those of the internal fluids of most organisms. Some elements must be present inside the organisms at concentrations which far exceed the ambient or external concentrations of similar elements within the environment and vice-versa. Plants and animals, then, must continually collect and concentrate vital elements and eliminate waste or non-essential elements. Considerable energy must be expended by organisms to maintain concentration gradients across membranes because such gradients defy thermodynamic principles 270 that affect the movements of all molecules. Leflt on their own, molecules in a particular system will tend to become randomly distributed throughout the system. For example, if a quantity of salt is dissolved in a tank full of freshwater (Figure 79-A), after a time the salinity of any water sample taken from the tank will have the same concentration of salts as all other samples (Figure 79-B). At the instant the salt is added, salt molecules are concentrated in a small area of the tank (Figure 79-A). This arrangement is not thermody- namically stable; consequently, the salt and water molecules tend to become ,redistributed such that a more stable arrangement exists -- one in which salt and water molecules are equally distributed throughout the tank (Figure 79-B3). How this molecular movement affects organisms can be demonstrated by modifying the tank slightly. If a special porous membrane were to be placed across the middle of the tank (representing the skin of a fish), it would stimulate the internal and external environment of an organism. If salt were to be added to Cell A (Figure 79-C) of the tank, the molecular arrangement of the entire tank would initially be unequal and unstable. Even with the mem- brane in place, the molecules of salt and water would have a tendency to redistribute themselves such that a more stable situation would exist as in Figure 79-B. If the membrane were permeable to water only, the water molecules would in fact move from Cell A to Cell B across the membrane (Figure 79-D). Conversely, if the membrane were permeable to salt molecules, the salt molecules would move from Cell B to Cell A (Figure 79-E). The result in both cases would be that a more equal distribution of salt and water molecules would occur in the tank. Essentially the same processes take place between a living organism and its environment. The skin of a fish, like the partition in the tank, is a 271 FIGURE 79 aISalt .-n //1 / -ie =- - : _ X Sketch A I. *'0 ' *' ]Water Molecules l0 . f.. o �o o__ _ /_ Salt Molecules o _. , 0 ,o _ C, . Sketch B o _ _ _ , , - , O - .---1 "1-- � -r - . . .. .Sketch C O �e o 1 g. go; 1 Cell A f Cell B/ Water Permeable Membrane Permeable Membrane 1 I 1 / ,- __ -- -Sketch D !- 1 *0'. . _ . e c0 ';;0 'do ."' � Cell A Cell B SketchE �o Cell A / Cell B Salt Permeable Membrane 272 porous membrane separating different types of solutions. On one side of this membrane are the internal solutions of the fish and on the other side are the environmental solutions (such as the water of an estuary or the ocean); each solution has a particular concentration of elements. If the concentra- tions of elements in the internal and external solutions are unequal, the unequally distributed molecules will have a tendency to move such that they are more equally dispersed just as the salt and water molecules moved in Figures 79-D and 79-E. There exists a fundamental difference between molecular movement in the tank system and molecular movements in organisms. As mentioned earlier, particular internal concentrations of elements must be maintained by a fish if it is to survive. While the tendency for the molecules is to move randomly across the skin of the fish to reduce the concentration differences, in reality the fish must expend energy to actively concentrate and hold the molecules of some elements and "pump" to the environment molecules of other undesired elements. Since the internal and external solutions associated with the fish are always different, such energy is continually expended by the fish. The process of regulating the flow of molecules back and forth across cellular membranes by an organism is called osmorequlation. The prefix is taken from the word osmosis -- the process by which materials diffuse, or move, back and forth across permeable membranes. The word regulation indicates that energy expenditures are involved in the process. While the osmoregulatory problem is shared by all organisms, the nature of the problem each faces is unique for each organism-habitat pair. Since freshwater contains very small amounts of dissolved salt, most organisms 273 living in freshwater environments possess body fluids that contain more dis- solved substances than do the waters in which they live. If freshwater organisms did not expend energy In osmoregulation, water molecules would have a tendency to move into the cell and molecules of the substances dissolved in the cell would have a tendency to move out. Without regulation, freshwater organisms would gain so much water that their cells would literally burst or lose so much internal salts that the chemical reactions necessary for the survival of the organisms would cease. Conversely, saltwater contains very large amounts of dissolved sub- stances, and organisms living in saltwater environments find themselves in water which is saltier than are their own body fluids. Saltwater organisms, then, continually face loss of water molecules from their cellular solutions and addition of salt molecules to them. Their osmoregulatory energy is expended to collect and hold water molecules and excrete excess salt molecules. If saltwater organisms were not successful at this process, their cells would dehydrate from excessive water loss or accumulate a toxic concentration of salts. Some environments are considerably more difficult for organisms to exist in than are others. Estuarine environments are thought of as the harshest environments in which to exist because organisms are faced with constantly fluctuating salinity conditions. While saltwater organisms exist in environ- ments which are always saltier than are their internal body fluids, and fresh- water organisms live in environments always less salty than are their internal fluids, estuarine organisms exist in environments which alternate between being more and less salty than their body fluids. Consequently, estuarine plants and animals must be able to move water and salt molecules against changing concen- 274 tration gradients depending on the external salinity. Throughout the course of evolution, very few organisms have been able to develop the physiological and behavioral mechanisms which allow them to osmoregulate under the constantly fluctuating estuarine conditions. Organisms distribute themselves throughout environments in which they can successfully osmoregulate, and a very close correlation exists between the distributions of environmental salinities and the distributions of organisms. The zonation of plants in response to the salinity characteristics of different environments has already been discussed (see General Principles of Wetlands Ecosystems) and similar zonations also are exhibited by animals. For example, the clearnose skate and little skate are never found in waters below 20%0 salinity; the white catfish is never found in waters above 14.5%o; the oppossum shrimp is never found in waters below 4-5%o salinity. The patterns are, of course, much more complicated than described here for numerous factors must be taken into account when discussing the salinity-related distributions of any plant or animal. The salinity tolerances of all organisms change with different life cycle stages. Most people are familiar with anadromous fish such as the shad and striped bass which live as adults in saline waters but return to freshwater rivers and streams to spawn. The eggs and larvae of these fish can develop properly only in fresh or slightly brackish waters and the migrations of these fish are behavioral responses to this need. There are also catadromous fish such as the American eel which exhibit just the opposite migratory pattern. Adult eels travel from fresh and brackish water areas to oceanic areas to spawn because the eggs of the eel develop properly only in full-strength sea- water. Even more complicated patterns are exhibited by such species as the 275 WILM ING TON * ~~~~~~~~FIGURE 80 kI ~~.:.t SALINITY DISTRIBUTION OF DELAWARE'S TIDAL WETLANDS LEGEND TYPE OF WVATER/SALINITY (PPT) * ** *. ~~~~~~FRESH WATER/LESS THAN 0.50 * . ~~~~~~~~ ~~BRACKISH WVATER/0.50 TO 17.0 .A'~ BAY WATE R/17.0 TO 29.0 I~~ SEAWVATER/GREATER THAN 29.0 ... ..... GEORGETOWN 276 menhaden; the adults, eggs and fry of which require higher salinities for survival but the larvae develop properly only in water below 6%o* Similarly, salinity distribution patterns have been determined for zooplankton organisms, molluscs, crustaceans, worms, and all other types of animals (see Environmental Requirement Tables). The osmoregulatory mechanisms that organisms have developed are as varied as the organisms themselves. Some, such as the structure and function of the kidneys and gills of fishes -- both of which are involved in osmoregulation -- are physiological mechanisms. Others, such as the migration patterns of fish or the opening and closing of the shells of bivalves, are predominantly behavioral ones. All mechanisms, however, have developed so that organisms can successfully complete the reproduction, gas exchange, pH regulation, food assimilation, and other vital processes in the environments in which the organisms are found. If changing salinity conditions require greater osmoregulatory capabilities than an organism possesses, that organism must move to less stressful areas or it will perish. References Numerous references dealing with this subject are included in those provided under the Environmental Parameters discussion. TIDAL FLUSHING Much interest has been centered in recent years on the problems of understanding and characterizing the flushing patterns of the tidal creeks and estuaries. Flushing time is a measure of the time necessary for a particular mass of water to pass through a creek or estuary or any one section of these 277 systems. Therefore, it is the flushing pattern which partially defines the movement of water through the creeks and estuaries. Flushing patterns also define the movements of any waterborne materials, including nutrients, phytoplankton and zooplankton organisms, eggs and larvae of fish and shellfish, sediments and pollutants. These and many other materials are constantly moving through the tidal creek-estuarine system and being transported from one section to another. The exchange of materials between the creeks and upland areas and the estuarine and oceanic areas is possible only because of the flushing of these systems. Therefore, before these exchanges can be fully understood, the flushing and circulation patterns of the tidal creeks and estuaries must be fully investigated. Such knowledge becomes especially important in light of the many types of pollutants being introduced into our water systems every day. Industries and cities have always developed near water sources because water facilitates the waste disposal problems cities and industries must overcome. With more pollutants constantly being dumped into the tidal creeks and estuaries, it becomes imperative to know where these materials will be carried and how long they might remain in any one section. With this knowledge, planners will be able to envision what the effect of particular pollutant loads will be on the biotic community of any creek or estuary and make intelligent decisions concerning the placement of cities and industries along water systems. The calculation of flushing time depends on the knowledge of the many parameters of each system. Measurements must be made of stream flow, tidal flow, in some cases wind flow, cross sectional area, and the general topography of each stream or bay. Further, such measurements must be made at several points 278 in each system and at several times throughout the year, for flushing times change both temporarily and spatially in each creek and estuary. As creek beds become narrower or wider, as seasonal rainfall increases or decreases, and as tidal periods change from spring to neap tides, the flushing times change, often in very drastic ways. As the flushing times change so do the exchange and transport times of the many waterborne materials that are carried back and forth between the creeks, bays, estuaries and oceans. Unfortunately, the measurements needed to describe the flushing patterns of the water systems in Delaware have been made on only a few'of the streams and bays of the State. The Broadkill River and the Murderkill River have been investigated and accurate estimates of flushing times for these two systems are available. Measurements are being taken continually in Delaware Bay that will be used to predict the fate of pollutants introduced into the bay waters. Outside of these studies, however, flushing data is generally lacking for most of the water systems of the State. While specific data is not available on all systems, it is possible to construct a generalized flushing map of the tidal creeks and small bays of the State. Following the work done on the Broadkill and Murderkill Rivers, each system was divided into three sections. The lowest section includes the mouth of the creek or bay and that is the area under the most direct influence of the tides. The middle section is located farther up the system, and while still influenced by tidal activity, it is not as strongly influenced by the tides. The upper creek area generally begins at the transition zone between fresh and brackish waters, and it is, therefore, not directly influenced by tidal activity. 279 These flushing zones were delineated in the Murderkill and Broadkill Rivers from measurements taken to specifically investigate the flushing characteristics of these two systems. Since such measurements are not generally available for the other creeks and bays, the delineations of the zones in these systems were made through investigations of peripherally collected data that does, however, give some indication of the flushing patterns of the creek. Various amounts of data on salinity, vegetation changes, stream flow,ithe length of the system tidally influenced, and distributions of some organisms are avail- able for all of these systems. While the zones created are founded on the best available information and can give planners some insight into the flushing characteristics of each system, it must be emphasized that the zones created are only rough approximations. More data of a site, knowledge of its specific nature, will have to be gathered to assure that the zones delineated are in fact correct. It is easy to visualize how flushing maps in general would help coastal zone managers plan the site selection of cities and industries. Each zone is characterized by particular flushing times that indicate how long water remains in any particular area. The upper creek zones are characterized by the longest flushing times, the middle zones by moderate flushing times and the lowest zones by the fastest flushing times. Materials introduced into the water systems at these particular sections would then be removed and diluted in various times as a reflection of their characteristic flushing time. Managers, knowing the kinds and amounts of materials a particular industry 280 might be introducing into the water and the flushing characteristics of each particular system, would then be able to decide where an industry could locate and how much material, if any, it should be allowed to dump into a creek or bay. In the Broadkill study, for instance, it is pointed out that the up- stream area has become very degraded because of the discharge of large volumes of pollutants into the system in this relatively slowly flushed section. As the wastes pass through more highly flushed areas, they become more diluted and more quickly removed. The indications are that discharges in the upstream area should be more strictly controlled. The obvious answer to site selection problems may appear to be that all industries should be built in the first or lowest zones. Here, waters and waste materials would be most quickly mixed with water from Delaware Bay and apparently rendered harmless. It must be kept in mind, however, that the highly flushed areas are also populated by many organisms because of the constant supply of nutrient and food materials available there. Such zones are some of the most productive of the wetlands areas simply because of the large amounts of nutrients that are constantly being transported through them. These areas benefit from the organic matter contributed both by upstream areas and by the Delaware Bay and ocean and are, indeed, productivity storehouses. To seriously alter these areas and expose them to the problems of industrial manipulation does not appear to be the best course of action. Knowing this, managers should wisely choose another stream section, moderately flushed and less intensively used by organisms, to receive the waste loads. It must be kept in mind, however, that since the flushing time is longer there, reduced pollutionial inputs will be necessary so that the system does not become overloaded. Further considerations must be given to 281 Figure 81 TIDAL FLUSHING MAP OF DELAWARE N MI14LES5 ZON6 z AeCiw or ZVTCN5iLIC r'ivnc ZONC I![7 APCAS OF ,ODCPATC716- D46 ZOIVCZZZf 4R645 or POOP 77 046 282 possibilities such as restricting inputs only to certain times when flushing is greatest or possibly only to certain systems, and prohibiting pollution introductions into systems already unable to dilute the waste materi~ls they contain. These are the considerations managers must take into account in determining site selection for industries and cities, while using flushing maps such as the one prepared for this report. References Bowden, K. F. 1963. The mixing process in a tidal estuary. Intern. J. Air and Water Pollution 7: 343-356. Bowden, K. F. 1967. Circulation and diffusion. In: G. H. Lauff, ed. Estuaries. Pub. No. 83, AAAS, Washington, D. C. pp. 15-36. deWitt, P. and F. C. Daiber. 1973. The hydrography of the Broadkill River estuary, Delaware. Ches. Sci. 14: 28-40. deWitt, P. and F. C. Daiber. 1974. The hydrography of the Murderkill estuary, Delaware. Ches. Sci. 15: 84-95. Ketchum, B. H. 1950. The exchange of fresh and saltwaters in tidal estuaries. J. Mar. Res. 10: 18-38. TOXIC MATERIALS The effects of various toxic materials on the wetlands and water resources of Delaware are discussed throughout the Atlas. Silt, sewage, heavy metal and oil pollution are discussed in detail in the section entitled, "The Relation- ship Between Wetlands and Estuarine Water Quality". A complete discussion of thermal pollution can be found in "Temperature and its Relationship to Estuarine Organisms". Finally, information on pesticides and their effects on wetlands and water resources has been included under "Agriculture in the Wetland Destruction" essays. This article also contains information on silt. Appro- priate references are located in those sections. 283