value and vulnerability of coastal resources background papers for review and discussion

[From the U.S. Government Printing Office, www.gpo.gov]

PB-247-693

Coastal Zone
information
Center The Value and Vulnerability
Of Coastal Resources
Background Papers
for Review
and Discussion

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V35 N.
1975

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BIBLIOGRAPHIC DATA Report No. 2. 3. Recipient's Accession No.-
SHEET GADNR/OPR - 75/1 1
4. Title and Subtitle 5. Report Date
THE VALUE AND VULNERABILITY OF Prepared May 1975
COASTAL RESOURCES: BACKGROUND PAPERS 6.
FOR REVIEW AND DISCUSSION
7. Author(s) 8. Performing Organization Rept.
Lillian F. Dean, et al. No.
Performing Organization Name and Address 10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Address 13. Type of Report & Period
Covered

14.
15. Supplementary Notes Funded in part by National Oceanic and Atmospheric
Administration for Georgia Coastal Zone Management Program.
16. Abstracts
Identification of the values and vulnerabilities of natural

resources is an important first step in resource planning. Policies

and programs for managing and utilizing resources should be based upon

such information. The purpose of these background papers is to high-

light important characteristics of Georgia's coastal resource features

and systems inc luding resource values and vulnerabilities.

17. Key Words and Document Analysis. 17a. Descriptors

In % @In
INFORMATION CENTER

17b. Identificts/Open-Ended Terms

17c. COSATI Field/Group

18. Availability Statement 19.. Security Class (This 21.'No. of Pages
Report) 332
U4C 1 @AJS81,F (ITED
Release unlimited 20. Security as his 22. Price
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Pepartutient of Yatural Frovurces
270 WASHINGTON ST.. S.W.

ATLANTA, GEORGIA 30334
lot P. Tunmr (404) 656-3500
COMMISSIONER
June 15, 1975

I ampleasedto present to you a series of background
papers on "The Value and Vulnerability of Coastal Resources."
These papers were written by individual scientists and
researchers in the University system of Georgia and in the
Department of Natural Resources, for the Georgia Coastal
Zone Management Program. The purpose of the papers is to
present, in summary form, available information on the
benefits resulting from the natural functioning of
coastal resources, and the susceptibility of these resources
to change. This is important background information that
should be used in developing coastal zone management
policies and programs.

These papers were prepared in draft form in January,
1975, and circulated to interested scientists and researchers
for review and comment. Based on the comments received,
I feel that these papers are very useful statements of the
values and vulnerabilities of coastal resources.

Sincerely,
@
Joe D. Tanner
Co issioner

JDT/ldp
Jo e D
Co is

THE VALUE AND VULNERABILITY OF COASTAL RESOURCE X

BACKGROUND PAPERS FOR REVIEW AND DISCUSSION

Prepared by:

Resource Planning Section
r<N Office of Planning and Research
Georgia Department of Natural Resources
270 Wash-2ngton Street, S.W.
Atlanta, Georgia 30334

May, 1975

Coastal Zone Management Technical Committee:

Brunswick-Glynn County Joint Planning Commission
Board of Regents of the University System
Chatham County-Savannah Metropolitan Planning Commission
Coastal Area Planning and Development Commission
Georgia Departmen-_ of Community Development
Georgia Departmen-_ of Human Resources
Georgia Departmen-: of Natural Resources
Georgia Department of Transportation
Georgia Forestry Commission
Georgia Ports Authority
Georgia Soil and Water Conservation Committee
Office of Planning and Budget (Lead Agency)

Credits:

Special assistance on this report was provided
by the Institute of Natural Resources,
University of Georgia.

This publication was funded in part by N.O.A.A.,
U. S. Department of Commerce, for the Georgia
Coastal Zone Management Program.

CONTENTS

PAGE

CHAPTER 1: A Resource Planning Process for Georgia's Coast ....... 1
Purpose of Background Papers ...................... 1
A Resource Assessment Process for Georgia' s Coast . . 2
Resource Policies and Programs .................... 7

CHAPTER 2: The Value and Vulnerability of Coastal Beaches, Sand
Dunes, and Offshore Sand Bars ......................... 9
Introduction ...................................... 9
Nature of Existing Information ................... 11
The Value of Dunes, Beaches and Offshore Bars ... 12
Critical Features ................................ 24
Sensitivity and Vulnerability .................... 26
A Buffer Zone .................................... 29
Selected Bibliography ............................ 31

CHAPTER 3: Terrestrial Ecology of the Georgia Barrier Islands .... 35
The Island Experience ............ ............... 35
Physical Factors Shaping Coastal Island Ecology..37
Soils ............................................ 54
Nutrient Cycles .................................. 62
Coastal Island Fauna ............................. 67
Aquatic Systems .................................. 72
The Strategy of Survival on Coastal Islands ...... 84
Island Communities ............................... 87
Summary ......................................... 102
Selected Biblicgraphy ........................... 111

CHAPTER 4: The Value and Vulnerability of Fresh Water
Ecosystoms .......................................... 113
Introduction .................................... 113
Direct Values: Stream Channels ................. 115
Direct Values: River Swamps .................... 123
Indirect ValueE ................................. 128
Vulnerabilities ................................. 131
Selected Bibliography ........................... 134

CHAPTER 5: A Summary of Ground Water Conditions - Coastal
Georgia ............................................. 137
Introduction ..................................... 137
Basic Concepts ................................... 138

PAGE

Aquifers in Coastal Georgia ................... 142
Water Use in Coastal Georgia .................. 154
Stress to the Aquifer ......................... 158
Summary ....................................... 166
Selected Bibliography ......................... 168

CHAPTER 6.: An Overview of Coastal Wildlife ................... 171
Introduction ..... ...................... 171
Coastal Habitats and their Animal Dependents..173
The Continenta 1 Shelf ......................... 174
The Beach and Dunes ........................... 175
'The Barrier Islands ............................ 177
The Marsh and Estuary ......................... 178
Rivers and Fresh Water River Swamps .......... 179
The Nature of Existing Information ............ 181

CHAPTER 7: Coastal Georgia's Cultural Resources .............. 183
Coastal Zone Management Act ................... 183
An Arena of History ........................... 184
"The Debatable Land ............................ 186
Conservation of Historic and Archaeological
Sites ......................................... 190
Action at the State and Local Level ........... 193
Selected Bibliography ......................... 199

CHAPTER 8: Soils Information for Coastal Georgia ............. 201
Soil Characteristics and Mapping .............. 201
Parent Material ............................... 205
Climate ....................................... 206
Relief ........................................ 207
Plants and Animals ............................ 208
Time ...... 209
Selected Bibliography ......................... 211

CHAPTER 9: Vegetation Information for Coastal Georgia ........ 213
The Importance and Use of Vegetation
Information ................................... 213
Vegetation Information Available for
Coastal Georgia ............................... 220
Selected Bibliography ......................... 222

CHAPTER 10: The Marshes ....................................... 223
Formation and Sediment Characteristics ........ 223
Vegetation .................................... 226
Marsh Fauna ................................... 234
Primary Production ............................ 248
Energy Flow and Food Webs ..................... 251

PAGE

CHAPTER 11: The Open Marine and Estuarine Waters ............... 257
Physical Characteristics ....................... 2.58
Fauna of Estuaries and Inshore Waters .......... 268
Fishery Resources of Estuaries and
Inshore Waters ................................. 280
Productivity and Energy Flow ................... 286
Bibliography from An Ecological Survey
of the Georgia Coast ............................. 297

LIST OF TABLES

PAGE

CHAPTER 3

3-1: Summary of Total Acreage.and Geologic-Ages of Georgia
Barrier Islands ................................. ! ........ 41
3-2: Physical Factors and Functional Responses of Seleq.ted
Coastal Communities ............................... * ...... 104

CHAPTER 5

5-1: Withdrawal Use of Water (Million Gallons per Day) by
Area Planning and Development Commission Region, Source,
and Principal Use, 1970 ................................. 156
5-2: Water Use for Public Water Supply, by Area Planning
and Development Commission, 1970 ......................... 157

CHAPTER 9

9-1: Vegetation As An Environmental Indicator ................ 216
9-2: Principal Factors Determing Plant - Animal Distribution .217

CHAPTER 10

10: Coastal Wetland Types Occurring on the Georgia Coast ..... 227
11: Relative Salt Tolerance of Some Plants Important in
the Coastal Marshes of Georgia ......
12: Some Naturally-Occurring Plants of Significance in
Waterfowl Management ..................................... 242
13: Summary of Energy Flow in the Salt Marsh ................. 254

CHAPTER 11

14: Epifauna Collected from Docks at Colonels Island
(North Newport River, St. Catherines Sound) ............. 272
15: Invertebrate Fauna of Sapelo and St. Catherines Sounds ... 274
16: Fish with Total Landings in Georgia of More than
1000 Pounds Per Year ...................................... 284
17: Common Salt Water Sport Fishes of Georgia ................ 287
18: Some Food Habits Studies of Common Estuarine Fishes ...... 293
19: Feeding Habits of Estuarine Fishes ....................... 295

LIST OF FIGURES

PAGE

CHAPTER 2

2-1: Basic Functions of a Beach-Sand Dune-Offshore
Sand Bar System ........................................... 15
2-2: Profiles of Shoreline Equilibriums ....................... 20
2-3: Sand Dune Stabilization with Vegetation .................. 21

CHAPTER 3

3-1: Geologic Ages of Barrier Islands ......................... 40
3-2: The Hydrologic Cycle on Coastal Islands .................. 44
3-3: Hypothetical Cross-Section of a Georgia., Cbastal Island...48
3-4: Hypothetical Cycling of Sedimentary Nutrients on
Coastal Islands .......................................... 64

CHAPTER 4

4-1: Energy Flow Relationships of River Swamp-River
Channel 122
4-2: Components of the River Swamp Ecosystem During Low
Water ................................................... 126
4-3: Components of the River Swamp Ecosystem During Flooding.127

CHAPTER 5

5-1: Distribution of Water in a Core of Earth ................ 138
5-2: Generalized Ground Water Flow in a Water Table Aquifer..140
5-3: General Ground Water Flow in an Artesian Aquifer ........ 141
5-4: Effect on Local Water Table of Pumping a Well ........... 143
5-5: Idealized Cross Section from Macon to Brunswick ......... 145
5-6: Aerial Extent of the Potential Shallow Sand and
Gravel Aquifer ........... * .............................. 147
5-7a: Areal Extent of the Principal Artesian Aquifer and
Direction of Ground Water Movement ........ o ............. 148
5-7b: Depth to the Top of the Principal Artesian Aquifer
in Coastal Georgia ...................................... 149
5-8: Recharge to an Artesian Aquifer ......................... 150
5-9a: Water Level in the Principal Artesian Aquifer, 1880.....152
5-9b: Water Level in the Principal Artesian Aquifer, 1971 ..... 153
5-10: Cone of Depression in an Artesian Aquifer ............... 160
5-11: Diagram of the Brunswick Intrusion Problem ......... o .... 161
5-12: Diagram of the Salt-Water Intrusion Problem
at Savannah ............................................. 162
5-13: Rate of Ground Water Movement Toward a Cone of
Depression... ........................................... 164

PAGE

CHAPTER 10

27: Typical Profile of a Salt Marsh Showing the Marsh
Types Described by Teal, 1958 ............................ 232
28: Very Generalized Diagram of Production and Utilization
of Organic Matter in the Salt Marsh ...................... 252

CHAPTER 11

29: Bottom Topography of the Continental Shelf Off Georgia ... 259
30: Direction of Tidal Currents at Ebb and Flood Tides in
the Savannah Area as Predicted by a Physical Model ....... 263

CHAPTER 1

a Resource Planning Process
for
Georgia's Coast

Lillian F. Dean
Resource Planning Section
Office of Planning and Research
Department of Natural Resources

Purpose of Background Papers

Identification of the values and vulnerabilities of natural

resources is an important first step in resource planning.

Policies and programs for managing and utilizing resources

should be based upon such information. The purpose of these

background papers is to highlight important characteristics

of Georgia's coastal resource features and systems including

resource values and vulnerabilities.

A resource system is a unified physical or biological

environment that is characterized by interacting features and

subcomponents and dynamic flows. Beaches, sand dunes and

offshore sand bars, for example, are classified as a system

because of the dynamic sand flows that link the individual

subcomponents of the system together. A resource feature is a

single characteristi c of the environment that can be displayed

on a map. Resource features, such as soils, vegetation, and

topography,are important elements of resource systems.

An individual background paper has been written for eaCh

of the following systems and features:

Coastal Resources Systems:

Coastal Beaches, Sand Dunes and Offshore Sand Bars

Coastal Island Ecosystems

Fresh Water Ecosystems

Ground Water Conditions (aquifers)

Coastal Marshlands (excerpted from An Ecological
Survey of the Coastal Region of Georgia, with permission)

Estuarine and Open Marine Waters (excerpted from An
Ecological Survey of the Coastal Re ion of Georgia,
with permission)

Coastal Resource Features:

Soils

Vegetation

Wildlife

Cultural Resources (Historical and Archaeological)

Although separated into individual papers, many of these resource

systems and features are interrelated.

A Resource Assessment for Georgia's Coast

In order to assess the importance of natural resources,

as well as the conflicts and compatibilities between man's

activities and coastal resources@ coastal natural resource.

planning is being undertaken by the Georgia Department of

Natural Resources, in cooperation with other federal, State

and local agencies participating in the Coastal Zone Management

Program. The purpose of resource assessment is to provide

background information on natural resource capabilities and

on the environmental impact of proposed activities. This

information is essential for the development of coastal

policies and programs.

Resource analysis terms must be defined carefully before

tLey can be used. The following definitions are being used

in coastal resource assessment:

Value - The contribution of an ecosystem or resource
feature to the cultural or biological
environment, especially contributions which
affect the public health, safety and welfare.

Vulnerability - The natural sensitivity or suscepti-
bility of an ecosystem or resource feature
to change,

Capability (also called carrying capacity) - The ability
of an ecosystem or resource feature to support
a particular use or activity, based upon the
natural characteristics of the resource.

Environmental impact - The type of change in the eco-
system or resource feature caused by a specific
use or activity.

Compatibility - The degree to which two activities or
uses can co-exist in harmony with each other.

Suitability - The appropriateness of a proposed
activity for a particular resource or location,
based upon a variety of factors. (Usually
these factors include social, political, and
economic considerations, as well as natural
resource considerations.)

These terms, in turn, help to define the steps in a resource

assessment process.

Step 1 - Assessment of Value: An important prerequisite

to the development of plans and programs is an identification

and understanding of the multiple values of coastal ecosystems

and resource features. As expressed in the Congressional findings

of the Coastal Zone Management Act, "the coastal zone is rich

in a variety of ... resources that are of value to the present

and future well-being of the Nation." An understanding of the

value of resources to the health, safety and welfare of Georgia

citizens leads in turn to an understanding of why management

of the resource by various levels of government is important.

Although values may be defined in both quantitative and

qualitative terms, descriptive qualitative terms are commonly

used due to a lack of information about dollar values.

Step 2 - Assessment of Vulnerability: Vulnerability

factors relate to the basic forces that provide energy to the

ecosystem. They are the "lifelines" of the ecosystem, without

which the system would not exist. Hence they provide essential

information for capability analysis and environmental impact

assessment. They are def ined in natural terms, without a

specific use or activity in mind. Information on ecosystem

vulnerability can be interpreted most readily from scientific

reports.

Step 3 - Capability Analysis (or Carrying Capacity): The

most difficult step in a resource assessment process is the

identification of the ability of tl:e resource to support a

particular activity. Extremely fragile resources can support

only a few "low-impact" activities without causing great changes

in the system. Other resources can sustain a wide variety of

activities.

Important prerequisites for a capability analysis are:

(1) a precise definition of the use or activity being considered;

(2) information about resource vulnerabilities; and (3) an under-

standing of how resource features can be displayed on a map to

reflect vulnerabilities. The capability analysis is an assess-

ment of the amount and type of certain activities which can

be supported without changing the ecosystem. Capability analysis

can greatly assist the appraisal of environmental impact. In

turn, any information available on environmental impacts contri-

butes to capability analysis.

Step 4 - Environmental Impact Assessment: Information

concerning the values and vulnerabilities of coastal ecosystems

and the capability of natural resources to support various

activities is useful in evaluating environmental impact. The

accuracy of the environmental impact assessment is determined

by the accuracy of the information on vulnerability and capability.

A variety of methodologies for assessing environmental

impacts have been used in the past, such as checklists, computer

models, matrices and networks and map overlays. The particular

method to be used should be selected carefully, bearing in mind

available time, funding and information. The impact assessment

identifies zhe nature of changes in resource.systems or resource

features which will be caused by the proposed activity. The impact

assessment does not evaluate the significance of these impacts.

.SteT) 5 - Compatibility Analysis: The degree to which two

activities or uses can co-exist in harmony depends upon the

environmental impact of each activity. If one activity destroys

the resource base upon which another activity depends, then the

two activities are not compatible. For a comprehensive compati-

bility analysis, the social, economic and political factors

which affect activities (in addition to environmental factors)

should be considered. In fragile resource areas, such as coastal

marshlands or beach and sand dune systems, natural resource factors

play the major role in determining compatibility. In essence,

capability becomes equivalent to compatibility, since uses which

destroy the resource itself are not compatible with other uses

which depend upon the resource base.

Step 6_- Suitability Analysis: The appropriateness of a

proposed activity for a particular location should be determined

from a variety of factors. Capability analysis (as described

above) is in fact "natural" suitability. For a complete suita-

bility analysis, additional factors, such as economic demand for

certain activities, existing community uses and activities and

community goals,should be considered. The criteria that are used

in determining suitability should be established inan open forum

where many persons and groups may participate.

Resource Policiesand Programs

All of the steps in resource planning, as outlined above,

provide information useful in developing policies and programs

for coastal resources. The steps of the analysis also provide

a factual basis for comparing alternative plans and programs.

Information about the capability of resources to sustain
certain uses, the compatibility of resource uses with each
other, and the suitability of proposed resource uses for parti-
cular locations (according to a variety of criteria) is especially

useful for developing policies for the use and conservation of

natural resources. However, these analyses are difficult to

accomplish without acareful consideration of resource values and

vulnerabilities.

A major purpose of this report is to make inkormation on

resource values and vulnerabilities readily available to interested

officials and citizens. These papers summarize more lengthy

research reports and books, but contain selected bibliographies

for the reader interested in more detailed information about a

particular subject.

Management programs must be based upon an understanding of

resource values and vulnerabilities. A wealth of information

currently exists for the development of policies and programs

for coastal Georgia. However, all policies must be periodically

re-evaluated to incorporate new information and new societal

values.

CHAPTER 2

the Value and Vulnerability
of Coastal Beaches,
Sand Dunes, and
Offshore Sand Bars

George F. Oertel
Skidaway Institute of Oceanography

Introduction

Coastal dunes, beaches and offshore sand bars are all pari

.of an interacting and interdependent sedimentary environment.

Each of these areas is a separate sub-environment but each is

also dependent upon the two other parts of the system. In this

summary the terms beach, dune, offshore sand bars and shoals

will be used as defined below.

Beach - The relatively thick prism of loose sediment,

predominantly sand, located between the limits of lowest low

water and highest high water.

Coastal dunes - Mounds of sand deposited along a coastline

by eolian processes and often covered with sparse pioneer vege-

tation. Coastal dunes are located landward of the lim.its of

highest high water and may extend into the tree line.

Primary dune ridge - The most seaward continuous dune ridge

running generally parallel to the shoreline.

Foredunes - Individual mounds of sand located seaward of the

primary dune ridge.

Semi-stable dunes - A variety of coastal dunes located

between highest high water line and the tree line. Mounds in

this zone are subject to periodic erosion by storm waves and

rebuilding by eolian processes.

Stable dunes - A variety of coastal dunes that have been

stabilized in position by a dense vegetative cover. These

dunes are generally located landward of the semi-stable dunes.

Offshore sand bars - Mounds of sand deposited by the

action of waves and currents. This sand moves up the beach slope

in response to wave action. Offshore bars are emerged during low

tide and submerged at high tide.

Offshore shoals - Submerged mounds of sediment that are

elevated above the surroundinL surface of the ocean floor. In

this report they are defined as extending from -12 feet (mean

low water) to mean.low water.

Since the dunes, beaches, and offshore bars are all part

of an interdependent sediment SyStEM, the system will be

referred to as the dune-beach-bar system within this technical

summary.

The extent of the dune-beach-bar system is variable, depending

on its location along the Georgia shoreline. In some eroding

areas there are no semi-stable dunes; only narrow beaches, and a

few small offshore bars. In other areas, zones of semi-stable

dunes are over 1000 feet wide, beaches are over 400 feet

wide, and large areas of offshore bars are over 3000 feet

from the shoreline. In general, these extremes are local

in occurrence and a complete gradient exists in between.

Nature of Existing Information

Information on the dunes, beachE'-s and offshore bars of

the Georgia coast is scant. This is becau-se much of the exist-

ing generalized information on dunes, beaches and offshore bars

may not apply to the unique Georgian environment. Some of

the parameters characterizing this environment include: 1) a

broad shallow Continental Shelf; 2) relatively low wave energy;

3) moderately high tidal ranges; 4) numerous islands and inlets;

and, 5) a large semi-diurnal exchange of water between marsh-

lagoons and shelf waters. Mu,z!h of the early research neglected

these parameters and for this reason it is not entirely appli-

cable. Presently portions of the University System of Georgia

are conducting research on the interrelationships between

offshore bars and distributions of wave energy. The study of

processes relating sediment transfer between Georgia dunes,

beaches and bars is also still in the initial research stages.

The areas adjacent to Tybee Island and Sapelo Island have

received the most research attention because of their proximity

to the Oceanographic Institute and the Marine Institute.

Reports on the Tybee work are available through the Marine

Extension Service on Skidaway Island, whereas, the reports of

work conducted on and adjacent to Sapelo Island may be found in

the collected reprint file of the Marine Institute on Sapelo

Island. Selected scientific publications by John Hoyt, V. J.

Henry, J. D. Howard and G. F., Oertel are also sources from

which valuable information can be extracted.

Although a good deal of data is available, much of it has

been obtained in order to answer some specific scientific question.

Relating this information to assessment of the value, sensitivity

and vulnerability of an ecosystem is difficult. Initially, environ-

mental inventories must be made to determine the natural or present

condition of the system. In some cases, this may involve detailed

surveys on.numerous critical parameters, as has been and is being

done in the marshlands. Process studies for the shorelines are

also required, for erosion and accretion are natural phenomena

that apparently vary for each of the Georgia islands.

The Value of Dunes, Beaches and Offshore Bars

Dunes, beaches and offshore bars are valuable to many facets

of the environment. To thoroughly evaluate the true value of

these areas, we must consider them in terms of education, aesthe-

tics, ecology, recreation, tourism, sedimentology and property.

Many of these values are interrelated and, as such, are often

confused. While this report is intended to outline only

the sedimentologic value of dunes, beaches and offshore bars,

a few examples of other types of values may serve for purposes

of clarification.

Ecologicallythe dunes serve as nesting grounds for turtles

and numerous species of birds. Numerous other animals live,

hunt and graze in the dunes. The beaches and offshore bars are

dwelling sites for polychetes, sand shrimp and various isopods,

decapods, bivalves and gastropods.

Aesthetically, the dunes, beaches and offshore bars offer
an unlimited wealth to artists, photographers ar@d writers. The

flowing lines of the dunes capped by sea oats, the beach with

racks of straw, and the white water over offshore bars have pro-

duced pleasing subjects for many local artists. Every year

thousands of Georgians and other tourists also visit the shore

to enjoy this beautiful natural setting.

Educationally, the dunes, beaches and bars are a natural

classroom for geologic and ecological processes. The rela-

tionships and dependencies are easily seen between plant life

and animal life in the dunes, beaches and bars. The Savannah

Science Museum, the Georgia Conservancy, the Georgia Geological

Society, and portions of the University System of Georgia have

repeatedly visited the shoreline to describe the various physi-

cal and ecological processes of the area.

Recreationally, the shoreline serves large portions of

the local population for boating, bathing, surfing, sunning, etc.

These activities apparently play an important role in relieving

the social pressures of urban living.

All of the values described above enhance the tourist value

of the dunes, beaches and bars. Tourists are generally attracted

to the shoreline because of the aesthetic and recreational value

of this area; however, their activities on the shoreline often

result in a better understanding of the local ecology. Tourist

and recreational activities also often put stresses on the ecologi-

cal and sedimentol6gical functions of the shoreline. For this

reason, planning and management programs for protecting these sys-

tems are important for the future.

From a sedimentologic point of view, the dune-beach-bar

systems of Georgia are valuable for at least three major reasons

(see Figure 2-1). First, the system is a barrier that protects

land behind it. Second, the system maintains a sediment budget

that determines the stability of the shoreline. Third, the system

dissipates the energy of major storm waves before the total energy

of these waves can be directed at the property above the beach.

The Barriers: Although offshore shoals and bars are not

present along the entire Georgia shoreline, there are some areas

of shoreline that illustrate extensive system of offshore shoals

and bars. These shoals and bars are the initial barriers to high

energy storm waves and much of the wave energy is diverted as waves

collide with these bars. In response to this diversion of wave

energy bythe sand bars, sediment is often redistributed over the

surface of the bar by wave currents.

Figure 2-1

Basic Functions of a
Beach- Sand Dune- Offshore Sand Bar System

As illustrated in the three diagrams below, the Beach - Sand
Dune - Offshore Sand Bar System serves three basic functions.
(A), the system serves as a barrier to high energy storm waves;
(B), the system dissipates the force and energy of waves as they
move shoreward; (C), the system maintains a sediment budget
that determines the stability of the shoreline.

(A) Barriers:

last coastal barriers secondary primary
dune barrier barrier
fore- beach
dunes offshore
bar

(B)Energy Disipators: low energy swash currents
moderate high energy
energy breakers point of waves
energy transfer
terminal
energy loss 2nd
energy offshore
transfer bar
dunes beach

(C) Sediment Sharing:
backshore offshore
semi sediment sediment
stable stable reservoir reservoir
dune dune fore- low energy
ridge ridge dunes profile
storm profile offshore
dunes beach bar

Source: G. F. Oertel.

The beach is the second barrier to high energy storm waves.

After some of the wave energy is diverted by moving across the

sand bars, the waves collide with beach. Since beaches are

inclined surfaces and waves generally approach at some angle to

the shoreline, wave energy is redirected along the shoreline in

the form of a longshore current.
During large storm surges, the dunes often function as the

last barrier to the sea. If this barrier is destroyed, then

the land and structures behind it may be inundated by flood

waters and storm waves. This last barrier also redirects the

energy of storm waves in an offshore direction or in an along-

shore direction. The redirection of wave energy by the dune

barriers generally results in the longshore flow of water.

Energy Dissipation: The dunes, beaches and offshore bars

are also natural devices that dissipate wave energy as waves

move landward. As described above, a portion of the wave

energy is redirected parallel to the shoreline when it inter-

acts with the offshore bars. As waves cross over offshore

bars, a portion of the wave energy is also transferred into

the mobile sediment bed on the shoal surface. This transfer

produces a temporary suspension of sediment above the bottom

and a redistribution of sediment over the surface of the bar.

Redistributed sediment is often transported landward, thus

producing landward displacement of the bar.

When waves are squeezed into the shallower water over

shoals, some of the waves "break" at the surface and

some wave energy is dissipated. The loss of energy is often

illustrated by white water or "white caps" along the crests

of waves. This is one reason why shorelines that are protected

by massive offshore shoal and bar systems appear to suffer less

erosion during storms than shorelines that are exposed to the

direct attack of waves.

The beach is the second major portion of the energy

dissipating zone of the shorel-f"ne. As noted above, beaches

are inclined surfaces, and as waves move up this inclined sur-
face, the orbital motion of water in waves is t@ansferred to a

lateral motion (current). As a result of this transfer, some

wave energy is lost and the force of the waves is somewhat

diminished. The dissipation of wave energy at the beach is

easily observed as "rolling" waves are transformed into

"breaking" waves. The resultant longshore current often

carries a relatively large load of sand parallel to the beach.

The periodic breaking of waves at the beach slope (swash)

and then rush back down the beach slope (backwash).

During very large storms, breaking waves may extend up

into the dunes and swash currents may flow up the dune slopes.

Waves that reach the dunes are channeled through, over and

around foredunes. The rerouting of water through this intri-

cate maze of foredunes further slows the water and dissipates

the eroding ability of the waves. The primary dune ridge,

located landward of the foredunes, is a barrier to storm

wave surges all along the shoreline. When the waves collide

with the primary dune ridge, water rushes up the dune slope and

then slides back down. This dissipates wave energy further and

most of the wave surge is redirected seaward.

The Sediment Budget: The dunes, beaches and offshore

shoals and bars also maintain a sediment budget that determines

the stability of the shoreline. When a sediment deficit is

produced in this budget, the shoreline retreats by erosion.

When a sediment excess is produced, the shoreline advances

seaward by accretion.

At a stable shoreline, processes of both erosion and accre-

tion maintain a dynamic equilibrium in the sediment budget.

For example, during portions of the year, erosional processes

may cause the shoreline to retreat; however, during otherpor-

tions of the year, depositional processes cause the shoreline

to advance seaward. The net change in shoreline position after

a complete year is often negligible,and the location of the

shoreline remains stable on a year to year basis. Sedimentary

processes governing this equilibrium involve sediment transfers

between the dunes, beaches and offshore bars. The "sand-sharing"

capabilities of each of these s ub- environments are critical to

maintain the stability of the shoreline.

Each of these sub-environments undergoes a sequence of

sedimentary events during storm conditions and low energy

conditions. During low energy conditions, offshore bars migrate

landward. Low energy, long-period waves redistribute sediment

over the surface of the bars in a semi-continuous movement up

the beach slope. This results in the barst attachment to the

uppermost portion of the beach. As more bars are "welded"

to the upper sections of the beach, the beach accretes seaward

to produce a broad, low-elevation, high-tide beach. During

storm conditions, the beach face is eroded and a part of the

sediment from the beach is transported seaward toward the

offshore bars. This redistribution of sediment or "sharing"

is necessary to maintain the stability of the shoreline.

It is also apparent from these processes that the beach

and nearshore zones have different profiles of equilibrium

during low energy conditions and during storm conditions. The

realization that the beach and. nearshore topography adjust

to the local energy conditions is very important for considering

the effects of various stresses on the system. For example,

the beach profile adjacent to a channel with high velocity

currents is steep, whE@reas the profile adjacent to a channel

with low velocity currents is gentle. Since the profile is in

equilibrium with the velocity of water flowing through the

channel, the channel will adjust to the pre-dredging form in

order to achieve equilibrium conditions between energy and

topography (see Figure 2-2). This adjustment will, in turn,

result in a lowering of the adjacent beach profile.

A sediment-sharing relationship also exists between the

beaches and the semi-stable dunes. During low-energy condi-

tions when the beach is broad, the dry sand on the high tide

Figure 2-2
Profiles of Shoreline Equilibriums

68orna-phic- Ecpilibr@urn - low veJwiA

Oe=cr@t Eqwilibrk"- hiqh veJod@ (Y,@..X)

-es nrq

. .. ... .... ...

. ..... ..

Oeomorphic In5tabild-H (Y>x)

. . . . . . . . .....

volurw-

F. Oertel.

Figure 2- 3
Sand Dune Stabilization with Vegetation

SURFACE

SAND SURFACE

SAND
�URFACE

Dune vegetation such as sea oats (Uniola Paniculata) binds
F@
sand through the development of extensive ord-zontal and
vertical rhizome systems.

Source: Based on diagram in D. S. Ranwell, Ecology of Salt
Marshes and Sand Dunes, Halsted Press, 1973.

portion of the beach is transported by the winds. When the

winds are offshore, sand is transported down the beach slope

and into nearshore waters where it is deposited or redistri-

buted by nearshore currents. When winds are in an onshore

direction, sand is transported up the beach face and is often

deposited in the dunes. This process also affects the incipient

development of new dunes. Mounds of beach straw that accumu-

late behind the spring tide berm are obstructions that disrupt

the lamina flow of air over the beach. As wind-blown sand

comes into contact with these obstacles, a portion of the

sediment is deposited in the straw mounds. These accumulations

of sand increase in size with time and form small foredunes.

Eventually, the sand may completely bury the straw mounds that

initiated their development. The proximity of these foredunes

to the sea deems them very vulnerable to erosion during even

very minor storms. If the shoreline is relatively stable, then

pioneer plants may spread into these dunes by rhizomatous

development or seed growth. The organic material buried in

the dunes holds moisture and supplies nutrients to seedlings.

Relatively large plants that grow from the seedlings form

new wind baffles. These baffles disrupt the air flow in a

manner similar to that described for the straw mounds; however,

the plants are higher and disrupt more of the air flow. This

process produces more deposition of sand and accelerates

expansion of the foredunes. The accumulation of sand by this

process makes it less likely that foredunes would be completely

destroyed during minor storms. If this process is left to

continue with only minor interruptions, foredunes may

coalesce and form a continuous dune ridge. Tall grasses and

large plants form the vegetative caps of these ridges, and

enhance the entrapment of much of the remaining sand that is

in windblown transport up the beach. The root systems of the

grasses and plants also function as holdfasts that partially

secure the dunes and help to bind the loosely packed sand

grains together. The final result of the sediment-trapping

processes is the accumulation of relatively large quantities

of sand above the spring high-tide line.

During high energystorm conditions, the beach face is

lowered as sediment is transported offshore into bars.

The lowering of the beach face a--so results in the retreat of

the shoreline. Eventually storm waves begin to attack the

berm and structures located progressively landward of the berm,

such as the mounds of straw and sand, the plant-covered fore-

dunes and the dune ridges. Sediment eroded from these struc-

tures can minimize the losses from the beach. The concept of

the equilibrium profile is also in effect in this zone. During

a storm, the equilibrium profile of the beach gets steeper as

the energy increases and sediment is transported offshore.

This adjustment often causes the shoreline to retreat and the

dune to erode. Sediment from the dunes is temporarily trans-

ported to sedimeftt-poor portions of the beach that have

suffered from severe erosion. In minor storms, sand from the

foredunes and from a portion of the primary dune ridge is often

redistributed over the beach surface. In major storms, the

entire sediment reserves of the primary dune ridge and a por-

tion of the second dune ridge may be redistributed over the

beach face. Sediments from each successive dune ridge are

redistributed over the beach face as is required by the "sand-

borrowing" system between the beach and the dunes. Thus the

sand-borrowing system helps to maintain a profile of equili-

brium at the beach without an accelerated retreat of the shore-

line. After storms subside, sedimentary processes begin to,

restore the dune-beach-bar system to a profile of equilibrium

that is quasi-stable with daily low energy conditions. These

processes reconstruct the beach and dunes and prepare it for

the next series of storms.

Critical Features

There are a number of features that are critical to the

functioning of the dune-beach-bar system. Dune plants are one

of the more obvious features. If these plants are destroyed,

the accumulation of sand in coastal dunes is inhibited and the

recovery of dunes between storms is slowed down considerably

(see Figure 2-3).The stabilizing function of plant roots is

also critical for inhibiting the migration of dunes. Dunes

that are not partially stabilized by vegetation may migrate

considerable distances in response to winds. The migration of

dunes could in fact cause the burial of large structures

located down wind of dunes.

The shapes of dunes and offshore sand bars also have a

considerable impact.upon the function of the dune-beach-bar

system. The efficiency that a barrier has in protecting struc-

tures behind it is dependent upon its height, strength, and

continuity. If dunes and bars are reduced in height, their

effectiveness as a barrier is reduced. If the continuous

nature of a dune ridge is breached by a path or roadway, storm

surges can flow through these breaks and endanger structures

behind the ridges. Breaks also permit winds to transport

tongue-shaped dunes landward of the dune ridges., These tongue-

shaped dunes also present burial hazards to the structures

behind the dune ridges.

The shapes of offshore bars and shoals are also important

since they often determine the paths of tidal flow and ulti-

mately of sediment transport. For example, if the shape of a

shoal is altered in a manner such that it redirects current

energy, then sediment transport patterns are also likely to be

altered. The final result could potentially cause the shifting

of a navigational channel, or the accelerated erosion or accre-

tion of adjacent areas of beach. The response to changes in the

shapes of sand bars and shoals, would be quite variable with

actual changes depending on the specific case. However, it is

important to note that the geomorphic character of offshore

sand bars and shoals is a feature that is critical to ihe

functioning of this portion of the system. In th is regard, the

3hape of the bars and shoals must be considered in view of its

effect on the function of these sand bodies as potential barriers,
energy dissipators, sediment reservoirs and as a pathway for
controlling the distribution of tidal energy.

There are several criteria that are very important to the

functioning of the dune-beach-bar system. One criterion is

the unhampered exchange of sediment among all parts of the

system. If barriers are established restricting the exchange

of sediment and wave and current energy between portions of

the system, then the efficiency of the system is endangered.

The unhampered exchange of sediment between all parts of the

system is of particular importance to the interrelated functions

of the dunes, beaches and barts described above.

Sensitivity and Vulnerability

The dune-beach-bar system is self-adjusting to small

changes in physiography, sediment input and energy distribution.

This coastal sediment system is relatively sensitive to change

and responses can be seen in physiographic adjustments.

The type of stresses which affect the functioning of the

dune-beach-bar system are closely related to the critical

features described above. The most obvious stresses on the

system are the periodic increases in physical energy due to

storms. These increases may produce very radical changes in

the shoreline; however, much of the original form of the shore-

line may be restored during low energy conditions. In general,

storms produce only short term modifications to the shoreline;

however, locally, long term modifications are produced by large

'MJ%

storms. A good deal of the recovery process is dependent upon

the unimpeded transport of sediment by natural processes. Sea-

walls, groins, dredging and channeling are all stresses which

impede the transport of sediment by natural processes. Each

of these stresses has a different impact,on the system and the

system adjusts in a different manner to each type of stress.

For example, groins entrap sediment on their updrift sides- and

produce erosion on their downdrift sides. Eventually the shape

of the shoreline will come into equilibrium with these obstruc-

tions and new routes of sediment transport along the beach will

result.

While seawalls protect lowland areas from storm waves,

they also restrict the exchange of sediment between the beaches

and dunes and in this regard they also inhibit recovery of

sediment to a storm-eroded beach. Seawalls also reflect much

of the energy from storm waves directly back toward the beach.

These high energy waves redirected toward the beach without much

energy loss may accelerate the erosion of the adjacent beach

until a new equilibrium profile is created for the new energy

condition. In many cases, both groins and seawalls are effec-

tive methods of stabilizing pcrtions of beach, however, their

design and installation must be considered carefully. Design

and installation must be effected in a manner to produce stress

on the mechanisms of erosion with as little impact as possible

on the functIoning of the ecosystem. In general, an area of

shoreline erodes because of some imbalance in the energy-sedi-

ment budget. Groins and seawalls cannot solve the problem

because they generally do not balance the budget.

Dredging and channeling are also stresses that may affect

the system. These activities may take sediment out of the

system, change shoreline profiles and produce a redistribution

of wave and current energy. The degree of influence produced

by this type of activity is dependent upon the magnitude of

the activity. The construction of an extremely large channel

or hole adjacent to a beach could have extensive erosive effects

upon the offshore shoals and the shoreline. In order to adjust

to the previous profile of equilibrium, sediment from the ad3'a-

cent shoreline may be transported into the channel.

The creation of deep water adjacent to a previously shallow

water shoreline allows high energy waves to collide witt. the

shoreline before any energy can be dissipated on sand bars and

shoals. The redistribution of water flow through dredged

channels also may form new sediment transport patterns and cause

-shifting of offshore shoals and bars. Ultimately these adjust-

ments may influence the sediment budget of adjacent areas of

shoreline and produce new erosion and accretion trends.

The dunes are also vulnerable to stresses that affect the

functioning of the system. The active portion of the dunes plays

a very important role in the functioning of the dune-beach-bar

system. If the natural shapes of these dunes or the interdepen-

dent plant species of these dunes are destroyed, then the dunes

may be destroyed. In general, the natural characteristics of the

active portions of.the dune system must be preserved in order for

the dunes to function in the ecosystem.

A Buffer Zone

A buffer zone necessary to protect the various components

of the dune-beach-bar system is difficult to define for the

Georgia coast because of the extreme variability of the system's

characteristics. In general, the buffer zone should be located

on the landward margin of the beach and on the seaward side

of the offshore shoals and bars.

While the width of buffer zone landward of the dunes

cannot be defined uniformly for all areas of the coast, the

relationship of the dunes to t-he sedimentary activity of the

system can be used to,,develop general guidelines. The buffer

zone for the dunes is variable along the length of the shore

and is dependent upon the long range fluctuations of the shore-

line, and the seasonal fluctuations of dune character. On

stable or accreting shorelines, the buffer zone should extend

to at least halfway between the first and second continuous and

semi-stable dune ridges landward of the ocean. In historically

retreating or unstable areas, the width of the buffer zone

should be based upon the 100 year rate of shoreline retreat

and the seasonal variability of the shoreline and dune ridges.

The buffer zone for offshore bars and offshore shoals is

probably the most difficult to define because relatively little

is known of the processes of sediment transfer between these

features and the beach. Offshore bars often play an important

role in the exchange of sediment between the nearshore and the

beach, thus, all offshore bars in the intertidal zone should

certainly be encompassed within the buffer zone. Around tidal

inlets, shoals from 0 feet to -12feet also play important roles

in transferring sediment between the inshore zone and the beach.

Tidal currents and wave currents are the major mechanisms of

sediment transport at these shoals. If the paths of these cur-

rents are in some way altered, then the natural exchange of

sand between the offshore and the beach could be impeded or tem-

porarily delayed. The area outlined by the -12 foot (mlw)

contour should be considered relatively important in defining a

buffer zone for the seaward limit of the dune-beach-bar system.

Although this eliminates most of the Georgian inlets (because

they are greater than 12 feet deep) it must be realized that

extreme increases of inlet volumes would have an adverse effect

on the stability of the -12 foot surface. The adjustment of

inlet volumes by dredging must be considered in the light of

the natural profiles of equilibrium for the area.

SELECTED BIBLIOGRAPHY

Brunn, P. and Battjes, J. A., 1963, Tidal inlets and littoral
drift, in Recent research in coastal hydrolics: London,
InternaT.- Assoc. Hydrolic Research, 10th Cong., Proc.,
Vol. 1, p. 123-130.

Brunn, P. and Gerritsen, F., 1959, Natural by-passing of sand at
-coastal inlets: Amer. Soc. of Civil Engineers Proc., Vol.
85, Paper 2301, Jour. Waterways and Harbors Div., no. WW4
pt. 1, p. 75-107.

Davis, R. A., and Fox, W. T., 1972, Coastal processes and nearshore
sand bars: Jour. of Sedimentray Petrology, Vol. 42, p.
401-412.

Dolan, R., Godfrey, P. J., and Odum, W. E., 1973, Man's impact
on the barrier islands of North Carolina: Amer. Sci.,
Vol. 62, no. 2, p. 152-162.

Godfrey, P. J., and Godfrey, M. M., 1973, Comparison of ecological
and geomorphic interactions between altered and unaltered
barrier island systems in North Carolina in Coates, Donald
R., ed., Coastal geomorphology: Binghamt-on, New York,
State University of New Y:,,rk., p. 239-2S7.

Graetz, K. E., 1973, Seacoast plants of the Carolinas; Chapel
Hill, Univ. North Carolina, Sea Grant Pub. no..UNC-SG-73-06,
206 p.

Kaye, C. A., 1961, Shore-erosion study of the coasts of Georgia
and northwest Florida: U. S. Geol. Survey Dept. for U. S.
Study Comm., Southeast River Basins, 74 p.

Kurz, H., 1942, Florida dunes and scrub, vegetation and geology:
Florida Geological Survey Bulletin 23, 154 p.

Land, L. S., 1964, Eolian cross-bedding in the beach dune
environment, Sapelo Island, Georgia: Jour. Sedimentarv
PetrologV, Vol. 34, p. 389-394.

Larsen, M., and Oertel, G. F., In preparation, Zonations in
coastal dunes and distribution of dune plants.

O'Brien, M. P., 1931, Estuary tidal prisms related to entrance
areas: Civil Eng., Easton, Pa., Vol. 1, p. 738-739.

----- 1969, Equilibrium flow areas of inlets on sand coasts: NewYork,
Amer. Soc. of Civil Engineers Proc., Vol. 95, Jour. Waterways
and Harbors Div., no. WW1, p. 43-52.

Oertel, G. F., 1971, Sediment'-hydrodynamic interrelationships at
the entrance of the Doboy Sound Estuary, Sapelo Island,
Georgia, Unpub. Ph.D. Dissertation, Univ. Iowa, Iowa City,
Iowa, 172 p.

-.----1973, Observations of net shoreline positions and approxi-
mations of barrier island sediment budgets: Georgia Marine
Science Center, Tech. Report 73-2, 23 p.

---- 1974a, A review of the sedimentological role of dunes in
shoreline stability, Georgia coast: Bull. Georgia Acad.
Science, Vol. 32, p. 48-56.

----- 1974b, Hydrographic framework of the Doboy Sound Estuary
and surveys of the other tidal inlets along the coast of
Georgia: Georgia Marine Science Center, Tech. Report 74-4,
61 p.

----- 1974c, Patterns of water flow and sediment dispersion
adjacent to an eroding barrier island: Georgia Marine Science
Center, Tech. Report 74-2, 88 p.

----- 1974d, Residual currents and sediment exchange between estuar-
ine margins and the inner shelf, southeast coast of the
United States, in Symposium Volume for the International
Symposium on In@F_errelationships of Estuarine and Continental
Shelf Sedimentation, Bordeaux, France. p. 135-143.

Price, W. A., 1963, Patterns of flow and channeling irl tidal
inlets [Abs]: American Association of Petroleum Geologists
Bull., Vol. 47, no. 2, p. 366-367.
Savage, R. P., 1963, Experimental study of dune building with
sand fences in Coastal Engineering, 8th Conf., Mexico City,
Proc., Richmond, Calif., Council Wave Research, Eng. Found.,
p. 380-396.
Savage, R. P.,and Woodhouse, W. W., Jr., 1968, Creation and stabili-
zation of coastal barrier dunes: llth Conf. on Coastal
Engineering, Am. Soc. Civil Eng., New York, New York, Proc.)
Vol. 1. p. 671-700.
Stapor, F., 1973, History and sand budgets of the barrier island
system in the Panama City, Florida, region: Marine Geology,
Vol. 14, p. 277-286.
Todd, T. W.5 1968, Dynamic diversion - influence of longshore current-
tidal flow interaction on chenier and barrier island plains:
Jour. Sedimentary Petrology, Vol. 38, p. 734-746.

Woodhouse, W. W., and Haines, R. E., 1967, Dune stabilization
with vegetation on the outer banks of North Carolina:
U. S. Department of the Army, Corps of Engineers, Coastal
Engineering Research Center, Fort Belvoir, Virginia, Tech.
Memo. no. 22, p. 1-45.

Woodhouse, W. W., Seneca, E. D., and Cooper, A. W., 1968, The
use of sea oats for dune stabilization in the southeast:
Shore and Beach, Vol. 36, no. 2, p. 15.

CHAPTER 3

Terrestrial Ecology
of the
Georgia Barrier Islands

James I. Richardson
Department of Zoology
University of Georgia

and

Joanne S. Worthington
School of Forestry
University of Georgia

The Island Experience

A visitor, upon arriving for the first time on one of

Georgia's wild barrier islands, is immediately struck by a

feeling of isolation, a feeling that he has left the mainland

far behind and has entered another world. He iz probably

closer than he will ever be again, standing on the beach at

that moment, to sensing the real fabric of the island ecosystem.

The sculptured trees leading back from the dunes, the pounding

surf, the salt on his face left by the wind, the raccoon taking

one more egg from last night's turtle nest, all add to the

inescapable knowing that here is a world which has been born

. 35

of the physical forces which surround it.

The visitor is correct, for islands are different from the

mainland. Island communities are molded and remolded by the

winds, by the sand and salt, by the very isolation which makes

an island what it is. The tragedy is that man's emotions are

soon left to children and artists, and his priorities shaped by

his need for comfort. Our visitor will probably end his island

stay more annoyed by blowing sand which ruined his picnic lunch

than impressed by the dynamics of a dune community. He will

return home with a dose of chiggers and fail to support a

controversial environmental protection bill. When he again

returns to the island, he may find a comfortable ocean-front

motel but no dunes. He will find the ocean but perhaps no

beach. He may drive to his motel over a new causeway and not

visit an island at all.

At another time and another place, our friend might have

made his first visit to a Cumberland Island National Seashore

or the equivalent. Hopefully, he will still arrive by boat,

and his first impression will still be one of remoteness, of

island forests and pounding surf. His first view on the ocean

beach will be from a raised trail through sea oat dunes and not

from a car window. His lodging that night may be comfortable,

but it will not be a motel with a protective seawall. Most

important of all, his initial inspiration and curiosity will be

caught and reinforced by an interpretive.program of coastal

ecology, with all of its fascinating ramifications.

360

A knowledge of coastal ecology is essential for establish-

ing development guidelines and constraints, and for working
within the natural community without destroying its identify.

Our visitor may be one of several thousand to visit Cumberland

Island that day, yet his impression can still be one of isola-

tion and natural beauty. A knowledge of coastal island ecology

also has an important educational role. Strong supporters of

wilderness and open-space are often those who have learned to

read and enjoy a natural ecosystem as one would read and enjoy

a book. Awareness breeds appreciation and respect.

This paper summarizes what we know about the terrestrial
ecology of Georgia barrier islands, the physical environment

which shapes the\lisland community, and the strategies of

survival employed by its members. Also discussed are values of

component parts to the natural island system and the vulnera-

bility of the system to changes by man. The description of

terrestrial island ecology as a means of increasing man's

awareness of his environment is a self-evident value.

Physical Factors Shaping Coastal Island Ecology

A community develops in response to the forces which act

upon it. Some communities (deserts, tundra) must respond

primarily to physical forces such as extremes in temperature

and humidity. Other communities (tropical rain forest) develop

where physical forces are consistently optimum and respond

primarily to biotic forces which develop within the community.

Georgia coastal island communities fall somewhere between these

two extremes and respond to a variety of physical and biotic

forces. However, as one moves from the adjacent mainland to

large Pleistocene islands, and then to small Holocene islands,

there is a distinct shift in community structure in response to

the increasing intensity of several physical factors.

1. Geologic Factors

The geology of Georgia coastal islands has been summarized

by Hoyt (1967, 1968), although aspects of his thesis are

currently being debated. A number of specific points are

applicable to coastal ecology:

a) barrier islands are probably formed by dunes and

not off-shore bars. This is based on the observation that

the parent surface material of the islands is almost pure

quartz sand, with little clay, silt, or shell material.

The adjacent mainland consits of a variety of relic

lagoonal and barrier island complexes, adding diversity to

mainland soils relative to island soils.

b) the present coastal islands are of two historical

ages (Figure 3-1). The larger islands are primarily Pleistoi-

cene (25,000-30,000 BP) and have eroded over the years to

form a rather flat terrain. Eastward of this chain is a

second chain of smaller islands formed during the Holocene

(5000 BP to present). Additional material of Holocene

origin has also been deposited on the eastward or ocean

side of most Pleistocene islands. The topography of

OCLC: 9326916 Rec stat: n
Entered: 19830319 Replaced: 19950308 Used: 19950123
$ Type: a Bib Lvl: m Source: d Lang: eng
Repr: Enc LvL: I Conf pub: 0 Ctry: gau
Irdx: 0 Mod rec: Govt pub: Cont: b
Desc: a Int LvL: Festschr: 0 IlLus: a
F/B: 0 Dat tp: s Dates: 1975, %
$ 1 040 GUA Ic GUA %
$ 2 043 n-us-ga %
$ 3 090 HT393.G4 lb V340 %
$ 4 090 lb %
$ 5 049 NO@M %
$ 6 245 04 The Value and vulnerability of coastal resources : lb background
papers for review and discussion / Ic prepared by Resource Planning Section,
office of Planning and Research, Georgia Department of Natural Resources. %
$ 7 260 [AtLanta, Ga. : lb Dept. of Natural Resources], Ic 1975. %
$ 8 300 320 p. : lb RL. ; Ic 28 cm. %
$ 9 500 Papers written by individual scientists and researchers in the
University System of Georgia and in the Dept. of Natural Resources, for the
Georgia Coastal Zone Management Program. Cf. Letter from Joe D. Tamer,
Commissioner, on page preceding t.p. %
$ 10 Soo "Special assistance on this report was provided by the institute
of Natural Resources, University of Georgia.,, %
$ 11 504 includes bibliographies. %
$ 12 650 0 Coastal zone management Iz Georgia. %
$ 13 650 0 Conservation of natural resources Iz Georgia. %
$ 14 710 1 Georgia. lb Dept. of Natural Resources. %

Holocene formations consists of dune ridges and swales

that have changed little since the islands were formed.

Drainage patterns are highly dissected. The drainage on

dunes is very rapid. Soil conditions on Holocene forma-

tions are less developed (seedescription,of island soil).

c) there is a continual reworking (erosioh and deposi-

tion) of natural shorelines, differing in intensity from

island to, island, which can amount to the addition or

removal of hundreds of acres of elevated (above tidal

inundation) island terrain within a few years. Such

reworking affects both Holocene and Pleistocene formations.

Areas of recent deposition have virtually no soil profile

and are described and mapped as "coastal beach" (Wilkes,

et al.,1974-).

Twelve barrier islands are listed in Table 3-1, along with

estimates of total non-salt marsh acreage (Johnson,et al.,1971)

and a very rough approximation for each island of the percen-

tage of Holocene versus Pleistocene deposits, based on Figure 3-1

(Hoyt, 1968). Several observations can be made:

a) Pleistocene islands,, as used in this paper,

are barrier islands which consist roughly of fifty percent

or more of Pleistocene deposits, the remainder being Holo-

cene in origin. There are six islands in this category:

Cumberland Island, Jekyll Island, St. Simons Island, Sapelo

Island, St. Catherines Island, and Ossabaw Island.

b) Holocene islands, as used in this paper, are

Figure 3-1

Geologic Ages of tybec i--@and
Barrier lslaffds
Wa5SM i5l@d
49 Holocene deposits
(gPleistocene deposits aba
051@x w i5lmd

5t cztficrinc5 i516nd

Hackbe-ard i5lan

--aF)jeO bbrld

lit-He st simons i5lbnd

51ca j5Jand
5t t5irrX)n5 i5lorld

jekqll f--Jand

liftle 0-jr-nbe-ric-ind 1*eJ&-d

CUML>cHwid dard

0 10
L- I miles

Source: Hoyt, J. H., 1968, "Geology of the Golden Isles and
Lower Georgia Coastal Plain," in the Future of the
Marshlands and Sea Islands of Georgi . Edited by
D. S. Maney, F. C. Marland, and C. B. West. Published
by the University of Georgia Marine Institute and the
40 QAPDC. pp. 18-34.

Table 3-1

Summary of Total Acrea;@e and Geologic
Ages of Georgia Barrier Islands*

Island Total Acreage Holocene Pleistocene
(less than F20,000 to
5000 years) 40,000 years)

Pct. Acreage Pct. Acreage

Tybee 3,100 100% 3,100 0 0

Wassaw 2,500 100% 2,500 0 0

Ossabaw 11,800 50% 5,900 50% 5,900

St. Catherines. 7,200 40% 2,880 60% 4,320

Blackbeard 3,900 100% 3,900 0 0

Sapelo 10,900 10% 1,090 90% 9,810

Little St. Simons 2,300 100% 2,300 0 0

Sea Island 1,200 100% 1,200 0 0

St. Simons 12,300 10% 1,230 90% 11,070

Jekyll 4,400 20% 880 80% 3,520

Little Cumberland 1,600 100% 1,600 0 0

Cumberland 15,100 10% 11510 90% 139590

TOTAL 76,300 37% 28,090 63% 48,210

Total acreage estimates are from Johnson, A. S. et al. (1971).
Acreage distributed to Holocene and Pleistocene -Eir-e-approxi-
mated from map (Figure 1) of the coastal islands in Hoyt,
J. H. (1968).

Includes forested area, pastures, beaches, and dunes, and
freshwater marshes and ponds. Does not include salt marsh.

barrier islands which consist entirely of Holocene deposits.

There are six islands in this category: Little Cumberland

Island, Sea Island, Little St. Simons Island, Blackbeard

Island, Wassaw Island, and Tybee Island. There are numerous

other, minor islands in addition to the ones listed here.

c) "Holocene deposits" refers to the geologic origin of

the subsoil and represents a condition which is found on all

twelve islands. Likewise, "Pleistocene deposits" is a

geologic term referring to the origin of specific subsoil

deposits on a portion of the six Pleistocene islands.

d) As a general rule, large islands support more species

of plants and animals than small islands (MacArthur and

Wilson, 1967). The Georgia Pleistocene islands represent

larger land masses, averaging four times the land mass of

Holocene islands. However, Blackbeard Island (3900 acres),

the largest of the Holocene islands, is almost as large as

Jekyll Island (4400 acres), the smallest of the Pleistocene

islands. In addition, the Pleistocene islands exhibit the

added diversity of both Pleistocene and Holocene terrain,

providing another reason for a greater floral and faunal

diversity on the larger Georgia islands.

e) Isolation is another important phenomenon which

affects island ecology (MacArthur and Wilson, 1967). The

Georgia barrier islands are isolated from the mainland and

from each other by varying distances of salt marsh, tidal

creeks, and estuaries. Obviously, these islands are not

equally isolated, but there has been no attempt to measure

the varying degrees of isolation. How the isolation factor

affects coastal island ecology will vary from island to

island and depends on the mobility of the species of plant

or animal in question.

Two points must be kept in mind. First, the thesis of

isolation and island ecology (MacArthur and Wilson, 1967) has

been developed primarily for isolated oceanic islands and not

continental islands such as the Georgia islands which are in

close proximity to populations on the mainland. Secondly, the

Georgia Pleistocene islands were connected to the mainland prior

to their insularization by a rising sea level (Hoyt, 1967, 1968).

Thus, a full complement of mainland flora and fauna was probably

originally present, while any species absent today may represent

extinctions due to man or the restructuring of the habitat and

not to the inability of mainland species to cross salt water

barriers.

2. Hydrologic Factors

Artesian water below the coastal island provides the

primary source of water for human consumption (McCallie, 1908).

Wise management of the principal artesian aquifer is essential

to the futureofman on the coastal islands. Except for arti-

ficial irrigation, however, this source of water is inaccessible

to island plants and animals. The natural island ecosystem

depends on a shallow, island water table.

The island water table C.Figure 3-2) has been described as

Figure 3-2
Zin

rans ration

MKT

9W
Ground Water
'00000/ Seqmge

salt Fresh 0-0 Oe
Water Water .000,
Intrusion Lens
Ft

L 000
Source: Brown, J.S., 1925,44A StudY of Coastal Ground Vfter," USCIR Water Sup* e@. 537
p__

a lens of fresh water floating on salt water within the porous

material of the island subsurface (Brown, 1925; Crandell, 1962).

The concept of a fresh water lens is particularly applicable to

small, sandy coastal islands (Brown, 1925). Because the specific

gravity of fresh water (sp. = 1.00) is less than that of salt

water (sp. = 1.025), the fresh water lens behaves like an

iceburg, floating some forty feet below sea level for every

foot above sea level.

Rain is the only source forrecharging island ground water.

As rain collects on the island, its weight induces a flow of

water down and laterally, ultimately discharging below sea

level along the margins of the island. This one-way flow of

water prevents salt water from intruding into surface layers

where high chlorinity would kill the dense mat of roots.

The existence of a fresh water lens has been assumed for

a permeable barrier island sou--h of Long Island, New York (Art,

1973) and will be assumed in some form for Georgia coastal

islands. The existence of such a fresh water lens requires

uninterrupted permeability of ground water to a depth 40 times

its height above sea level as well as contact along its lower

surface with intruding salt water. The presence of impermeable

barriers such as limestone strata reduce the size of the

reservoir but do not change the concept of a large, underground

reservoir which ameliorates fluctuations in the ground water

level, prevents salt water intrusion, and induces a lateral

flow of fresh water to the ocean.

The level of the water table above sea level is lowered

as ground water is removed from the system by lateral flow,

evaporation, and transpiration (Figure 3-2). The water table

rises when rain recharges the supply of ground water. The ratio

of surface (size of island) to volume (quantity of water in the

lens) explains why a given amount of rain induces a magnitude

of change in the water table which is inversely proportional to

the size of the island. In other words, water levels on small

Holocene islands will be more critically affected by rainfall

than on larger islands of primarily Pleistocene origin.

3. Wind and Salt

Scientists have debated the relative effects of wind and

salt on dune communities for years. Several papers (Art, 1973;

Boyce, 1954; Martin, 1959) go a long way in resolving differences

and establishing facts.

a) Tiny droplets of salt water are ejected into the

air from breaking waves. Wind speeds generally in excess

of ten miles per hour carry great quantities of these

droplets onto the islands. Most of the airborne salt is

deposited within 350 meters of the surf line (Martin, 1959).

At 1000 meters, airborne salt is approximately one percent

of the concentration measured at the surf line.

b) Airborne salt deposited on leaf and twig surfaces

is injurious to plants, depending on the concentration of

salt and the susceptibility of the species involved (Boyce,

1954). Tolerant species are selected in the exposed fore-

dunes. Exposed twigs and leaves of less resistant species

are killed, causing a natural pruning effect which results

in the characteristic shape of the island canopy facing the

ocean. Fine structures (grass blades, pine needles)

collect greater salt concentrations than broad surfaces

(oak leaves). Given equal tolerances, pines will be killed

before oak trees.

c) A number of mineral nutrients essential to plant

growth are made available to the island community only in

the form of airborne salts deposited on foliage (Art, 1973).

Thus, airborne salts must be considered as an essential

nutrient source as well as an injurious defoliant.

d) Eventually, there is formed over the leading edge

of the coastal islands a characteristic forest canopy which

is smooth, dense, and shaped like an airfoil (Figure 3-3).

Concentrations of airborne salts beneath the canopy are

very low relative to the air stream above (Boyce, 1954).

Disruption of the canopy, natural or otherwise, exposes
trees which are not acclimated to high salt concentrations

and wind buffeting. Severe trauma and injury to foliage

is the common result.

e) Relative to big islands, a greater percentage of

vegetation on small islands is affected by airborne salt,

based on the estimate that salt droplets rarely travel

farther than 1000 meters from the surf line. Smaller

Holocene islands represent a more rigorous salt-affected

Figure 3-3

Hypothetical
Cross-Section
of a
-50 Georgia
Coastal
-40 Island

-30

-20

-10

MAX
Secondary Plirnary -7777-1
Dune Dune
Slough Ridge Ridge
SeStable or
Tidal Upa River rn,_Sta,**
Creek Serni-st`= I 8=h
Forest _J

dimensions and features vary from island to island.

A semi-stable dune or dune ridge is constant in terms of position
on the shoreline, but functions as part of the sand-sharing system.

A stable dune or dune ridge is a dune which has reached its peak
elevation and is covered with woodland vegetation.

Source: Clement, C. D., 1971, "Recreation on the Georgia Coast: An
Ecological Approach", Georgia Business: Vol. 30, no. 11, p. 1-24.
Adapted by Mr. J. R. Richardson

environment relative to larger, primarily Pleistocene

islands and the distant mainland.

f) Salts do not accumulate to toxic levels in exposed

soils because periodic rain leaches the salts from the

upper levels of sand (Boyce, 1954). Salts generally affect

plants by direct contact with leaf and stem surfaces.

g) Airborne salt is directly related to the proximity

and intensity of surf. Dramatic changes in dune plant

communities should be anticipated as fluctuations in

shoreline and offshore sand bars affect local surf patterns.

h) Nitrogen in a form available to plants is missing

from airborne salt and appears to be a limiting nutrient

in the dune community. Artificial application of nitrogen

will induce a significant increase in plant growth. How-

ever, thereis a corresponding decrease in resistance to

salt toxicity by those plants treated with nitrates.

Application of nitrate to stimulate dune vegetation could

result in increased salt sensitivity and loss of certain

species which normally survive in exposed areas.

In general, any fertilization of the dunes can he

expected to change the associated plant community. Natural

vegetation may be replaced by a typical species, such as

the invasion of camphorweed on the North Carolina Outer

Banks following fertilization experiments (Graetz, 1973).

The loss of beach by the overstabilization of beach grass

(Ammophila breviligulata) dunes within Hatteras National

Seashore is a well known case of management repercussions.

Based on the above experience, fertilization of dunes in

Georgia should be handled with great caution.

4. Fire and Lightning

Fire is a physical factor which is primarily responsible

for perpetuating the Vine-grassland community of the coastal

plain. The role of fire on coastal islands is less clear,

though there is abundant evidence for the regular occurrence

of fire on these islands in the past. Most island burns seem

to be restricted in area because of sloughs and slow burning

live oak stands.

The ecological effect of a fire depends on how it burns

(crown vs. ground fire) and how hot it gets. Heat depends on

the quantity and quality of fuel (litter, dried grasses, oak

leaves), the amount of wind, and the amount of moisture.

Infrequent fires tend to be hotter fires since there is ample

time between'burns for fuel to accumulate. Since natural fires

are usually ignited by lightning and since the number of times

an island is struck by lightning should be directly related to

the size of the island, it could be assumed that the smaller

Holocene islands are burned less frequently but more severely

than the larger Pleistocene islands.

Ground fires that are fueled by grasses are injurious to

broad-leafed shrubs and trees and select for pines. Fires

fueled only by leaf litter tend to be creeping fires, producing

insufficient heat to kill larger hardwoods. Palmetto (Serenoa

repens@ if infrequently burnedproduces a very hot fire.

Holocene islands tend to support understories predominated by

grasses, shrubs, and palmetto; infrequent burns will be severe.

Pleistocene islands frequently support mature forests of live

oak with very little understory. Fires in these ai@eas will be

mild, perhaps even contributing to the maintenance of live oak

dominance (Laessle and Monk, 1961). If a Pleistocene live oak

forest is cleared and replaced with a pine-grassland community,

regular ground fires will be sufficiently hot to perpetuate the

latter community (Johnson,et al.,1971).

When a ground fire burns grass and litter, it affects soil

nutrients in a number of ways (Lewis, 19710. As much as 60% of

the total nitrogen in forest litter is volatilized and lost to

the atmosphere. That which is left in the ashes, however, is

more readily converted to nitrate by soil bacteria. The assets

of soil nitrate enrichment must be balanced against the

liability of total organic nitrogen depletion.
The solubility of important cationic nutrients (Ca++
Mg++, K+) is increased many times. Pleistocene soils with a

significant humic content in the upper layers could be enriched

by this conversion, but Holocene soils may be depleted by the

rapid leaching of surface nutrients. Thus, frequent ground

fires burning over Pleistocene soils may serve to release

nutrients and stimulate productivity, while infrequent ground

fires over inadequate soils (Holocene conditions) could deplete

soil nutrients and injure a larger percentage of forest trees.

The value of,fire in selecting particular forest associations-on

coastal islands is a subjective, poorly understood topic which

requires more study. The role of fires, soils, and island

nutrient budgets should also receive further study.

Lightning, in addition to starting fires, is an important

killer of southern pines (Pinus palustris, P. elliotti, P. taeda)

(Baker, 1973). A pine which is struck by lightning usually dies,

although lightning is generally the indirect cause (Komarek, 1973).

Most pines are weakened by the strike and succumb to beetle

infestations. Oak, on the other hand, generally survives a

lightning strike.

Under natural conditions, pines tend to be infrequently

scattered throughout the forest community of coastal islands.

Pines also tend to be considerably taller than the associated

hardwoods and are thus more susceptible to lightning strike.

By selectively injuring pines which are not particularly

abundant, lightning may play a significant role in affecting

the distribution of pines on coastal islands.

Values and Vulnerabilities of the Physical Factors
Shaping Coastal Island Ecology

1. A fresh water lens is the best description available

for explaining the dynamic, fluctuating behavior of the

island water table. It seems evident that island commun-

ities have probably developed in response to the magnitude

of fluctuations in the water table. Activities which would

alter natural flow patterns (fill, causeways, drainage

ditches, landscaping, etc.) would be expected to have a

dramatic, perhaps damaging effect on the natural behavior

of -the water table. Excessive removal by pumping of island

ground water (depths less than 60 feet) can result in a

cone of depression and pcssible salt water intrusion.

2. Contamination of shallow ground water supplies is a

potential hazard on coastal islands for several reasons:

- island soils are highly permeable to water, permitting

rapid dispersal of contaminants to surrounding areas

- island soils have low filtering and ion exchange

capacity

- seasonally high water tables would discharge accumu-

lated contaminants into sloughs.

3. Plant communities exposed to ocean wind have probably

adjusted to a nutrient supply from airborne salts. Dis-

ruption of air flow by surfside construction would be ex-

pected to alter (reduce) the nutrient supply to the leeward

of the construction. Conversely, removal of acclimated

vegetation exposes remaining vegetation to lethal doses

of salt, with rapid foliage death.

4. Forests are pruned by wind and salt to form a dense

canopy shaped like an airfoil with leading edge to the

prevailing winds. Clearings in the canopy could expose

forest trees to damaging storm winds, with a resulting

high mortality of trees on the clearing perimeter

(Graetz, 1973).

5. Effects of airborne salt are related to surf activity

and the distance between the surf and the affected plant

species. Construction of piers, groins, seawalls, and

offshore bars will change surf patterns, the salt distri-

bution profile, and probably shift the equilibrium between

plant community and salt distribution.

6. Fire stimulates herbaceous growth and selects-fire-

adapted-species. The effects of fire on coastal islands,

however, may be detrimental since litter is a critical link

in nutrient cycling. Coastal island soils do not have thq

well-developed.B horizon needed for trapping nutrients

released by a fire.

7. On the other hand, historical fires may have been an

important factor in shaping the islafid community. Research

should be carried out to determine the effects of island

fire and its historical role on the Georgia coastal islands.

Soils

A knowle-ge of island soils is important to the under"

standing of island ecology. Soils are involved in water move-

ment and nutrient cycling. The chemical and physical charac-

teristics of soil influence the distribution of flora and

fauna. Island soils are closely associated with the island

water table; identification of soil type can provide informa-

tion on the frequency of flooding and the proximity of the

water table to the surface of the terrain in question. The

following is a brief description of factors influencing soil

information on Georgia coastal islands (Wilkes,et al.,1974;

Byrd,et al.,1959).

1. Soils develop from a parent material which largely

determines the chemical and mineralogical composition of

the soil. Most Georgia island soils have developed from a

.near homogeneous quartz sand deposited during the geologic

formation of the barrier islands. Quartz sand is highly

resistant to weathering, with poor water retention quali-

ties and a low capacity for nutrient storage. At least

one soil type found in depressions of older, Pleistocene

formations contain signil"icant quantities of clay,.imply-

ing an earlier and unique (for coastal island soils)

association with tidal streams or estuaries. In addition,

a soil type found along the marsh-island interface consists

of a sandy-clay which has developed as a result of

occasional tidal inundation over low sandy areas.

2. Climate affects soil in several ways. Mineral

nutrients are released from parent material by weathering,

but this is not an important factor with quartz sand. A

warm climate promotes rapid decomposition of organic
matter, leaving few organics to accumulate in the soil.
Abundant rainfall leaches cations (Mg++, Ca+ ) from surface

layers, replacing them with hydrogen ions which increase

soil acidity. This is particularly true on the slopes of

steep dunes where leaching is greatest.

3. Topography primarily affects the rate of leaching.

Narrow ridge tops and slopes have soils low in organics

while depressions and flat areas are correspondingly higher

in organics. In low, poorly drained areas, consistently

wet soil retards decomposition of plant tissue. Oxygen is

lower in saturated soils than in well drained soils.

4. Plants and animals play an important role in affecting

soil development, particularly within coastal island quartz

sand soils that are particularly inert to physical and

chemical changes. Plants produce organic matter, primarily

as surface litter in forest soils. Litter decomposes to

humus, and humus chemically traps and binds essential

mineral nutrients.

5. Time is an important factor in soil development. Soils

develop when organic (decomposition) and inorganic

(weathering) products leach from an upper A horizon and

collect in a lower B horizon, ultimately developing a

characteristic identity which differs from the parent

material or C horizon beneath. Weathering of quartz sand

is too slow to register differences among the various

island soils, but certain organic compounds highly resis-

tant to further decomposition have accumulated in signifi-

cant amounts in one Pleistocene soil, providing this soil

type with a stable B horizon.

The above information can be summarized by listing charac-

teristics of Georgia coastal island soils and their effects on

coastal ecology. Almost all these characteristics derive from

the fact that most of the coastal, island soils are.nearly pure

quartz sand and this explains why Georgia coastal island soils

are considered as one soil association unit.

Low Water-Retention Capacity: Sandy soils have a reduced

ability to hold water by capillary action. Thus, well drained

soils loose soil moisture quickly and are characterized as

droughty. Plants associated with such soils must be drought-

resistant species.

Rapid Permeability: Water passes through sandy soils with

little resistance. Impounded water, where it exists, is usually

not trapped by impermeable soils but represents the current

level of the island water table. Droughty ridges adjoin satu-

rated depressions. For this reason, soil associations on

coastal islands consist of soils which differ from each other

primarily by the amount of drainage which, in turn, is directly

related to elevation, the frequency of flooding, and the prox-

imity of the island water level.

Poor Ion Exchange Capacity: There are very few sites on

sand grains where essential mineral nutrients (for example,

cations of K, Na, Ca, and Mg) can be absorbed (chemically

trapped and bound) for subsequent uptake by root systems. Humic

materialsprovide additional sites for nutrient absorption but

these materials generally exis7 only in a shallow, upper A

horizon.

Vulnerability To Leaching: Nutrients released by surface

litter decomposition and not quickly reabsorbed-by soil fungi

and higher plants are apt to be leached to subsurface layers

probably corresponding to the island water table level. A

portion of these nutrients is probably recycled to the surface

by the action of deep tap roots or periodically high island

water levels, but data to this effect are not available.

Absence of the B Horizon: Most coastal island soils are

characterized by the complete absence of a B horizon. The B

horizon represents a zone of accumulation where the mineralized

products of weathering and decomposition are trapped. The

absence of a B horizon means that soil nutrients leached from

surface litter are not routinely trapped in a zone available

to root systems but pass with excess water to ground water

reserves and possibly lost to the community. The absence of

a B horizon also means that island soils do not have a nutrient

reserve bound in clay or loam. Sandy soils are vulnerable to

rapid nutrient depletion if a continuous nutrient input.from

decomposing litter is interrupted.

Low pH: Most coastal island soils are characterized by

acidic conditions which develop for a number of reasons

(Buckman and Brady, 1968).

a) abundant precipitation: rain leaches appreciable
amounts of' exchangeable bases (Mg++, Ca++) from the

surface layers of well drained soils, replacing the

absence with hydrogen ions;

b) the presence of organic complexes (humus): hydrogen

absorbed on the humus dissociates into the soil solu-

tion with comparative ease (older, more level. soils);
c) the production of inorganic acids (H2 S04 and HN03 ) as

a biproduct of organic decay (low, poorly drained soils).

A low pH is indicative of the following conditions (Buckman

and Brady, 1968):

a) a loss of exchangeable bases (Ca.++, Mg++) from well-

drained soils;

b) increased solubility of trace elements (Al, Fe, Mn) to

levels perhaps toxic to certain plant species;

c) a loss of available phosphate (a low pH causes phos-

phate to complex as insoluble compounds);

d) a reduction in the activity of bacteria and actino-

mycetes, reducing, for instance, the rate of bacterial

nitrogen fixation. Fungi are seemingly not affected

by low pH and continue to function in decay, aminiza-

tion and ammonification reactions, all important steps

in the nitrogen cycle;

e) a reduction in total soil nitrogen, probably correlated

to reduced nitrogen fixation.

Conditions which seem unfavorable at first glance (low pH,

reduced microbial activity, etc.) may be necessary under condi-

tions of island quartz sand soil. For instance, it has been

shown that humic material provides most of the ion exchange

capacity in pure quartz soils and that humus is vulnerable to

leaching when reduced to molecular levels. As a conjecture,

reduced microbial activity in the upper soil horizons may slow

the mineralization of humus, thereby increasing the retention

time of humus in the upper horizon and the opportunity (time)

for plants to recycle complexed nutrients (exchangeable bases)

before nutrient-humus complexes are lost to deep layers by

leaching. A higher pH could mean a net loss of nutrients to

the plant community if microbial activity is increased.

Buffering Capacity: Soil flora and fauna are sensitive

to changes in pH. The ability of a soil to resist such changes

is called the buffering capacity. Buffering is enhanced by high

ionic exchange capacity and high concentrations of weak acids

(carbonic, humic), two conditions which are characteristically

absent from well drained island soils. Well-drained, acid

soils are vulnerable to pH changes. If a markedly acid sandy

soil is suddenly brought to a neutral or alkaline condition by

an over-application-o-flime or oyster shells, trace elements can

go completely out of solution, causing plants to suffer from,

for instance, a lack of available manganese and iron (Buckman

-i r%rn\
.and Brady, _LUOO.J.

Pleistocene vs. Holocene: According to the available soil

surveys (Byrd,et al., 1959; Wilkes, et al., 1974), Holocene island

soils are all without a B horizon and exhibit the least quanti-

ties of accumulated organics and horizon development. Pleisto-

cene island soils, as a group, exhibit greater variety and

development (horizon development, organic accumulation, presence

of clay and loam) than Holocene island soils but less development

and variety than mainland Pleistocene soils, Differences in

soils provide another reason why environmental conditions

become more strenuous as one moves from mainland to island and

from Pleistocene island deposits to Holocene island deposits.

Values and Vulnerabilities of Island Soils

1. Litter plays a major role in island soils and must

be protected. Litter reduces leaching in the upper soil

layers by dissipating the force Df.rain as well as pro-

viding most of the ion exchange capacity.

2. Coastal island soil types are closely related to the

proximity of the island water table. Changes to the

water table (drainage, impoundment, etc.) will affect the

type and behavior of the associated soils. Drying soils

decrease in pH (Buckman and Brady, 1968).

3. Coastal island soils are characteristically low in

nutrients, low in ion exchange capacity, high in per-

meability, low in buffering capacity, and low in pH.

These characteristics make island soils sensitive to a

wide variety of manipulative practices such as sewage

disposal, agricultural practices, and landscaping.

4. Soils within a single soil association can be very

different ecologically. For instance, the Kershaw-Osier-

Coastal Beach Association represents soils which have

developed on Holocene island deposits (Wilkeset al. 1974).

The Kershaw series is excessively drained and droughtly.

The Osier series is poorly drained and usually flooded.

These two series represent dramatically different selective

forces on the island community, yet they are closely inter-

mingled in the dissected terrain of Holocene deposits.

As indicators of ecological conditions, soil maps must

employ a scale sufficient to represent soil series.

Nutrient Cycles

Nutrients are chemical elements essential to life. Nutrients

tend to circulate through the environment along characteristic

pathways known as nutrient cycles (Odum, 19.71). The stability

of a biological system depends in large part on the ability

of the system to balance its nutrient budget, to utilize its

resources (turnover) and to compensate for losses with equiva-

lent gains. Coastal islands exhibit characteristic strategies

which acheive a balanced nutrient budget.

Nutrients are classified as inorganic (nitrates, phosphates)
Co 25 mineral ions, etc) or organic (Vitamin B12)- Organic
nutrient cycles are important but will not be discussed for

lack of data. Inorganic nutrients may be classified according

to their primary abiotic source. Thus, gaseous nutrients are

available in the atmosphere and include the elements of carbon,

nitrogen, oxygen, and sulphur. They enter the system as metero-

logical input (dissolved in rain or mixed with atmospheric gases)

and are captured by the stream through such processes as photo-

synthesis and nitrogen fixation. Sedimentary nutrients include

such important elements as calcium, potassium, magnesium, and

phosphorus. These are trapped in the earth's crust and are
released to the system in ionic form,(Ca ++ , Na+, P04__` etc.)

by the weathering and ultimate solution of soil rocks and

minerals.

Gaseous nutrients are available to islands and adjacent

mainland in equal quantities. Mechanisms for photosynthesis

and respiration do not differ significantly between islands and

mainland. Nitrogen is frequently a limiting nutrient, and its

capture by a host of nitrogen-fixing micro-organisms is an

important aspect of community productivity. Unfortunately,

there is little information on nitrogen cycles pertaining speci-

'fically to coastal islands. The fact that excess nitrogen can

stimulate growth of dune vegetation while simultaneously lowering

resistance to salt toxicity (Boyce, 1954) implies a very

delicate role played by nitrogen in coastal ecosystems.

The primary source of sedimentary nutrients is the wea-

thering of rocks and minerals, yet the inorganic fraction of

barrier island soils is almost entirely quartz sand which is

highly resistant to weathering. Barrier islands evidently

maintain levels of productivity equivalent to mainland forests

by substituting the meterological input of airborne salts as

a source of sedimentary nutrinets (Art,et al., 1973).

Figure 3-4 illustrates a hypothetical scheme for sedimen-

tary nutrient cycling based on values for a Long Island, New

York coastal barrier island (.Art,et al., 1973). This scheme is

probably most pertinent to Georgia Holocene islands with poor

soil profiles. A number of observations can be made:

1. Most of the community nutrient reservoir (exchangeable

nutrients) is contained in living biomass (leaves, twigs,

roots, and stems). The remainder is absorbed to soil

Figure 3-4

Hypothetical Cycling
of Sedimentary Nutrients
on Coastal Islands

Figure 3-4 represents a hypothetical method of sedimentary nutrient flow on
a sandy barrier island. Arrow width represents the proportion of flow
relative to other sections of the model. Solid lines represent measurements
from a Long Island, New York barrier island (Art, et al.,1973); dotted lines
represent hypothetical flows which have not been measured. Until we have
actual measurements for a Georgia coastal island, this model cannot be
detailed.

organic matter. There are virtually no nutrients

attached to the mineral elements of the soil.

2. The major nutrient flow is a tight cycle from leaf

production to soil litter and back to leaf production.

The magnitude of this flow has been estimated to be

four to six times the meterological input (Art, et al.,

1973). The percentage of nutrients passing through a

grazing food chain (deer, herbivores, insects, etc.) is

much less.

3. Litter nutrients not immediately reabsbrbed by roots

are leached from upper layers of soil and probably lost

to the community. The relative proportion lost to

ground water and surface runoff, is not known. A

certain amount of recycling of deep soil nutrients

probably occurs, perhaps by deep tap roots or the pump-

ing action of a fluctuating water level.

4. Art,et al., (1974) believe salt droplets deposited on

foliage are the primary source of sedimentary nutrients

into their Long Island coastal forest. They did not

consider the transport of nutrients into the system

by animals to be very important. Such a consumer

transport system is probably more important on Georgia

islands, but a quantitative study has never been done.

Raccoons, deer, and a variety of wading birds repre-

sent significant populations of animals which feed in

the surrounding marshes and deposit their fecal matter

on the island. A study of energy and nutrient transfer

across this marine-terrestrial interface of coastal

islands would add significantly to the understanding of

coastal island ecology.

There are a number of interesting similarities in nutrient

cycling between Holocene formations and moist tropical forests

(Art,et al., 1973). Both systems have highly weathered soils

which produce very small quantities of sedimentary nutrients.

Most of the exchangeable nutrients are bound*within living

biomass and not the soil. Thus, both systems must quickly

recycle nutrients from leaf litter back to living biomass or

lose those nutrients to rapid leaching. Because of this simi-

larity, some of the following characteristics of moist tropical

forests might be pertinent to Georgia barrier islands.

1. Tropical forests exhibit nutrient conservation

mechanisms (Odum, 1971) such as a close approximation of

fungal mycorrhyza and tree roots permitting a direct

transfer of nutrients from litter to living biomass.

Similar mechanisms may exist in the coastal island litter

layer.

2. If tropical forest is cleared, the soils rarely support

more than a single crop before productivity begins to decline.

Soil nutrients are quickly exhausted or leached away. Holocene

island soils would be expected to behave similarly. It would

be interesting to know how early plantations maintained soil

productivity, even on Pleistocene soils with the beginnings

of a B horizon.

3. The narrow litter layer is a critical zone of nutrient

transfer; its removal short-circuits the nutrient cycle.

Fire on coastal islands removes the litter layer and

increases the solubility of soil nutrients. Fire would

be expected to have its most disruptive effect on nutrient

cycles in Holocene areas. It has been shown (Remezov and

Pogrebnyak, 1969) for dry, sand soils under pine that the
litter contains 20-50% of the total amounts of Ca++, Mg++, P+.
and K+ involved in the soil's yearly cycle. They demon-

strated under these conditions that even one removal of

forest litter could impoverish the soil and reduce soil

nutrients. The effect may be quite perceptible even

several decades later.

Values and Vulnerabilities of Nutrient Cycling

1. With a general lack of a B horizon in coastal island

soils, the exchangeable nutrients from decomposition pro-

ducts probably pass from litter and humus directly to the

roots of the associated plant community, effectively elimi-

nating the need for a well developed subsoil layer of B

horizon. Removing litter could break the nutrient cycle

and disrupt community productivity.

2. The artificial application of fertilizers to coastal

island soils will probably alter the structure of natural

plant communities which have adpated to prevailing winds,

salt spray, and nutrient-poor, acidic soils.

Coastal Island Fauna

A considerable amount of faunal life history and distribu-
67

tional data has been collected for the Georgia coastal islands

(Hillestad, 1975; Johnson,et al.., 1971; Johnson, et al.,appelidix,

1971). It is evident from this work that the ecology of animal

populations on coastal islands is different from what is encoun-

tered on the adjacent mainland primarily because of one essential

fact: coastal islands are islands and not peninsular extensions

of the mainland. This fact manifests itself in a number of ways.

1. When conditions are unfavorable, mainland fauna has the

opportunity to move to more favorable areas. When condi-

tions return to normal, a species can return to previously

vacated areas. The opportunity for migration on coastal

islands is reduced, depending on the mobility of the species.

Rattlesnakes and raccoons are excellent swimmers and are

widely distributed among the islands. The discontinuous

distribution of squirrels, mice, and opossums may indicate

periodic extinction in localized areas as well as infre-

quent recolonization. The distribution of species intoler-

ant to salt water (salamanders) will be discontinuous and

localized on a few older Pleistocene areas.

2. The capacity of an island to support species is related

to its size (MacArthur and Wilson, 1967). Thus, within

a particular geological category, fauna of larger islands

should be more diverse than smaller islands. For example,

the diversity of Wassaw (2500 acres) fauna should be

greater than Little Cumberland (1600 acres) fauna.

3. Insularity isolates some breeding populations and

9-%4!b
VO

permits the development of new forms (genetic drift). The

indiscriminate introduction of mainland genotypes can

obliterate, through interbreeding, unique island forms

which may have taken thousands of years to develop. Four

taxonomically distinct mammals are currently recognized

for the Georgia barrier islands (Johnsongt al, 1971),

including the Cumberland Island pocket gopher (Geomys

cumberlandius), the Anastasia Island cotton mouse

(Peromyscu gossypinus anastasae), the St. Simons Island

raccoon (Procyon lotor litoreas), and the Blackbeard Island

deer (Odocoileus virginianus nigribarbis). Johnson,et al.,

(1971) discuss management options for protecting these

unique species.

4.. Island communities with a reduced number of species

develop sensitive equilbria among the existing species.

The introduction of new, seemingly innocuous mainland

species to island faunas has the potential of setting off

significant perturbations within the island community.

Introductions are frequently upsetting to communities and

should be practived with caution.

5. Native island species (endemics) are less adaptable

than mainland species and more prone to extinction when

new species (exotics) are added to the community (Carl-

quist, 1974). Adaptation to island life seems to reduce

genetic fitness and with it the ability to compete. The

more endemic the organism, the more prone it is to

extinction.

Virtually all populations oscillate in density. However,

the more highly organized and mature the community and -the more

stable the environment, the lower will be the fluctuations in

population density with time (Odum, 1971). It has been shown

that organization, maturity, and stability decrease as one moves

from mainland to island and from Pleistocene island to Holocene

island. It should not be surprising, therefore, that dramatic

oscillations in the density of animal populations on unmanaged

Holocene islands is a characteristic feature of coastal Georgia

ecology. Over periods of a few years, densities of mice, deer,

and raccoon can reach levels substantially higher than adjacent

mainland populations, only to crash in massive dieoffs (personal

observation of the authors). Levels higher than normal can

probably be associated with periods of abundant food, the

inability of excess animals to relieve population pressures by

emigrating out of the high-density areas, and the noticeable

lack of predators (bobcats, humans, bear, lion) available to

harvest the excess animals. Although little data is available,

the "boom and bust" characteristic of island populations can

probably be extended to insect populations as well, including

species of noxious insects (Johnson,et al.,1971) which can

have such an impact on recreation and development.

Populations without regulatory mechanisms tend to overshoot

their food source and crash. While the sudden unavailability

of food is a likely candidate for initiating a crash, other

causes do exist. For instance, populations develop increased

susceptibility to disease at high densities. Raccoon popula-

tion density may be regulated by disease (Johnson, 1970). A

crash by one species is frequently associated by crashes in

other species, implying an underlying cause such as island

mast production (acorn crop).

It is not necessarily w-ong to adopt a laissez-faire

attitude toward the regulationofconspicuous island mammals,

particularly on islands which are being preserved as natural

environments. Coastal island animal populations have undoubtedly

undergone periodic, severe oscillations for as long as the

islands have been in existence. If so, island communities have

almost certainly developed characteristic and unique responses

to the oscillations. Several islands are classified as

natural but are, in reality, quite mission-oriented (Sapelo,

Blackbeard) , with management plans which damp natural oscilla-

tions while selecting for desireable game species. In a state-

wide multiple-use program, management of this kind has a worthy

cause but should not preclude the existence of other represen-

tative islands left to natural conditions.

Values and Vulnerability of Coastal Island Fauna

1. Georgia coastal islands support unique faunal types.

Protection of habitat and continued isolation of the

species are the es-s-ential ingredients of management.

2. Island populations should be expected to fluctuate in

numbers more than mainland populations. Controlling

normal population oscillations may alter coastal ecology

patterns. Undamped oscillations may, however, result: in

outbreaks of disease and massive dieoffs. A population

response such as this would.be undesirable within areas

with a high density of people.

3. Mobility is a key to survival when food resources run

low. Barriers (fences, roads, developments) impede move-

ment patterns and would increase stress on island popula-

tions.

4. When populations are high, food availability will be

critical. At such a time, browsing species (deer) may

come into conflict with many as they search for alternate

food sources such as gardens and landscape plantings.

5. Coastal islands are living laboratories for the study

of insularity and its effects on coastal animal populations.

Aquatic Systems

Most references to coastal aquatic systems deal with the

extensive Spartina marshes, creeks, and estuaries which separate

island from island and island from mainland. There is an addi-

tional category of aquatic systems, collectively called island

sloughs, which play an important modifying role in terrestrial

island ecology. Sloughs are critical as a source of water for

island wildlife. As nutrient traps, sloughs represent a step

in almost all island food chains. As habitat, sloughs add

diversity to islands, support territory for rookeries, and

provide resting and feeding areas for a wide variety of

resident and transient species.

Because of sedimentation and the accumulation of organic

matter, aquatic systems tend 7o pass through a series of success-

ional stages toward a climax forest condition. A more or less

regular but acute physical diSruption imposed from outside the

system can maintain the system at some intermediate point in the

development sequence (Odum, 1971). The principal disruption

on coastal islands is a fluctuating water level, although

saltwater intrusion and fire represent additional d-isruptions.

Thus, we can consider island sloughs as pulse-stabilized,

fluctuating water level ecosystems which respond to outside

forces.

1. The Hydrologic Cycle as a Force

The level of the island water table (Figure 3-2)represents

the level of exposed water in island sloughs. When it rains,

sloughs experience a rapid increase in the water level. This

rate of increase provides an --Important signal for initiating

breeding behavior in slough-dependent animals like frogs and

toads. There is also a steady loss of water via ground water

flow, runoff, and evapotransp---ration which results in a gradual

decrease in water level. During periods of extended dry weather,

a slowly dropping water level stimulates a continual series of

successional changes within the slough community. Rapid

increases in the water level _-1-nitiate sudden dieoffs in emer-

gent vegetation, in effect resetting the environmental clock

to an earlier, open-water successional stage. Gradual increase

and rapid decrease in water levels represent abnormal system

-responses which probably would disrupt normal behavior patterns.

A fluctuating water level acts as a nutrient pump. When

the water level drops, nutrients in bottom muck become available

to emergent plants and are transferred to plant biomass. At a

very low water level, the slough bottom will dry out, stimulating

aerobic-decomposition of accumulated organic matter which pre-

pares the system for rapid nutrient release. A sudden rise in

water level distributes mobilized nutrients throughout the

flooded system. Emergent plants are drowned (harvested),

rel-easing additional nutrients. Production is shifted to

submergent and floating vegetation as the system returns to an

earlier successional stage.

How a community responds to a fluctuating water level

system depends on the frequency and amplitude of th6 fluctua-

tion. Fluctuations in ground water probably increase in ampli-

tude from mainland to island and from Pleistocene island to

Holocene island. Mainland communities have alternate sources

of water (rivers and streams) and a water table more resistant

to change. The breeding of aquatic species on the mainland does

not have to be closely linked with the dynamics of a fluctuating

water system. On a Holocene island-, however, acceptable condi-

tions for breeding within aquatic systems are highly unpredic-

table and usually of very short duration. Holocene island

communities tend, therefore, to be more responsive than main-

land communities to variations in water level.

2. Salinity as a Force

Certain island sloughs are periodically flooded by

extreme tides, introducing salinity as an alternate perturbing

force. Heavy rains dilute salinities, establishing conditions

for salt-sensitive plants suc-a as cat-tail (Typha). Tidal

inundations raise salinities, killing salt-sensiti-Ve plants

while favoring salt-resistant plants. Salinity fluxes interrupt

succession, stimulate nutrient turnover, and maintain open-water

systems.

Tidal inundations also permit access to island sloughs by

several salt marsh species of fish (mollies)(Poecilia latipinna),

killifish (Fundulus species), and top minnows (Cyprinodon

variegatus) which normally ma--'ntain subsistence levels in

neighboring tidal creeks. Within the sloughs, populations grow

to enormous numbers in the absence of marine predators, feeding

on a near limitless supply of rich organic detritus on the

slough bottom. Densities in excess of a thousand fish per

square meter can be realized. Salinity-pulsed sloughs are

particularly important feeding areas for such animals as

herons, egrets, grebes, anhingas, and turtles.

Salinities vary widely (0% - 30%) between sloughs and

temporally within sloughs depending on the frequency of tidal

inundation, rainfall, and evaporation. Temperatures fluctuate

widely since water is shallow and exposed to sunlight without

the regulatory effect of emergent vegetation. Since saline-

pulsed sloughs tend to be rich in rotting organics, dissolved

oxygen frequently drops to zero. Fish inhabiting these sloughs

can tolerate a broad range of temperatures and salinities

(Bacon,et al.,,1967; Garside and Jordan, 1968) and even have the

ability to gulp air at the surface when dissolved oxygen drops

to zero (Odum and Caldwell, 1955).

3. Fire as a Force

Fire reestablishes open water in aquatic systems (Cypert,

1961; Ward, 1942). When conditions are particularly dry,

bottom peat can dry out and. burn, effectively lowering the

bottom of the slough. Such a dramatic disturbance may occur

only once in a hundred years and still be an important factor

in the pulse stability of an aquatic system. Due to the infre-

quent nature of this force, its historical role as a disruptive

factor on coastal islands is difficult to document, but the

potential effects are very real and should always be considered

when dealing with coastal island sloughs.

There seems to be a limitless variety of sloughs on the

coastal islands, but virtually all are pulse-stabilized. Slough

variety is the result of a gradient effect in the intensity of

the forces acting upon the sloughs. Water level fluctuations

are greater on Holocene formations than on Pleistocene formations.

Within a Holocene island, fluctuations will be greater on the

newer portions (behind the primary dunes) than on older portions

(central forested areas). Deep depressions dry out less

frequently than shallow depressions. The impact of salinity

depends on the frequency of inundation and the dilution factor

(amount of sea water reaching a given quantity of fresh water).

The effect of fire depends on the frequency of the burn and the

depth to which the bottom of the slough had dried prior to the

fire. Limiting nutrients, drainage, soil conditions, soil pH,

proximity to airborne salt, and many other factors add to the

variety of island sloughs.

Virtually nothing has been done to categorize coastal

island sloughs. A tentative classification based on a cursory

investigation of Cumberland Island (Pleistocene with Holocene

additions) and Little Cumberland Island (Holocene) is as follows:

1. Holocene Freshwater Slough: long and narrow, forming

between dune ridges; frequently shaded by overhaning

oaks; water levels fluctuate greatly.

a) Deep Sloughs: flooded for most of the year;

usually choked with floating aquatic plants

(Heteranthera, Utricularia, Limnobium); fish

(Gambusia) rarely accumulate to densities that

would provide an important food source for herons

and egrets.

b) Moderate to Shallow Sloughs: alternately flooded

and dry; willows in the low areas, saw grass

(Cladium) at moderate levels, annuals (Pluchea,

Saururus) at shallow levels where flooding is

occasional. Gambusia present but in moderate to

low densities.

c) Primary Dune Depression: very temporary; forming

for short periods of time (several weeks) in the

interdunal depressions following heavy rains; vege-

tation is emergent grasses and shrubs (Myri:!a clumps).

Because numbers of predators are reduced, frogs,

toads and mosquitoes can breed in enormous numbers

in these sloughs.

2. Pleistocene Freshwater Slou@Ths: variable in size;

usually round with gradually sloping edges; forming in

broad depressions.

a) Deep Sloughs: permanently flooded; variable amounts

of open water; vegetation can consist of rooted

emergent perennials (Decodon), floating mats

(Heteranthera, Utricularia, Limnobium), or rooted

submergents (Nelumbo, Hymphaea); low numbers of

prey fish (Gambusia) since these ponds frequently

support major predator fish (bass (Micropterus),

sunfish (Lepomis) ).

b) Moderate Sloughs: usually flooded; surface often

choked with floating mats (Heteranthera, Utrica-

laria, Limnobium); very similar to deep Holocene

sloughs.

c) Shallow Sloughs: occasionally flooded; grasses

(Spartina, Andropogon, Setaria) where bottom dries

out; saw grass (Cladium) and various trees (Acer,

Salix, Nyssa) where bottom soil remains saturated.

Saline-Perturbed Sloughs

a) Sloughs with_Frequent Tidal Inundation: usually

flooded; open water; vegetation consists of sub-

mergents (Ruppia) or surrounding emergent grasses

(Spartina, Distichlis, Juncus); high salinities

(5-20%); capable of supporting enormous numbers of

fish (Gambusia, Fundulus, Cyprinodon,.Poecilia).

b) Sloughs with Infrequent Tidal Inundation

1) Deep Sloughs: flooded for long periods of time;

open water systems rich in organic detritus;

salinities variable but usually low M); a

wide variety of associated plant species with

varying salt tolerances; capable of supporting

enormous numbers of fish (Gambusia, Fundulus,

Cyprinodon, Poecilia); the most productive of

all sloughs as a food source for island wildlife.

2) Shallow Sloughs: flooded briefly; shallow, flat

depression with varying percentages of exposed

clay, grasses (Spartina), or woody shrubs (Iva,

Baccharis); occasionally important for concen-

trating fish while water levels are receding.

4. Fire@-Ferturbed Sloughs: this is a speculative cate-

gory for an observed aquatic system on Cumberland

Island; extensive, deep, open water system with a

variety of emergent grasses; an almost total absence

of woody shrubs and broad-leafed aquatics.

S. Drainage Depressions: Soil usually saturated but

rarely flooded; generally forested areas (Magnolia

virginiana, Hyssa, Acer) with an understory carpet of

mixed grasses, herbs (Saururus), and woody shrubs and

small trees (,Lyonia, Cephalanthus, Myrica, Ilex).

Because of their inherent diversity, island sloughs can support

a wide variety of plant communities. Sloughs represent perhaps

10% of a total island area but account for the greatest part of

the island flora and fauna.

Aquatic systems stimulate faunal diversity in several ways.

1. A variety of plant species and plant communities provide

for a greater variety of faunal niches.

2. A greater faunal diversity is associated with an ecotone

or edge effect. In other words, a wider variety of

species can exist along an interface of two adjoining

plant communities than in either community by itself.

The perimeter of every slough provides additional edge

effect.

3. Coastal islands can be dry islands. Sloughs provide an

essential source of fresh water during periods of

drought for species which would otherwise not survive.

4. Many animals are specialists, requiring a particular

set of conditions (water depth, density of emergent

vegetation, availability of food, etc.) for feeding or

reproducing. With a wide variety of sloughs, adequate

conditions can usually be found at one or another

location on an island at any one time. As conditions

change, these animals move from slough to slough,

staying within optimum conditions.

Coastal island fauna, particularly those species associated

with Holocene formations, have developed so closely with the

instability of the island environment that many species require

fluctuating water levels for survival. These are called

opportunistic species since they coordinate their life cycle

with temporary island conditions whenever tl-..e opportunity

arises. The following are examples of opportunistic species:

1. Treefrogs will go for months without breeding,

scattered throughout the island forest and seemingly

oblivious to occasional thunder showers. When a

torrential rain of significant magnitude occurs, indi-

viduals from all over the island will gather in dense

breeding congregations at a few selected sites on the

island, particularly flooded areas with dense emergent

vegetation. This opportunistic behavior insures certain

critical conditions:

a) sufficient water to maintain flooded pools for the

duration of larval (tadpole) development;

b) habitats low in predators; Grassy sloughs are those

which characteristically dry out, depressing resident

predator populations such as fish and turtles.

c) irregularly pulsed breeding; Predators are fre-

quently slow to react to surges in prey species.

By massing huge numbers of tadpoles at infrequent

localities, a sufficient number of young are sure to

survive.

2. The marsh killifish (Fundulus confluentus) is a brackish

water@species which invades island sloughs with periodic

connections to the marine environment. This opportunis-

tic species will breed during the highest water levels

and deposit eggs at the very margins of the sloughs

(Harrington, 1959). When water levels recede, the eggs

may remain stranded on high ground for months but will

hatch within fifteen minutes upon being reflooded

(Harrington, 1959). The salt marsh mosquito (Aedes

solicitans) also deposits its eggs which hatch upon

being reflooded, so the marsh killifish achieves at least

two results by its unusual opportunistic behavior:

1) protecting its eggs from aquatic predators and 2)

coordinating its young with the available food supply

(mosquito larvae), being at the right time and the right

place when the mosquito eggs hatch.

3. The wood stork (Mycteria americana) is so inefficient

at catching fish that it must specialize on sloughs

where receding water has concentrated fish to a critical

density. The stork nesting cycle in Florida is coordi-

nated with periods of falling water level when fish

supplies will be sufficient for rearing young storks

(Kahl, 1964). Visiting wood storks on the Georgia

coast exhibit similar feeding behavior.

4. The success of a mosquito hatch in an island slough

usually depends on the presence or absence of fish.

Some mosquitoes tend to utilize temporary sloughs

(grassy) which-periodically dry up, eliminating T-esident

fish predators during the dry periods. Several oppor-

tunistic species of fish, however, manage to persist in

such sloughs during dry periods by taking refuge in

alligator burrows (refugia) which extend below water

level. When the rains come, water levels rise, mosquito

eggs hatch, and the fish are there to utilize the food

source for their own breeding cycle.

It is obvious that a drained slough ceases to pump

nutrients and provide the variety of food and habitat associated

with a normal fluctuating slcugh. It is not so obvious that a

slough with a stabilized water level will behave in the same

way. Nutrients will become locked in the bottom, succession

will proceed with vegetative growth choking open water, and

habitat for opportunistic species will be reduced or eliminated.

If a majority of island sloughs were to be stabilized, a major

shift in associated fauna could be ant icipated.

Values and Vulnerability of --sland Sloughs

1. Sloughs are maintaiiied and perpetuated by perturba-

tions in the environmen--, usually a fluctuating water

level but occasionally salt water intrusion or fire.

Stabilizing water levels or blocking natural drainage

0113
U%'@P

channels will result in rapid successional changes within

the slough, possibly leading to the complete loss of the

slough system.

2. Sloughs provide for a major part of the floral and

faunal diversity of coastal islands.

3. Sloughs provide food and water for island animals.

4. Sloughs are superb systems for environmental education.

The Strategy of Survival on Coastal Islands

Ecosystems are more easily disturbed by unfamiliar forces

(man, introduction of exotic animals, etc.) than by familiar

forces (fluctuating water levels, salt, insularity, etc.)

(Odum, 1971). Unnatural oscillations in population densities

can result in the extinction of some island species. Given

sufficient evolutionary time, however, ecosystems adjust to

familiar forces. -Resistent species and adaptive strategies

help to damp oscillations within the system. Although little

supporting data currently exists for coastal islands on the

Georgia coast, the existence of such uniquely specialized

strategies is almost self-evident. If some coastal islands

are to be maintained in a natural condition, manipulations to

the environment must be carefully considered with respect to

their impact on island ecology. A minor manipulation could

theoretically initiate irreversible changes in, for instance,

the species composition of island forests by interrupting

subtle adaptive strategies between interacting species.

Using a hypothetical example, let us assume that Holocene

islands have been severely browsed by periodic highs in deer

density for the last 5000 years. We can ask the question: What

happens if these dominant herbivores are managed at constant,

low levels? This would remove not only the periodic impact of

intense high-density browsing but also the periodic lack of

impact which follows population crashes and reduces browsing
pressures to zero!. A number of -changes could occur:

a) Since different browse plants have different palatability

and browsers tend to be specialists, plant species with high

palatability would continue tc receive heavy browsing pressure,

while less palatable species would now be ignored. There

would be a shift in forest composition to less palatable species.

b) Some island forest species (Persea, Bumelia) currently have

very dispersed distributions. These trees employ a strategy

of producing fruit which is highly attractive to browsers (deer).

Seeds pass through the gut and are dispersed by random fecal

deposits throughout the island. Since the foliage of these two

tree species is browsed by deer, survival of seedlings is

enhanced by rareness. Thus, the occasional seedling germinating

in a thicket will escape notice and survive, particularly if a

major die-off in the deer herd has proceeded germination of the

seedling.

For purposes of the hypot'ietical example, we will regulate

the deer herd at a constantlow density and assume the following

results:

1. Fruit from both forest species is now ignored in

favor or more palatable food;

2. Foliage from the first tree is still preferred, but the

foliage of the second tree is now ignored by the browsers.

The seeds of both species would cease to be widely distributed,

resulting in dense seedling shadows under the parent trees.

Because of its localized abundance, the first species would

become easier to find and receive increased browse pressure,

leading to the loss of all seedlings and the ultimate extinction

of the species from the forest community. The second species

would remain on the island but change its distributional charac-

teristic from dispersed to clumped.

Although the above is a hypothetical example, it could be

tested by monitoring diet selection by coastal island deer at

different population densities and noting the response of

browse plants to varying intensities of selection (palatability).

The purpose of deriving this example is to draw attention

to several ideas:

1. The existence of subtle relationships which might have

evolved within the coastal island ecosystems;

2. The effects such relationships might have on the

structure of an island community;

3. The vulnerability of island communities to seemingly

innocuous manipulations by man.

There must always be a least some examples of totally unmanaged

coastal island systems which can be used for testing and compar-

ing the effects of man-induced disturbances.

Island Communities

A hypothetical cross-section of a Georgia coastal island,
with a number of characteris---ic communities, is shown in Figure

3-3. A relatively level forest of Pleistocene origin is bor-

dered by a stabilized dune ridge of Holocene origin. The figure

represents a prograding shoreline, with primary dunes, fore-

dunes, and berm developing progressively eastward of the

forested secondary dune system.

There are many variations to this cross-section. Holocene

islands exhibit an extended series of forested, secondary dune

ridges. Islands with a retrograding (receding) shoreline have

a reduced or absent primary @.une system. In fact, each coastal

island is different, representing a unique combination of

physical and chemical conditions which impart to it a charac-

teristic behavior and appearance. The complex of beaches, bars,

and dunes can be described as a dynamic system involving the

interplay between sedimentary processes and sedimentary

structures (Oertel, 1974). Nevertheless, island communities,

developing under such variable conditions, display fundamental

similarities common to all of the Georgia islands.

An island community representsa convenient unit of study

because it can be defined as a characteristic assemblage of

plants and animals living together under similar physical

conditions. A community is also a functional unit. Organisms

within a community frequently display common survival strate-

gies, trophic structure, and netabolic patterns (Odum, 1971).

Finally, the behavior of a species within a community is closely

interwoven with that of the other species. Changes in the popu-

lation characteristics of one species can be expected to affect

the other members of the community.

1. Beaches

The ocean beach is alternately called a foreshore Wertel,

1974) by geologists and a coastal beach (Wilkes,et a!-, 1974) by

soil scientists and represents an area which is covered twice

daily by tides. Its physical characteristic is fine sand, high

salinity, and varying quantities of small shell fragments and

sediments.

The ocean beach community is constrained by:

a) the physical pounding of waves and currents on a

a shifting substrate (high water);and

b) periodic exposure to dessication (low water).

Most resident members of the community are burrowing animals

which move with the sand, extending or retracting their

burrows as the shifting sand dictates (Clement and Richardson,

1971). A number of predators (birds and ghost crabs (Ocypode)

during low water, and fish and rays during high water) visit

the beach to feed when conditions are acceptable.

The composition of species within the beach community

depends in large part on the amount of silt and clay which is

mixed with the sand. The ocean beach fully exposed to surf

is a high-energy beach. This type of beach will have a low

silt content and support primarily filter-feeding organisms

00
00

(Odum, 1971). Beaches on the west side of the islands and

beaches protected by sand bars are low-energy beaches which

receive varying degrees of protection from turbulence. Low-

energy beaches, relative to high-energy beaches, contain more

silt and clay, more organic nutrients, and a greater proportion

of deposit-feeding organisms.

Producers (plants) perform a minor role within the beach

community. Diatom colonies appear as brown patches on the

surface of low-energy beaches. These single-called algal plants

are important producers within the estuarine system (Pomeroy,

1959), but total numbers occurringon beaches are probably small

relative to the entire estuary. Other species of algae and some

cord grass (Spartina alterniflora) may be found in small,

scattered patr@hes where turbulence is low.

Consumers, on the other hE-@d, are numerous within the

beach community anu probably play an important role in coastal

ecology. Invertebra-,@s, particularly isopod crustaceans,

polychaete worms, and the coquina clam (Donax), provide an

abundant source of food for shcrebirds. The ubiquitous ghost

shrimp (Callianassa major) is a burrowing filter-feeder occurring

most abundantly on the high-energy beaches. Fecal pellets

released by these animals may be an important source of food

for other organisms such as crabs. It has been estimated that

the ghost shrimp on approximately five miles of Sapelo Island

beach produce a collective total of 280 million pellets per day,

equivalent to 26 pounds of organic carbon per day (Frankenberg,

et al,,1967).

2. Dunes

Dunes are important to shoreline stability for at least

three reasons (Oertel, 1974):

a) barriers which prevent flooding and protect

land and structures located directly behind the beach;

b) energy dissipation whereby the energy of a wave

surge is absorbed slowly;

c) reservoirs of sand in the erosion and accretion

process.

Dunes also support one of the most complex and varied of

the island communities. The dune community is a complex system

with a number of subsystems (Oertel, 1974):

a) Berm:

The upper or landward edge of the foreshore is an area of

sand accumulation called a berm. The berm marks the upper

limit to which sand may be transported by wave action. The berm

develops seaward as gentle waves add the offshore sand bars to

the beach slope.

b) Backshore:

A developing berm broadens to form a low, flat area, or

backshore. The extent of the backshore is an indication of

how rapidly the shoreline is building.

c) Foredunes:

Periodic spring tides float dead Spartina stalks out of

the marshes and deposit them on the backshore as "beach straw".

Drifting sand trapped in this litter collects in small mounds

or foredunes. Beach straw buried in shallow sand slowly decom-

poses, thereby satisfying three factors which noimally limit

the initial colonization of dunes (Ranwell, 1972):

development of soil nutrients;

2), stabilization of substrate;

3) retention of soil moisture.

A variety of salt resistant plant species (Panicum distichum,

Distichlis spicata, Sesuvium pcrtulocastrum, for example)

rapidly colonize the new habitat. Their presence traps more

sand and stimulates further dune growth.

d) Primary dunes:

Given sufficient time (perhaps two years), foredunes

develop into primary dunes, gaining a half dozen feet of eleva-

tion and acquiring adense cover of sea oats (Uniola paniculata)

or panic grass (Panicum amarum). Plants inhabiting the primary

dunes exhibit strategies necessary for survival in a rapidly

accreting dune. As parent plants are buried, adventitious

roots develop and rhizomes are induced to upward rather than

lateral growth (Ranwell, 1972).

i@?_) Secondary dunes:

Given even more time, there is a gradual shift from

grasses to shrubs (Myrica cerifera, Yucca Sp.) and eventually

to trees (Quercus virginiana, Pinus elliotti, Bumelia tenax,

,Xanthoxylum clava-herculis). lit some point the successional

development of the secondary dune becomes a forest community.

If a high-energy beach is in equilibrium and relatively

protected from storm waves, a primary dune system can persist

directly behind the berm. Typical primary dune vegetation is

not only resistant to heavy concentrations of wind-borne salt

but, in the case of sea oats, even requires it (Woodhouse,et al.,

1968). A forested secondary dune, on the other hand, usually

needs several protective tiers of primary dunes to separate it

from excessive salt burn. Slash pine (Pinus elliotti) is a

transient member of the secondary dune community, quick to

colonize and quick to succumb to the occasional heavy storm

with its salt-laden winds. When forested secondary dunes are

found just behind the berm of a high-energy beach, the shoreline

is probably receding rapidly. On the other hand, a low-energy

river beach is usually forested to the high-water line.

f) Strategy of Dune Nutrient Cycling

The shift from a nutrient-rich foredune habitat to a

nutrient-deficient primary dune must present serious nutritional

problems for the inhabitants of the open dune community (Art,

et_@!L, 1973; Ranwell, 1974), particularly nitrogen which is not

available in airborne salt. Studies have shown that the area

surrounding the roots of beach grass (Amophila) is rich with

bacteria relative to the surrounding area. Experimental plants

with sterilized roots grew less than controls with normal

bacterial flora present. There is also a close spatial rela-

tionship between the roots of beach grass (Amophila) and

mycorrhizal fungi. Both of these strategies help to provide

limiting nutrients to the community.

g) Dune Diversity

The diversity of flora within the dune community is high

(Ranwell, 1972) for several reasons:

a) nutrients are low, thereby reducing growth rates and

competition for space-.

b) there is a diversity of habitats, augmented by salt

gradients and moisture gradients;

c) there is plenty of available sunlight.

The rate at which woody species naturally colonize a

secondary dune community is determined in large part by

browsing mammals. Rabbits on British dunes can cause a drama-

tic reduction in woody species (Ranwell, 1972). There are a

number of indications that a similar phenomenon exist for the

Georgia coastal islands:

a) deer (Odocoileus virginianus) and rabbits (Sylvilagus

palustris) are common in the dune community;

b) a noticeable browse line may be observed for palatable

woody species (Quercus, Bumelia, Persea);

c) there are extensive open areas of uncolonized secondary

dunes capable otherwise of supporting woody species;

d) Palatable seedlings are rare to absent, while unpala-

table seedlings (Pinus, Myrica) are present.

This last point indicates that natural colonization by

palatable woody species will occur when browser populations

are reduced to very low densities or eliminated for periods

long enough to allow plants to grow up above the browse 'Line.

The fact that mature specimens of palatable trees are found on

secondary dunes implies that browser populations have been

sufficiently reduced in the past.

h) Ecology of Dune Fauna

A number of visiting species utilize the dunes for feeding

and resting, but probably do not require the dunes for survival.

In this category are all species of coastal island mammals as

well as a variety of wintering birds which utilize the dune area

for seeds (finches), prey (hawks) or cover.

Several Georgia birds nest within the dune community. The

most critical of these is the gull-billed tern, an exceedingly

scar<_,e species which nests in small numbers on the backshore,

frequently in association with the least tern (Burleigh, 1958).

Other species include the black skimmer (berm), least tern

(berm, backshore), Wilson's plover (foredunes), oyster-catcher

(backshore, foredunes), and willet (foredune, primary dunes).

Skimmers and least terns have adopted a survival strategy

of nesting on the berm, particularly on isolated islets. The

advantages of reduced predation in such remote areas outweigh

the losses incurred from storms and high waters. However, these

colonial nesting species are highly vulnerable to unnatural

disturbances, realizing a high mortality of eggs and young from

excessive temperatures if adults are flushed from their nests

during the day. Every precaution should be taken to locate

these colonies and isolate them from unnecessary disturbances

by man and feral animals.

Loggerhead turtles are another Georgia species which

require natural dunes for successful reproduction (Johnson,et al.,

1971; Caldwell,et al., 1959). Loggerheads seem to do best when

nesting at the base of a well-developed primary dune ridge

(Johnson,et al., 1971) which assures an optimum location for the

eggs and the safe return of adult female and young to the water.

Other natural conditions are not as favorable. Adults and young

can become disoriented among broken primary dunes and perish.

A truncated beach may recede before the eggs have time to hatch.

A broad backshore with standing water will destroy nests

(Ragotzkie, 1959). Nesting success under natural conditions

is probably quite low but sufficient for survival of the species,

since the loggerhead seems to be a long-lived, prolific breeder.

Raccoons, sand crabs, and lethel beach conditions would normally

take a considerable toll of eggs, but the occasional year with

low predator densities and optimum beach conditions would be

sufficient for the survival of the species. Aditional pressures,

such as predation by man and feral animals, disruptive lights on

the beach at night, or the loss of a natural dune

profile by sediment stabilizing structures, produce more distur-

bance than the species can tolerate. The loggerhead is all but

gone from those Georgia island beaches with a history of develop-

ment and turtle egg harvesting

The disruption of the dune community by feral animals seems

to be a widespread phenomenon (Chabreck, 1963; Cottam, 1970;

Johnson, et al-5 1971; Ranwell, 1972), although few scientific

studies have been done to document the precise effects. Cattle

and horses do compete with native browsers, selecting palatable

plant species and affecting a shift in the community structure.

On the primary dunes, feral animals remove critical vegetative

cover needed to stabilize the dunes. The effect of pigs on

nesting loggerhead turtles is disastrous (Johnsonet al., 1971).

The dune community has developed in the absence of man's feral

animals and, therefore, can not respond in a controlled manner.

Feral animals should be prohibited from the dune community. At

present, domestic stock affect the dune communities on Cumberland,

Ossabaw, St. Catherines, and Little St. Simons Island.

3. Island Forests

The island forest has been described as a live oak-dominated

association with an abundance of sclerophyllous (leather-leaved)

broad-leaf evergreens, lianas, epiphytes, and relatively few

herbaceous plant (Johnson,et al., 1971). Because of differences

in environAmental conditions, minor species are frequently

dominant in localized areas. For example, palmetto (Serenoa

repens) is a dominant understory specieson Holocene formati-ons.

An oak-scrub association is recognized for Cumberland Island,

and a palm forest (Sabal palmetto) is a local feature on St.

Catherines Island.

Very little information is.available for the maritime

forests of Georgia coastal islands-(Johnson,_@jt al, 1971).

Unpublished floral lists exist for a number of islands. Forest

tic
Zwj

associations have been mapped for Cumberland (Hillestad, et al.,

1975), Little Cumberland (Worthington, 1973), and St. Catherines

Island (McCormick,et al., 1972). Studies dealing with functional

aspects of island forests (succession, climax, response of island

forests to physical factors, etc.) are generally lacking and

must be borrowed from work done in other coastal areas.

Theories for the existence of a live oak climax on Georgia

coastal islands (Johnson,et al., 1971) consider the modifying

effects of wind, salt, soils, fire (Laessel and Monk, 1961) and

the longevity of live oaks but no single factor seems to domi-

nate. William Bartram on a viisit to St. Catherines Island in

1773, described the terrain as a series of forested "ridges and

savannahs, [the intermediate spaces being] intersected with

plains of dwarf prickly fan-leaved palmetto [Serenoa repens]

and lawns of grass variegated with stately trees of the great

Broom-pine, and the spreading ever-green Water-oak..." (Van Doren,

1955). Bartram has given us a plausible descriptionof a fire--

dominated mosaic of burned (grasses, oaks, and large pines) and

unburned (scattered clumps of heath (Vaccinium) and palmetto)

habitat (Clement, 1971).

The historical effects of man on the ecology of coastal

island forest must not be overlooked. The islands as we know

them today could well be the result of management practices

employed centuries ago. There is abundant evidence for the

presence of Indians (4000 BP to present) and many of the island

were under cultivation from 1733 to 1860 (Clement, 1971). Fire,

cultivation practices, and the presence of range animals have

all affected the coastal islands in one way or another. At

this moment, a precise chronical of historical events and

practices for each island wouldbe a valuable aid to our under-

standing of island ecology.

Unique Forest Associations

There exist a number of unique forest associations for the

poastal islands. Some examples, familiar to the authors, will

illustrate this point.
a) Associations which are rare or unique to Coastal Georjia:

1) several hundred acres of myrtle oak (Quercus

myrtifolia) on Little Cumberland Island appear to

be an unusually large size for this rare associa-

tion. (Wilbur Duncan, pers. comm.)

2) Carolina laurel-cherry (Lycium caroliniapum),

growing on a tiny island in the Cumberland salt

marsh, is presently the only known specimen for

the state as well as the most northerly represen-

tative of the species.

3) Florida privet (Forrestiera porulosa), growing on

a narrow shell bar near Little Cumberland Island

and on the south end of Cumberland represents

examples of this little known species in the state.

b) Associations common to the mainland, but rare on the

coastal islands:

1) Tupelo swamp (Nyssa biflora) occurs as small stands

in wet drainage areas. Large trees and swampy

terrain make -these areas valuable for aesthetic

appeal and environment interpretation.

2) A nearly homogeneous palm forest on St. Catherines

Island is unusual for a coastal island, but may

be found on -the mainland.

There is a great need -'Co define and catalog the unique

forest associations on the Georgia coastal islands. The -total

area of an individual association can be less -than an acre in

extent. Small parcels of the environment are particularly

vulnerable to residential development, roads, and powerline

rights-of-way. Unique forest associations are part of the

diversity of coastal islands. Development plans must consider

these areas if only because the associations are there and are

part of the island ecosystem. Vegetation maps must recognize

these small associations.

if proper protection is afforded unusual forest associa-

tions, island forests can be ecologically tolerant of controlled

human use (Clement, 1971). Clearings in the Oak forest,

sufficiently distant from the zone of airborne salt, should

not adversely affect the forest community. Deer, turkey, and

resident song birds would probably benefit from clearings in

the forest (lawns, fairways, and grassy rights-of-way) as long

as forested buffer zones are interspersed with the clearings.

Deer and turkey are edge spec-Les, finding optimum food and

shelter along transitional environments.

4. Island-Marsh Interface

One of the most interesting communities of the Georgia

coastal islands is the island-marsh interface. A unique soil

series has developed with it (Wilkes,et al.,1974) because spring

tides flood low-lying sand soil with suspended clay and silt.

The community consists of a gradua1 continuum of subcommunities

between terrestrial forests and salt marsh. As such, the

community represents a zone of gradual change at the marine-

terrestrial interface. A number of marine organisms (crabs)

and terrestrial organisms (birds, mammals, reptiles, insects)

are able to cross such a gradual boundary and have acquired the

ability to utilize resources from both marine and terrestrial

habitats.

The island-marsh interface is a dramatic example of plant

zonation. The critical factor is elevation, affecting frequency

and duration of tidal flooding, evaporation rates, soil texture,

salinities and temperature. The island-marsh interface commun-

ity provides a fascinating opportunity for studying the ecology

of limiting factors and plant distribution. For instance, the

upper extent to which cord grass (Spartina alterniflora) can

grow in the interface community seems to be limited by an iron

deficiency. Salt grass (Distichlis spicata) and black rush

(Juncus roemerianus) are not limited by iron, grow higher in

the community, and are ultimately limited by other factors

(Adams, 1963).

100

Values and Vulnerabilities of Island Communities

1. The high-enery beach community is naturally resistant

to the physical pounding of surf. Such a community

will also be unaffected by a similar impact of heavy

pedestrian traffic. The beach is intolerant to chemi-

cal disturbance, however, and would be expected to

react adversely to chemical pollution.

2. Low-energy beaches are high in organic sediJtents, high

in diversity and abundance of beach fauna, but low in

desirability as a recreational beach. These beaches

should receive priority as wildlife habitat.

3. Dune communities are resistant to salt and wind but

not to the di5turbing effects of pedestrian traffic

on vegetative cover.

4. The colonizaticn of secondary dunes by woody plants is

affected by browsing mamnials. The exclusion of deer

and rabbits, from secandary dunes would be expected to

stimulate colonization by oaks and other palatable

tree species,

.5. Colonia-I nesting birds are particularly vulnerable

Lo human disturbance. Successful colonies will be those

which are protected by a wide buffer zorte.

6. Dunes and beaches are dynamic syEtems which cannot be

stabilized without loss of the community. Nesting

habitat for loggerhead turtles and sea birds has been

lost on islands with stE.bilized beaches.

101

7. The forest community seems to be resistant to the impact

of low-denS4ty residential housing and many forms of
L

outdoor recreation.

Summary

One very important theme occurs throughout this paper:

The understanding of coast.alterrestrial ecology depends on an

awareness of differences (Table3-'2); differences in physical

conditions, differences in community response, differences in

survival strategy. Coastal island differ from the mainland.

Holocene islands differ from Pleistocene islands. To a lesser

extent, one Pleistocene island will differ from another.
L _L

The adjacent mainland, the Pleistocene island. and the

Holocene island represent an environmental continuum from old

and mature to young and rigorous. "Old", l'young", "mature",

and "rigorous" are relative terms which derive from the predom-

inant geological age of the formation being considered. Added

to the geological effect is the rather abstract concept of

insularity and the tendency for the unit land mass to decrease

in size from mainland to Pleistocene island and from Pleistocene

island to Holocene island. Both insularity and decreasing size

add to the ecological rigorousness of the enrivonment.

Items 1 through 4 (Table 3-2)represent physical charac-

teristics of the system which are primarily regulated by the

geology and climate of the coast. These factors intensify along

the physical gradient from mainland to Holocene island. The

predictability of available water and fluctuations in the water

102

table are physical characteristics whichare related to volume

and texture of the subsoil, rainfall, and drainage. Similarly,

the diversity And maturity df soils relates to the manner in

which the subsoil layers were depositied and the age of the

deposits.

The concept of an abiotic continu um, varying 'from "receptive"

(mainland) to "resistent'l-Molocene island), refers to the

facility witb which the biotic community can adjust to the

physical environment. It is on this abiotic continuum that the

community response is superimposed.

Item 6 is a descriptive fact, while items 7 through 11 are

functional responses of the community to the abiotic environment,

including vulnerability to damaging fires, stability of nutrient

cycles, impact of insularity, response of animal populations to

changes in the community. In all of these examples, a commun-

ity will respond according to its location on the continuum.

In other words, Holocene communities would be expected to

react most violently and be most damaged by unnatural distur-

bances in the environment, while Pleistocene communities will be

damaged to a lesser degree, and mainland communities least of

all.

Differences between Pleis--ocene islands or between Holocene

islands tend to be descriptive and not functional. A prograding

beach on Blackb--e-ard Island may look strikingly different from a

receding beach on Wassaw Island, and the species composition of

the two communities may be very different. The manner in which

ltv.l
WO

Table 3-2

Physical Factors and Functional Responses of
Selected Coastal Communities

FACTOR ADJACENT PLEISTOCENE, ISLAq, ri-6 HOLOCENE
MAINLAND WrIH ISLANDS
HOLOCENE DFPQSITS---
1. Predictability
of available HIGH W4
groundwater,
2. Oscillations in MODERATE EXT=
the water table

3. Diversity of
soils HIGH

4. Maturity of
soils OLD YOUNG

RECEPrIVE RESISTENT
5. Abiotic conditions TO BIOTIC BIOTIC
DEVELOP= DEVELOR4W

6. Vulnerability to
damaging fires LESS MORE

7. Stability of
nutrient cycles HIGH LOW

8.Impact of insularity NONE
9. Species diversity 10W
of flora & fauna HIGH

10. Response of animal
populations to changec,
in the corruminity MODERATE SEVER1,'

11. PrK)bability of
irreversible changes HIGH
to the community LOW

104

the two communities respond, however, to the physical changes

in the beaches should be functionally similar. We should be able

to predict the community response of one island based on our

knowledge of the other island, in spite of initial differences

in the species composition of the two islands. We should also

predict that descriptive differences could disappear if physical

conditions between the two islands become similar.

Given this overview of the functional aspects of island

ecology, however cursory or incomplete, we are in a position to

improve our understanding of the ecology of Georgia barrier

islands. A number of suggestions can be made:

1. An inventory of natural resources:

The application of ecological principles to specific

island conditions requires facts. A comprehensive analysis

of Georgia island ecology will require more data than is

presently available. There is a need for additional soil

maps, nutrient maps, vegetation maps, a catalog of forest

associations, faunal descriptions, and measurements of the

Intensity and duration of a number of physical forces

acting on the community. An historical review of man's

activities on the coastal islands would be an important

part of this inventory.

2. Sample size:

One very important project is to determine the minimal

portion of the ecosystem needed to describe ah environ-

menta'L attribute. For example, the description of nutrient

1^0
VU

cycling on twenty linear feet of primary dune ridge may

provide all the information needed to extrapolate to the

remainder of the primary dune system. The study of a

deer population would require as the minimal study unit an

area equal to the size of the island. Some highly mobile

species may have to be considered at the coastal ecosystem

level. In preparing maps, the scale of resolution of the

map must be adequate to represent the minimal unit of the

subject being studied.

3. Develop functional understanding:

An improved data base would provide needed information

for increasing our understanding of basic ecological

functions on Georgia coastal islands. Some of the strate-

gies discussed in this paper are conceived for communities

quite different from the Georgia coastal islands. The

predictive value of these strategies is limited by the lack

of substantiating studies and local data from the Georgia

coast.

4. Update ecological surveys:

As the understanding of Georgia island ecology develops,

evaluations such as this report should be conttinuously re-

examined and refocused on critical issues. This, in turn,

would initiate a form of positive feedback for defining

further ecological studies.

5. Predictive models:

A major step in environmental analysis the Georgia

106

islands would be the development of predictive models.

Models require a rigorous understanding of community func-

tion as well as a complete resource inventory. Predictive

models would permit a better understanding of old questions.

For instance: How much disturbance should an island be

allowed to absorb before disturbances reach damaging levels?

How natural are the coastal islands? How changed are they

by the effects of man, historically and at the present?

6, Management guidelines:

Answers to questions like the above provide a strong

platform for establishing management procedures. Ultimately,

ecological priorities car.. be integrated into all levels of

the coastal land use plan.

107

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Johnson, A. S., Hillestad, H. 0., Fanning, S. A., and Shanholtzer,
G. F., 1971, An ecological survey of the coastal region of
Georgia: U. S. Dept. o .f the Interior, National Park
Service, 387 p.

Kahl, M. P., 1964. The food ecology of the wood stork: Ecologi-
cal Monographs. Vol. 34, p. 97-117.

Komarek, E. V., 1973, Introduction to lightning ecology: Proc.
Annual Tall Timbers Fire Ecology Conference, Vol. 13,
p. 421-427.

Laessle, A. M.,and Monk, C. D,, 1961, Some live oak forests of
north-eastern Florida, Jour, Florida Acad. Sci,., Vol, 24,
no. 1, p. 39-55.

Lewis, W. M., Jr., 1974, Effects of fire on nutrient movement
in a South Carolina pine forest, Ecology, Vol. 55,
p. 1120-1127.

MacArthur, R., and Wilson, E, 0., 1967, The theory of island
biogeography: Princeton, N. J., Princeton Univ, Press,
203 p.

Martin, W. E., 1959, The vegetation of Island Beach St4te Park,
New Jersey: Ecological Monographs, Vol. 29, no. 1, p. 1-42,

McCallie, S. W., 1908, A preliminary report on the underground
waters of Georgia: Georgia Geol. Survey, Bull. 15', 370 p.

McCormick, J., Somes, H. A. and Ashbaugh, T. R., 1972, Vegetation
of St. Catherines Island, Ga.: New York, Am. Museum of
Natural History, 46 p.

Odum, E. @P. , 1971, Fundamentals of Ecology: Philadelphia,
W. B. Saunders Co., 574 p.

Odum, H. T., and Caldwell, D. K., 1955, Fish respiration in the
natural oxygen gradient of an anaerobic spring in Florida:
Copeia, Vol. 2, p. 104-106.

Oertel, G. F., 1974, A review of the sedimentologic role of dunes
in shoreline stability, Georgia coast: Bull. Georgia Acad,
Science, Vol. 32, p. 48-56.

Pomeroy, L. R., 1959, Algal productivity in salt marshes of
Georgia: Limnology and Oceanography, Vol 4, no, 4,
p. 386-397.

110

Ragotzkie, R. A., 1959, Mortality of loggerhead turtle eggs
from excessive rainfall: Ecology, Vol. 40, no, 2,
p. 303-305.

Ranwell, D. S., 1972, Ecology, of salt marshes and sand dunes:
London, Chapman and Hall Ltd.,, 258 p.

Remezov, N. P., and Pogrebnyak, P. S., 1969, Forest soil
science: U. S. Department of Commerce, Springfield,
Virginia, 268 p.

Van Doren, Mark, 1955, Travels of William Bartram;. New. York,
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Ward E., 1942. Phragmites management: Trans. 7th N. Amer.,
Wildlife Conf. p. 294-298.

Wilkes, R. L., Johnson, J. H., Stoner, H. T., and Bacon, D, D.,
1974, Soil survey of Bryan and Chatham counties, Georgia:
Washington, D. C., U. S. Dept of Agriculture, Soil
Conservation Service, 71 p.

Woodhouse, W. W., Jr., Seneca, E. D., and Cooper, A. W., 1968,
Use of sea oats for dune stabilization in the southeast:
Shore and Beach, Vol. 36, p. 15-21.

Worthington, J., 1973, An evaluation of environmental impact
on Little Cumberland Island, Ga.: Unpub. Masters Thesis,
University of Massachusetts.

CHAPTER 4

the Value and Vulnerability
Of
Fresh Water Ecosystems

David M. Gillespie
Department of Zoology
Georgia Institute of Technology

Introduction

The major sources of fresh water in the coastal counties

of Georgia are five river systems; the Savannah, the Ogeechee,

the Altamaha, the Satilla and the St. Marys. Other fresh

waters include small streams arising in the coastal counties,

direct precipitation and ground water. This report is pri-

marily concerned with the major river systems, since these

are ecologically most important in the area. These rivers

fall into two typesi those that rise in the coastal plain and

those that rise in the piedmont. The former, which include

the St. Marys and Satilla, are blackwater streams which are

acidic andcontain large amounts of humic acids and other

113

dissolved organic matter, and are very low in other dissolved

and soluble solids. The other rivers, which derive at least

part of their flow from the piedmont, tend to be higher in

dissolved solids, and are better buffered, thus much less acid.

All, however, flow through extensive swampy areas and tend to

be high in organic matter. Although these streams differ in

some respects, they share many characteristics, and the values

and vulnerabilities of their ecosystems are common to all.

Some of the values of fresh water ecosystems are clear

and economically obvious while others are more subtle and are

difficult to evaluate in terms that are clear to laymen. Some

of these values are directly assessible in terms of the fresh

water ecosystems, while others may be assessed only by indirect

effects on other systems. Direct values include human uses of

water such as domestic, agricultural and industrial consumption,

as well as recreationalaesthetic and educational values. In-

cluded in the latter group are the production of fish and wild-

life; the production of aquatic plants and invertebrates, which

serve as food for fish and other animals; boating, including

floating and canoeing; and the uses of the river for research,

teaching and other educational needs. Less obvious, but at least

equally important, is the function of the fresh water ecosystems

in purifying and reaerating waters which have been sub@ected to

human use and contamination. Indirect values include the effect

of the rivers on the surrounding water tables, and the effects

which occur at the fresh water - salt water interface in coastal

1114

estuaries. The latter include the transport of sand and

nutrients by the rivers, and the flushing action of high fresh

water flows on the estuarine systems. Not only total flows,

but the regime, or periodicity and pattern of flow, appear to

be important in this respect.

All of these values are vulnerable to disturbances brought

about by natural changes or by the unwise or poorly planned

activities of man. The major human disturbances, all of which

have already occurred to some extent or other in coastal

streams, include pollution from agricultural, domestic and,

industrial sources, cutting of' river swamps and flood plain

forests, damming, and channelization of the streams. Further

disturbances of these types must be kept to a minimum, and,

where-further disturbance is absolutely necessary, the burden

of proof should be placed upon those advocating disturbance.

Coastal Georgia is fortunate in having abundant and, as yet,

relatively clean and unpolluted sources of fresh water. To

permit the profligate destruction of this source would be a

tragedy.

Direct Values: Stream Channels

The channels Qf the major streams are important sources

of water for domestic, supply, industry and agriculture, includ-

ing waste disposal. These channels and the ecosystems which

they support also provide important recreational, aesthetic,

and educational values. In spite of their obvious and growing

importance, or perhaps partially because of it, these stream

115

channel ecosystems are especially vulnerable to disturbance.

Those uses of water which create major disturbances, such as

pollution, the construction of dams, and channelization, are

primarily concentrated in the stream channels, although these

disturbances inevitably affect the flood plain and river swamp

ecosystems to an equal or greater extent. Ecological destruc-

tion is thus likely to be greatest upon this part of the system

which is most used and appreciated by the human population.

Sport fishing is a pastime which is enjoyed by hundreds

of thousands of Georgians and many visitors to the State every

year. The economic value of sport fishing, which supports-a

multi-million dollar industry, is clear, and the value to the

participants in terms of recreation and aesthetics may be

even more important. Georgia's coastal rivers support many

species of sport fishes, both resident fresh water species and

anadromous species which enter brackish or fresh waters to

spawn (Dahlberg and Scott, 1971). The relative importance of

the marine, fresh water and anadromous species in the catch of

residents and visitors in the coastal counties is not entirely

clear, but the concentration of fishermen along the stream

channels is certainly significant. Fresh water residents which

are important sport fish include pickerel, several species of

catfish, several sunfishes, crappie and, the most sought after

of Georgia fresh water fishes, large mouth bass. These fishes

live and feed in the river channels, and many spawn there as

well. In addition, there are many smaller forage fish

116

which also live in the rivers, and which are important as

food for the larger game species (Dahlberg and Scott, 1971).

Several species of salt water fishes enter the river channels

to spawn, and some of these anadromous forms are important in

sport and commercial fisheries (Carley and Frisbie; Smith,

1968). Striped bass are an especially important sport fish,

and American shad and hickory shad are seasonally important

as sport and commercial fishes. In addition, the blueback

herring may be of some importance commercially.

In addition to the true anadromous fishes, many salt

water species penetrate the river mouths to a greater or

lesser distance to feed. These include red drum, spot, mullet,

southern flounder, hogchoker, spotted trout, pipefish, and

needle fish (Dahlberg and Sco--t, 1971; Georgia Game and Fish

Commission, 1968). There are probably other species which

penetrate into the river channels at some time or other, as

well as many which depend upon the brackish waters maintained

by fresh water flows.

It is clear that disruption of the habitat adversely

influences the movement and production of fishes in streams.

The placements of dams, or other structures which act as barriers

to fish migration can disrupt the life cycles of fishes, in-

crease mortality rates and destroy the clues and signals which

fishes depend upon to guide them in their movements (Northcote,

1967). It is also clear that channelization of streams reduces

cover and habitat diversity, and thus results in decimation

117

of fish populations (Bayless and Smith, 1965; Wharton, 1970).

In addition, stream channels which have been channelized and

straightened tend to resume their former meandering, thus

increasing bank erosion and siltation, and further degrading

the fish habitat (Russell, 1967; Leopold, etal., 1964). Fish

are remarkable resilient creatures, and so the fisheries are

seldom completely destroyed, but serious degradation may take

place with even relatively minor disturbance.

In addition to the fish populations themselves, the

stream channel ecosystem of which they are a part includes a

great variety of other organisms which interact to form a

dynamic stream channel community. This community forms the

ultimate biological basis for the production of game and non-

game fish species (Gerking, 1967; Hynes, 1970). The important

organisms in such communities may include bacteria, many species

of algae, higher aquatic plants, a large and diverse insect

fauna, fresh water snails and mussels, and numerous other

aquatic invertebrates. These inconspicuous, but nonetheless

important species may be more vulnerable to pollution and other

disturbance than the fishes themselves (Gaufin, 1973). Any

change in the aquatic environment results in a corresponding

change in the communities of aquatic organisms, and these

changes are inevitably transmitted through the food chain to

the fish populations. Thus, a degree of disturbance which may

seem minor will nevertheless result in a change in numbers and

kinds of aquatic organisms. The result of a small disturbance

may not be immediately obvious from our point of view, but is

nonetheless real, and the cumulative effect of many small dis-

turbances is ultimately expressed as a major change in the

populations of fishes and other aquatic organisms. It is

important that we be aware of such changes, and that we develop
CD

methods of assessing them and determining whether they are of

such significance as to negate the beneficial effects of

"improvements" which are be--'-ng imposed'upon the stream channel.

The flow of energy through the river swamp -is schematically

shown on Figure 4-1.

It has been suggested that blackwater streams are extremely

unproductive (Janzen, 1974), but -this does not seem to be the

case in the blackwater streams of Georgia. The preliminary

results of research now being pursued by Dr. A. C. Benke and

me in the Satilla River, as well as a survey by the Environ-

mental Protection Division, Georgia Department of Natural

Resources (1973), indicate 1--hat the opposite may be true. The

Satilla appears to support a fairly good fishery, as estab-

lished by State Game and Fish Division research (Sandow, et al.,

1973; 1974), and the basis for thiq lies in vast numbers of

tiny filter-feeding insects and crustaceans which trap bacteria

and detritus carried by the stream. These tiny filter-feeders

are fed upon by predacious insects and small fish, and these

in their turn are consumed by large fish. Dead trees and

branches, which are numerous in undisturbed stream channels,

form a major habitat for bo---h filter-Ifeeding and predacious

119

species. These "snags" are often covered with thousands of

small vertebrate animals. It is probable that 2/3 - 3/4 of

the biomass of stream invertebrates is to be found on dead

snags. The ultimate source of energy for this aquatic community

appears to be the river swamps which line the banks of much of

the Satilla River. Such small filter-feeders are probably-of

.great importance in other streams as well, and in addition to

providing food for larger organisms, they are of great signifi-

cance in the natural purification of waters which have been

polluted. The living part of the ecosystem is necessarily an

important factor in the use of running water for waste disposal,

since pollutants added to water must be broken down by bacteria,

and these bacteria, along with remaining detritus, are removed

and consumed primarily by small filter-feeding insects and

other arthropods (Hynes, 1960, 1970). The maintenance of a

rich and diverse community of aquatic invertebrates is thus

of great significance to both the productivity of streams and

to their ability to absorb and metabolize pollutants.

Other forms of wildlife are also supported by Georgia's

coastal rivers. Species such as deer, raccoon, squirrels and

many others may derive direct or indirect benefit from the

stream channels. Many aquatic birds are directly dependent

upon the stream ecosystem for support, including huntable wild

fowl as well as many non-game species. Bird watching, or

"birding", while not as popular in Georgia as hunting and

fishing, is a pastime enjoyed by a large and growing segment

120

of the population. This and other forms of nature study com-

prise an increasingly important recreational use of our rivers.

Such non-destructive use of resources should be encouraged

and the increased tendency to introduce grade school, high

school and college students to nature study in a more or less

formal context will certainly have this effect. The coastal

rivers used in this way, are thus an educational resource that

can produce profound effects extending far beyond their banks.

A. few hours spent collecting and. stuuying the living 7@oosysterqs

of a clear flowing river is an experience that a student may

remember for the rest of his life. Perhaps equally important

is the use of our rivers as a resource for research. Informa.-

tion gained from study of Georgia's coastal river systems can

be extrapolated and extended to apply to other streams and

other types of ecosystems, arid, perhaps even more significantly,

graduate students who receive their research training in the

course of such investigations are able to enter society as

teachers and scientists and apply the knowledge gained in a

broad variety of fields.

The sport of canoeing down rivers is usually associated

with the upland streams of northern Georgia, but the coastal

rivers also offer many opportunities for this sport. Although

they lack the spectacular rapids and falls of the north Georgia

streams, they are, in their own way, equally beautiful and

fascinating. Drifting gently between banks lined alternately

with upland -trees and swamp forests, with occasional stretches

121

Figure 4-2-

Energy Flow Relationships
"Wow
of River Swamp -
River Channel
Ecosystems

river swamp river channel
swamp forests
ajT &
detritus aquat plants
fungi & bacteria filter feeders grazers
I i i
benthic smal I predators
detritivores go (insects, small fish)
i
larger fish

Not to scale.

Source: Dr. D. Gillespie, Georgia Institute of T,--chnology.

122

of somewhat swifter water and occasional detours into swampy

backwaters among cypress trees, can be a rich and fascinating

experience. The swift excitement of the mountain streams is

more than compensated for by the increased opportunities to

relax and watch the abundant wildlife along the shores. Some

effort has been made 'to promote canoeing as a sport, particu-

larly on the Satilla River. Efforts include the report by

Hanie and Hay (1969) and a set of detailed maps of the river

between Waycross and Woodbine. Other coastal streams may be

equally attractive, and should see increased utilization in

the future if their aesthetic value is not destroyed by other

practices.

Direct Values: River Swamps

The separation of the flood plains and river swamps from

the stream channel is an artificial one, justifiable only as

a convenience. They are in reality inseparable, and distur-

bances which affect one inevitably affect the other. There

are, however, many values whi;2h can be attributed to the river

swamp-flood plain part of the system, as has been ably pointed

out by Wharton (1970).

Although swamps have bee.-a traditionally regarded by man

as unhealthy and unattractive, there is an increasing apprecia-

tion of the aesthetic value of river swamps and more extensive

swampy areas as well. The swamp as a place of beauty, and as

the home of an abundant variety of wild animals and plants, is

123

increasingly appreciated by an urban population disgusted with

pavement and smog. On the other hand, there is still- plenty

of pressure to drain and develop swampland and other flood plain

areas for housing and industrial sites and agriculture. Quite

apart from the inconvenience of having thei@e developments dam-

aged or even destroyed by floods every few years.; such projects

are usually ecologically disastrous.

In many streams the major energy source for the ecosystem

is allochthonous organic matter, or organic matter produced

beyond the immediate conf ines of the s tream, and the coastal

river systems are no exception to this (Cummins, 1973). The

river swamps are perhaps the most important single source of

t 4
energy for the aqua _Lc ecosystem. This energy enters the

streams in the form of leaves, bark and other particulate mat-

ter and as dissolved and colloidal organic matter. This

organic detritus accumulates on -the forest floor during low

water and is picked up and swept into the main channel during

floods. It is to some extent replaced by nutrient-rich silt,,

deposited when swift channel waters, laden with sediment, over-

flow the banks and drop much of their suspended load as they

flow more slowly over the flood plain. The detritus is attacked

and broken down by aquatic bacteria and fungi, either on the

flood plains or in the river channel. Bacteria, fungi and

detritus are in turn consumed by aquatic insects and other

invertebrates, either on -the bottom or after being filtered

from the moving water. These invertebrates are then fed upon

124

by larger animals, as mentioned above (see Figure 4-1). The system

is vulnerable to any interference with this detr4tal food chain

and to any interruption of the regular ebb and flow of flood

aaters. The components of the river swamp ecosystem during low

;qater and during flooding are sc'.'Iematically shown on Figures 4-2

and 11-3.

River swamps and small lakes or sloughs which they often

contain can also be productive in other ways. River swamp lakes,

trapped when the water goes down, often develop a rich flora and

fauna of their own and may supply plankton and other organisms

to the river when connected to the main stream during high water

(Hynes, 1970). Such lakes and sloughs may also be of great

importance as nursery and spawning grounds for many river fishes,

and without the periodic flooding, isolation and reflooding of

such sites, these species disappear from the streams. There

are many species of both fish and invertebrates which are more

or less confined to swamps and backwaters and which are elimi-

nated by draining and channelization (Gilbert, 1969; Hynes, 1970).

For the river ecosystem, the river swamp is thus an integral

part, serving as habitat for some organisms, spawning and nursery

grounds for others, and a major food source for all. It is

nonsense, therefore, to speak of draining and filling the swamp

while. preserving the beauty and other values of the river. A

stream channel may be preserved, perhaps even with some values

retained, but the river ecosystem will have been destroyed.

125

Figure 4-2

Components
of the River Swamp
Ecosystem
During Low Water*

swamp forest willows, etc.
trees

detritus young fish
tadpoles
insects

low
water

snags

-slough- -levee-

river swamp channel sand bar-

Organic matter accumulates on the forest floor where it is
decomposed by bacteria and fungi. Young fish, tadpoles,
insects and other organisms mature in sloughs and ponds,
which are like protected "nursery" areas. Willows and
other vegetation help to stabilize the sand bar. Snags,
composed of dead trees and branches, help stabilize the

channel and provide a habitat for many small animals.

Not to scale.

Source: Dr. D. Gillespie, Georgia Institute of Technology.
126

Figure 4-3
Components
of the Friver Swamp
Ecosystem
During Fidoding*

%J I

ft hk3h
er

snags

kslough-1 @-ievee-
river swamp channel I.sand bar-

During periods of flooding, the detritus (bacteria, fungi
and decomposed organic matter) is washed out of the swamp into
the river channel. It is partially replaced by silt from the
river. Fish move into the slcughs to spawn in protected
waters. Young fish and other animals swim or are washed into
the main channel.

Not to scale.

Source: Dr. D. Gillespie, Georgia Institute of Technology.

127

Indirect Values

The major indirect values of the fresh water systems of

coastal Georgia include those effects which occur at t'lle fresh

water-salt water interface in estuaries, involving transport

of water, nutrients and other material, and effects on the

water tables surrounding the coastal rivers. Estuarine systems

are strongly affected by the- inflow of water and the dissolved
CD

and particulate matt-er car-nied with it and also by the periodi-

city of such inflow. The substrata of the coastal area of

Georgia are generally rather porous and as a result the fresh

water levels in rivers and swamps may have a significant effect

on level and flow of ground water.

Brackish estuarine waters are of great importance as

spawning and nursery grounds for many species of marine fish

and invertebrates and they are also important as feeding

grounds for adults of many species (Remane and Schleiper,

.1971). Several species are of major economic importance in

coastal Georgia (Carley and Frisbie, 1968). These include blue

crabs, oysters, shrimp and several important species of fish.

In addition, these estuaries support a great variety of plank-

tonic Dlants and animals upon which the larger economically

important species depend for sustenance. This estuarine eco-

system depends upon a regular, but periodically varying., supply

of fresh water from the coastal rivers, and any disturbance of

the river svst.em is likely to affect the amount, periodicity

and quality of this fresh water supply. Past disturbance has

128

already been felt, both economically and ecologically. Oysters

for instance, which were formerly abundant all along the Georgia

coast, have been greatly reduced in recent years as a result.

of pollution, unstable substrate, fouling and othE@r factors

(Carley and Frisbie, 1968). There is evidence that other

species, including anadromous fishes, have also been adversely

affected (Smith, 1968; Adams, 1970). Various distrubances of

the fresh water rivers are responsible for these changes. Chem-

ical pollution has adversely affected many species of aquatic

animals and plants; changescf land use in watersheds, including

deforestation and filling of river swamps, have affected sedi-

ment transport and a variety of stream biota; and damming and

channelizat-Lon have affected stream flow regimes, sediment

transport and movements of fishes and invertebrates. Further

disturbances along these lines can be confidently expected to

have additional adverse effezts on the coastal ecosystem.

Fresh water rivers are -the ultimate source of mineral

nutrients for coastal and near shore marine ecosystems although,

in general, they do not necessarily provide for the immediate

"fertilizer" needs of estuaries (Filey, 1967; Odum, 1971).

Estuaries tend to concentrate nutrients and organic matter and

to export organic and inorganic nutrients to the waters further

offshore. The flushing action of fresh waters flowing through

the estuaries, thus fertilizing offshore systems, may be more

important than the direct input of nutrients. ThE near shore

accumulation of nutrients, or eutrophication, has become a

129

serious problem in some areas (Ryther and Dunstan, 1971). Both

the small but growing input of nutrients from the fresh waters,

and their flushing action in moving accumulated nutrients out

to sea are thus of great importance.

A factor which has not received enough attention from

biologists and engineers is the periodic nature of fresh water

flows. Streams vary greatly in discharge during the course of

a year, so that a very high percentage of total water and sedi-

ment transport may occur within a very short time. There are

also variations in flow from year to year, and the time of peak

flows is also variable. It is generally assumed in engineering

circles that a reduction in this periodicity is beneficial, and

this is often incorporated into the design of dams and other

structures. While dams may reduce the magnitude of fluctuation

in stream regime, channelization is more likely to increase it.

A frequently seen pattern is the draining and channelizing of

upstream areas, followed later by the construction of dams

downstream to control the resulting increase in peak flooding.

In Georgia's coastal river systems the river swamps tend to

control and slow the downstream travel of flood peaks, reducing

the amplitude of the flood stage and spreading it over a longer

time. Iniat least two major river systems, the Altamaha and

Savannah, dams have been constructed above the fall line which

affect the stream regimes. The coastal ecosystems, both fresh

water and salt water, have been adapting for millenia to these

natural fluctuations. A major part, in some cases possibly all,

130

of the flushing action of water flows through the coastal

estuaries takes place during periods of high water. Reduction

of peak flows may result in an acc.umulation of nutrients and

an increase in the already serious eutrophication of estuarine

ecosystems. It is reasonable to hypothesize that, in at least

some areas, the increased fouling and oversettli,ng which has

helped destroy the once abundant oyster' beds of the Georgia

coast has been the result of decreased peak fresh water flows

with their accompanying flushing action. The effects on

coastal ecosystems of tampering with the flow of fresh waters

is not well understood, and unt il a great deal of more infor-

mation is available, additional modifications of this type

should be approached cautiously and only after careful study.

The life cycles of aquatic organisms involve periodic

phenomena that may be closel- dependent upon the periodicity
Y

of water flows, and these animals may be affected in unpredict-

able ways (Remane and Schliaper, 19711; Georgia Game and Fish

Commission,, 1968).

Vulnerabilities

The fresh water ecosystem is a dynamically balanced

system maintained by the interactions of physical and chemical

environment with the flora and fauna of the biological commun-

ity. It is vulnerable to any changes which disrupt these

interactions. It is, howeve:-, a resilient system and capable

of resisting and recovering from disturbances.

Physical changes to which the system is vulnerable

131

include those such as dams, channelization and watershed modi-

fication. Other physical vulnerabilities involve river swamp

filling and dredging and increases in sediment loads in streams.

Chemical factors which may be affected include nutrient inputs,

changes in water chemistry, release of toxic chemicals, increases

of organic load from domestic, agricultural and industria-1

sources, and, especially in the coastal area, salinity changes.

Biological vulnerability may involve interruption of energy

flows, as by destruction of swamp forests, disruption of detri-

tus transport, or removal of important parts of the aquatic

flora and fauna. There may also be interference with life-

history phenomena, such as,occur when species are denied access

to breedingareas in streams or in ponds and sloughs, when

migrations are interrupted, or when feeding grounds and essen-

tial cover are disturbed. The communities may also be disrupted

by extermination of some species or by the unwise introduction

of undesirable exotic species.

It is impossible toidentify, with the present state of

knowledge, the precise effects of a given level of disturbance.

The ecosystem is complex, incorporates many time lags and

compensation factors, and is, to some extent, unknown, at

least in any quantitative way. Some research has been done

or is now proceeding, but unanswered questions abound.

The vast areas between the rivers, where swamp forest, fresh

water marsh and salt marsh meet and intermingle, are virtually

unknown. Even in the relatively well- studied estuaries many

132

problems remain. Basic research is needed into water chemistry,

life histories and distribution of organisms, response of p6pu-

lations to gradients of environmental variables, and interactions

among populations of organisms in communities. Applied problems

include the effects of changing rates and periodicity of water

flow, biological effects of chemical changes, and ways of com-

pensating for or correcting changes which have already occurred.

The primary need for basic research, along with the development

of applications to specific prcblems, should receive high

priority in coastal Georgia.

133

SELECTED BIBLIOGRAPHY

Adams, J. G., 1970, Clupeids in the Altamaha River, Georgia:
Atlanta, Georgia Game and Fish Commission Contribution
Series no. 20.

Bayless, J., and Smith, W. B., 1965, The effects of channeliza-
tion upon the fish populations of(lotic waters and eastern
North Carolina) North Carolina Resource Commission, Division
of Inland Fisheries.

Beck, K. C., 1972, Sediment-water interactions in south Georgia
rivers and estuaries: Atlanta, Georgia Institute of Technology,
Environmental Resources Center.

Carley, 0. H., and Frisbie, C. M. , 1968, The blue crab, oyster,
and finfish fisheries of Georgia--an economic evaluation:
Atlanta, Georgia Game and Fish Contribution Se@ries no. 12.

Cummins, K. W., 1973, Tropic relations of aquatic insects: Ann.
Rev. Entomol., Vol. 18, p. 183-206.

Dahlberg, M. D., and Scott, D. C., 1971, The freshwater fishes
of Georgia: Bulletin Ga. Acad. of Science, Vo. 29, p. 1-64.

Dennis, W. Michael, and Batson, Wade T. , 1974, The floating log
and stump communities in the Santee Swamp of South Carolina:
Castanea, Vol. 39, no. 2, p. 166-170.

Environmental Protection Division, 1973, Satilla River basin
study: Atlanta, Georgia Dept. of Natural Resources, 65 p.

Gaufin, A. R., 1973, Water quality requirements of aquatic insects:
Washington, D. C., U. S. Environmental Protection Agency
Rpt. no. EPA-660/3-73/004.

Georgia Game and Fish Commission, 1968, Coastal region research
activities (final report): Atlanta, Project F-20-R-3,
7-1-67 to 6-30-68.

Gerking, S. D. (ed.), 1967, The biological basis of freshwater
fish production: Oxford and Edinburgh, Blackwell Scientific
Publication, 495 p.

Gilbert, R. J., 1969, The distribution of fishes in the central
Chattahoochee River drainage: Auburn, Alabama, Auburn
University, unpublished M. S. Thesis.

Hanie, R. and Hay, M., 1969, Satilla - a report of the Satilla
River expedition 23-25 May, 1969: Georgia Natural Areas
Council and the Slash Pine Area Planning and Development
Commission, 82 p.

134

Hynes, H. B. N., 1960, The biology of polluted waters: Toronto,
University of Toronto Press.

----- 1970, The ecology of running waters: Toronto, University
of Toronto Press.

Janzen, D., 1974, Tropical blackwater rivers, animals and mast
fruiting by the Dipterocarpaceae: Biotropia, Vol. 6,
no. 2, p. 69-103.

Leopold, L. B., Wolman, M. G., and Miller, J. R.,.196,4, Fluvial
processes in Geomorphology: San Francisco, W. H. Freeman
and Co., 522 p.

Nelson, D. J., and Scott, D. C., 1962, Role of detritus in the
productivity of a rock-outcrop community in piedmont stream:
Limnology and Oceanography, Vol. 7, p. 396-413.

Northcote, T. G., 1967, The relation of movements and migration
to production in freshwaterfisheries in Gerking, S. D.
(ed.), The biological basis of freshwaTe-r fish production:
Oxford and Edinburg, Blac'<well Scientific Publications,
p. 315-344.

Odum, E. P., 1971, Fundamentals of ecology, 3rd ed.: Philadelphia,
W. B. Saunders, Co., 574 p.

Pilkey, 0. H., and Frankenberg, D., 1964, The relict-recent
sediment boundary on the 3eorgia continental shelf: Bulletin
Ga. Acad. Science, Vol. 22, p. 37-40.

Remane, A., and Schlieper, C., 1971, Biology of brackish waters'*
New York, John Wiley and Sons, Inc., 372 p.

Riley, G. A., 1967, Mathematical model of nutrient conditions
in coastal waters: Bull. of Bingham Oceanography, Vol. 19,
p. 72-80.

Russell, R. J., 1967, River plains and sea coasts: Berkeley,
Univ. of California Press, 173 p.

Ryther, J. H., and Dunstan, W. M., 1971, Nitrogen, phophorus
and eutrophication in the coastal marine environment:
Science, Vol. 171, p. 1OC8-1013.

Sandow, J. T., Jr., and McSwain, L. E., 1973, Population studies
streams - Satilla River drainage in Final report: State-
wide fisheries investigations: F-21-5, 7/l/72-6/30/73.

Sandow, J. T., Jr., Holder, D. R. and McSwain, L. E., 1974,
Life history of the red breast-- sunfish in the Satilla River,
Georgia: 28th Ann. Conf. S. E. Assoc. Game and Fish
Commissioners.

125

Sepkoski, J. J., Jr., and Rex, M. A., 1974, Distribution of
freshwater mussels: coastal rivers as biogeographic islands:
Systematic Zoology, Vol. 23@, p@ 165-188.

Smith, L. D., 1968, Notes on the distribution, relative abundance
and growth of juvenile anadromous fish in the Altamaha River
system, Georgia, with special refer-ence to striped bass,
Roccus saxitilus (Walbauml/- At-lanta, Georgia'Game and Fish
Com"mission, Contribution Series no. 1.

Wharton, C. N., 1970, The souther river swamp: a multiple-use
environment: Atlanta, Gi@orgia State University, 48 p.

Willeke, G. E., et al., 1973, Georgia's water problems and related
research ne'@ids: Atlanta, Georgia Institute of Technology,
Environmental Resources Center, ERC-1173.

136

CHAPTER 5

a Summary of
Ground Water Conditions
Coastal Georgia

David E. Swanson
Earth and 'dater Division
Department of Natural Resources

Introduction

The coastal. area of Georgia for many years has been studied

by scientists interested in water resources. Probably the principle

reason for this interest is the fact thELt the water of this region

is so bountiful; it is also very complex. This is particularly

true of ground water. In recent years, numerous studies -have beer,

devoted to problems which have developed as a result of the large

ground water withdrawals by V-ELriOUS industries along the coast.

The reports which have resulted from the various studies

are listed in the last section of this report. In general, they

are technical reports written for geologists or engineers. This

report is an attempt to synthesize and generalize these previous
137

reports so that a person not trained in geology might better

understand a very complex subject. No original data was col-

lected for this report.

Basic Concepts

If we examine a section of rock such as that shown in Figure

5-1, we see, that, near the land surface, the earth consists of

a mixture of air, rock material and water. This is the zone of

aeration. As deeper portions of the rock are examined, we find

that gradually the water content increases. Eventually, the

mixture no longer contains air but rather the rock material is

4 -_ ground surface- +
soil water
zone
0
interm iatd pellicular
zone and
gravitational water

capillary capillary water
zone
water table

ground water

Figure 5-1. Distribution of water in a section of earth.

138

completely saturated with water. The transition line bC'tween the

zone of aeration and the zone of water saturation is called the

water table. All water below the water table is called ground

water. The water above the Water-table may be called soil water.

The water table, as you might suspect, is in reality a

gradational zone. Normally, the water table is a gently undu-

lating surface which is often higher beneath hills and lower

beneath valleys. During the periods of little rainfall, the

water table falls with the greatest variation in the water table

elevation beneath hills.

If we would follow the path of a rain drop as it infil-

trates the earth, we would find that it might follow a number

of different paths. One of the most important paths allows the

water to migrate vertically (f.ownward through the zone of aeration

under the influence of gravity. Eventually, the, water droplet

encounters the water table and becomes part of the ground water.

The path that it now takes depends upon the point where the ground

Water is. discharging. A simple example is shown in Figure 5-2.

Notice that the ground water flows in large arcuate paths. If

the point of discharge is distant, the paths will likely be less

arcuate. A ground water discharge area can be any surface water

body. A water well is also considered to be a ground water

discharge point.

An aquifer is a subsurface material which has sufficient

porosity arid permeability such that it will yield ground water

unsaturated zone
7, river, lake, or
swamp tole ground water

L
Figure 5-2.Generalized ground water flow in a water table aouifer.

to a water well. The ground water conditions described in the

preceding paragraphs would apply to a water table aquifer.

Under normal conditions a water table aquifer is an aquifer

which is immediately overlain by a zone of aeration. The

water level in a well penetrating a water table aquifer usually

will not rise above the top of the aquifer.

Artesian aquifers are aquifers which contain water which

is under pressure. The requirements of an artesian aquifer

system are that the aquifer be inclined and that it be overlain

by a bed of material which has a low permeability such as clay.

As shown in F-4gure5-3,water which enters such an aquifer has

d]'-fficulty escaping through the upper confining -material and

------------ --land Sur%
e

original
piezometric surface
------- -sea level
silt and clay
__%,arte ocean
Sian I
aquifer ------- - -
water) -, /I
saft water
clay, and marl
salt-water
front

Figure 5-3. General ground water flow in an artesian aquifer.

thus becomes trapped. The amount of pressure which such an

aquifer dL-velops depends upon the altitude of the aquifer where

it receives water, the permeability of the confining bed, the

amount of inclination of the aquifer and the permeability of

the aquifer. Since the water is under pressure, the water level

in a well drilled into the ac.uifer will rise above the top of

the aquifer. Occasionally there may be sufficient pressure to

cause the water level to rise above land surface thus resulting

in flowing wells. Not all artesian wells are flowing wells,

however. The correlative of the water table for artesian

aquifers is the potentiometric level, although potentiometric

level is sometimes used to refer to a water table also. The

potentiometric level is the 'Level to which water will rise in

a water well when the well is not pumped. Maps which depict the

potentiometric surface of an artesian aquifer generally show less

local "relief" than a map of a water table surface.

As water wells withdraw water they produce a cone of
141

depression. A typical cone is illustrated in Figure 5-.4. The

size and shape of a cone of depression is dependent upon such

factors as the permeability of the aquifer, whether the aquifer

is artesian or water table, recharge and discharge factors,

and the amount of pumpage. A cone grows in size rapidly at

first but enlarges at a decreasing rate as pumpage continues.

When the amount of water flowing toward the well from all

directions equals the amount of water withdrawn, the cone

stabilizes. If the cone does not stabilize, then ground water

mining is taking place. In other words, m ore water is being

withdrawn than the aquifer can continuously provide. Ground

water mining has not been identified anywhere in southern

Georgia.

It is important to recognize the fact that a cone of

depression is a necessary and unavoidable aspect of ground

water pumpage. Another important concept is that pumpage in

an artesian aquifer results in a cone of depression that might

better be termed a "cone of pressure relief.,, Rather than

actually dewatering an aquifer as in a water table aquifer,

pumpage initially reduces pressure in an artesian aquifer.

The reduction of pressure is transmitted very rapidly over a

large distance. A cone of depression in a water table aquifer

generally grows slowly and affects a small area.

Aquifers in Coastal Georgia

The coastal plain of Georgia covers approximately the

142

E)ry or t)nsatVrOted soil

A Lk

Li
One.

Figure 5-4. Effect on local water table ofpump-,ng
well (1,eopold and Langbein5
a

A 0%

southern two-thirds of the State. The sediments-found in this

province were deposited as a result of numerous invasions of

ancient seas. The millions of years of sediment deposition

resulted in a considerable thickness of sand, clay,, limestone

and marl. From examination of these sediments in a small area,

it would seem that the various.beds are-'horizontal,, but in fact,
the strata are inclined slightly. With local variations the

strata become thicker and deeper southward or southeastward from

the fall-line. At Brunswick, for example, the sediment at

5000 feet below the surface is the same age as the sediment

at Macon. Figure 5-5 is a cross-section showing this concept.

Notice that in Figure 5-5, the strata looks somewhat like

wedges. The portion of each wedge which is near tl-..e land

surface and not covered by a younger wedge forms that stratum's

outcrop. Some strata naturally do not have an outcrop but

rather they can only be found by drilling. Ground water in a

permeable stratum can most easily be recharged by precipitation

falling upon the stratum's outcrop area. Recharge will also occur

in other ways which will be described later.

Aquifers

In the coastal area under consideration there are two

known aquifers and one potential aquifer which has not been

adequately explored, The oldest rock unit which may potentially

be an aquifer in the northern coastal area is the Tuscaloosa

144

N W S E
Macon Brunswick

Y X

x )r

Y
Y

Figure 5-5. Idealized cross section from Macon to BrunsWick.,

Formation. Several test wells have penetrated the Tuscaloosa

Formation in the Savannah area but the goal of these wells was

not to determine the water beai,:@ing characteristics of this

unit. Since the formation consists of sand, one would antici-

pate that a reasonable quantity of water could be withdrawn

145

from it. At Savannah, however, the formation is found at

depths below 2500 feet and will probably contain water

having quality problems. Because of its depth the temperature

of the water would be higher than normal which might make it

useful to catfish farmers.

The youngest aquifer consists of sand and gravel. In

general this aquifer is thickest and thus has its greatest

potential near the coast. The permeable nature of this

aquifer is demonstrated by the stream pattern along the coast.

Except for the large rivers which originate outsi4e the region

there are few small streams. In other words, most of the preci-

pitation which falls on coastal Georgia immediately infiltrates

the surface and recharges this shallow, young aquifer.

The shallow aquifer is used by a few people for domestic

purposes and by a few industries for supplemental water. Where

the aquifer is thick and composed of coarse material, large

quantities of water could be withdrawn. The areal extent of

this aquifer is shown in Figure 5-6.

The major aquifer is a thick sequence of limestones which

lies between but separated from the two aquifers described

above. The limestone is commonly composed almost entirely of

of the shells of sea critters. It is honeycombed with numerous

small passageways and occasionally has large cavernous zones.

The permeability of this rock is very high.

The major limestone aquifer is locally known as the
principal artesian aquifer. As shown in Figure 5-7athis aquifer

E M A N U E Lz--
LAURENS
TREUTLEN CANDLER GULLO C .4 @EFFINGHAM
cc

-WHEELER EVANS
TOOMBS
TATTNA-LL- CHA-THA
T-E LFA I KL .101,
JEFF LIBERTY
-L DAVIS, APPLING L 0 N 0

Al, C 0 F F E E BACON W Y.N E
MC I N.TOSH
f

I ERCE
ATKINSON 7
R BRAN TLE N
NIER. 8 7RA @tT L E

CHARLT N
.E C H 0 .L

Figure 5-6 Aerial extent of the potential shallow sand
and gravel aquifer.

is a usable aquifer throughout much of the coastal plain. Its

upper surface is difficult to accurately contour due to the

fact that recent and ancient solution of the limestone has

created a very rough surface. Figure 5-7b shows the depth to

which one must drill before encountering the top of this

aquifer. The artesian characteristics of the aquifer are due
to the aquifer's gentle dip -toward the sea and 'its covering of

clayey material.

147

SCREVEN
N, S 0

EMANUEL

N BULLO
L A U TREUTLEN CANDLER FFINGHAM

Uj
EVANS
A 0 0 LY
D 0 D G E WHE ER OMBS CHA$ AM
E R 0 TATTNALL-
I\W, L
C R IS OX TELF L I a ERTY
LO G
J FF I_q
a E N
TERRELL __.@,IN ,LL APPLING
.(AN'DOLPH L E E URNER H DAVI

N E,
RTH R W I N BACO W me iN.T.OSH
CLAY 1, DOUGHERTY C 0 F F E E
CAL N
TI FT
P I E R C E
L Y B A*K E R
BERRIEN ATKINSON
17 G N
W A R E NTL
f'MITCeHEL COLQUtTT-/@
ER @-tOOK

"LAN[ R
r
-1T,FMiNOL IE C L I h C K C A ?A D E
RA cHA '-TOM
DECATUR HOMAS LOWNDE
B :R
E C H 0 L

F 1. A.

Figure S-7a. Areal extent of the principal artesian aquifer
and direction of ground water movement.

148

82* 81.

0
SOIJ

Q,
I
a--

SAVANN H

32" + 32*

-3

icebor

Jesu
0

-450-

-600

B:?UNSWICK

31-

E X P L A N A T 1 0 N

-450---
Structure contour
St. Marys Shows altitude of the top of the principal
artesian aquifer. Dashed where opproxi motel y
I \Vs located. Contour interval 50 feet; datum is
Fernandina
Beach mean sea level.
GEORGIA
FLORIDA@ Q0

fp'e'

82'
0 5 10 ?5 20 25 MILES Geology by R. E Kra--- and 0 0 Gregg, (97;

Figure 5-7b. Depth to the top of the principal artesian
aquifer in coastal Georgia (Krause and
Gregg, 1972).

149

Principal Artesian Aquifer Recharge and Discharge

As stated earlier a large quantity of water can enter a
permeable stratum where that stratum is exposed to the surface.

A large quantity of water also enters the principal artesian

aquifer even where the aquifer is covered with a clay confining

bed. In places, water enters the aquifer from strata lying

below the aquifer. Such a transferof water is due to the fact

that water moves from areas of high pressure to areas of low

pressure. If the water table, for example, is at-an elevation

which is higher than the potentiometric level of the principal

artesian aquifer, then there is a tendency for water to move

downward and into the principal artesian aquifer. In Figure 5-8,

water is recharging the aquifer from above at "B" because the

A B I

Water Level of
De Aqutfer Water Leve.1 Artesian Aquifer
.:!@eep

C? Water
'De Table
1P

e-t

Figure 5-8. Recharge to an artesian aquifer.

water table is higher than the artesian aquifers potentiometric

level. Of course, the opposite situation is true also as shown

to the right of "B". The deep artesian aquifer in Figure 5-8 is

a higher pressure than the shallow artesian aquifer and thus is

constantly discharging water. A clay confining bed tends to

inhibit such a transfer since the clay has-a low permeability.

However, when dealing with very large areas such as in south

Georgia, the total quantity of water that is able to seep through

a clay layer is very large.

Since water in an aquifer tends to move from areas of high

pressure to areas of low pressure, a map showing the potentio-

metric surface of an aquifer can be used to determine the direc-

tion of ground water movement (as in Figure 5-7a). Maps con-

structed in past years can be used to identify changes that have

taken place in the aquifer. The type of change noticed can be

attributed to natural effects or man-made effects. Krause and

Gregg (1972) illustrated the changes which have taken place in

the water levels along the coast. These illustrations are

reproduced as Figure 5-9aand5-9b. Notice that the 1971 map depicts

the large cones of depressions which are a result of ground water

pumpage.

The natural discharge arEia of the principal artesian

aquifer in eastern Georgia was originally the estuaries in

South Carolina and the submarine outcrops of the aquifer off

the coast of Georgia and Florida. Most of the water seems to

have discharged to the shore area of South Carolina as

151

02' 81,

O(J
A/

... ..... .. .. .

...... . .. ..

..... . ...

.. ... . ..

..........
A.

. .......
. . ....... . . ....

. ...... . ...

.........*

................

EXPLANATION

. . . . ... . . .

Area where flow from artesian wells could
atys have been obtained.

-50-
Fernandina
Beach Water-levei contour
GEORGIA
Shows altitude of artesian water level.
FLOR16@ Contour interval 10 feet; datum is mean
sea level.

82' 81,
0 5 10 15 20 25MILES Hydrology from MA.Worren, 1944

1880
01

Figure 5-9a. Water level in the principal artesian
aquifer, 1880 (Krause and Gregg, 1972).

152

82'

0X,

-20

A A NAH

+ 32*

@0
Riceboro
0

Je
60

. . . .. . . . . . .

....... .
.t . ... . . . . . . .@`.

......... ... ... .. .

........ .. .. . . .. . . .... ..

.--40

+ + 31*

EXPLANATION

-40
%. . . . . . . . . . . . . . . . . . . . ..... Area where flow from artesian wells could
. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .-30 have been obtained.
70, -50---
11 Fernandina Woter-level contour
Beach Shows altitude of artesian ter level.
p r
GEORGIA Dashed where a proximatewlyo lo a led.
FLOMDA@ Conlour interval 10 feet, 20.feet below
-20-fool contour; datum is mean sea level.
VMS 'P. 40
0 Estimated pumpage, in million gallons per
day at major pumping sites.

82*
to 15 20 25 MILES Hydrology by A E Klou@, 19TZ
L Werfor-hrrel contour$ by E A Z-m-n ono 0 8 Odun,, 1972
1971
Figure 5-9b. Water level in the principal artesian aquifer,
1971 (Krause and Gregg, 1972).

153

indicated on the 1880 map in Figure 5-9a. It is difficult to

determine where the present natural discharge area is, if indeed

it does exist.

Water Use In Coastal Georgia

Background

There are several reasons why ground water use in the

coastal area is presently so high. Before the present large-

scale development,flowing wells were an important asset. The

original potentiometric level was high enough to cause wells to

flow thirty to seventy feet above the land surface. Numerous

mills used this natural power to operate water wheels which in

turn operated grinding wheels and saw. Naturally, as such use

expanded, the original pressures decreased thus making the use

of pumping equipment necessary.

The cost of treating a water supply is a critical factor

for most uses. Most industries require water that will meet

certain quality restrictions. The same is also true of munici-

pal and agricultural users. Surface water in the coastal area

requires expensive treatment to adjust its chemical and sediment

characteristics before it can be used. Ground water, on the

otherhand, is pure enough for almost any use. The only quality

restriction is the natural hardness of the water and occasionally

a high sulfate content. Municipalities are required to chlorin-

ate the water before distribution even though the ground water

does not naturally contain bacteria.

The cost of a ground water supply as compared to a surface

154

water supply in coastal Georgia is enhanced because of the very

'Large quantities of water that can be pumped from a single well.

This allows an engineer to select a plant location based upon

factors other than proximity to a river or reservoir. In the

Brunswick area, for example, the nearest usable surface water

body is a considerable distance from the City. Ground water,

on the other hand is of bette::, quality and can be obtained

within the confines of a plan-_-Is property. In one instance,.a

withdrawal of 11,000 gallons of water per minute was registered

from a very small area.

Accurate comparative costs o� surface versus ground water

have not been developed. Ground water is probably costing users

several cents per thousand gallons whereas surface water proba-

bly costs at least ten cents Fer thousand gallons. A plant

which requires 100 million gallons of water per day is obviously

going to examine its water cost very closely when selecting a

plant site.

Recent Water Use

The importance of ground water to the economy of the

coastal area is dramatically illustrated in a recent report

"Use of Water in Georgia, 1970, with Projections to 199011

(Carter and Johnson, 1974). Tables 5-1 and 5-2 of that report

are reproduced here. Notice that the Coastal Area Planning

and Development Commission region withdraw more ground water

for public supply, industrial use and thermoelectric plants

than any other area in the State.

155

Table 5-1 - Withdrawal use of water (million gallons per day) by Area Planning
and Development Commission region, source, and principal use, 1970.
Un

-1?1,j,,i..rg And Rural Us--3
Public Supply Self-Supplied Thermoelectric Total
Ojorncstic Liv ock Irrigation Industry Power Plants
Co,T.7:-.-,-.,;ion Groun Surfacu Ground Ground Surface Ground Su rface Ground Surface Ground Surface Ground Surface Total
Regions V41 Water Water Water Water Water Water Water Water Water Water V,ater Water
tcr

A;tamaha-Gcor,j;,i @;ou-.@%trn 10.71 0 3.03 0.81 0.80 0.98 2.35 66.53 0 0 0 82.16 3.15 85.31

Atlanta Region 1.97 192.44 5.48 .22 .47 0 .03 .47 .95 0 601.40 8.14 795.29 803.43
i
Central Savannah River 6.66 23.25 4.48 .51 1.32 .32 .22 16.31 71.87 0 0 28.28 96.66 124.94

Chattahoochcp-Flint 1.85 12.71 2.96 .18 .55 0 .01 .54 4.41 0 657.00 5.53 674.68 680.21

coastal 38.71 35.00 4.59 .20 .26 .10 .11 255.46 188.75 4.38 513.06 303.44 737.18 1,040.62

Coastal Plain 14.24 0 2.65 .71 1.02 2.60 10.80 19.36 6.80 0 0 39.56 18.62 58.18

Coosa Valley 18.85 19.17 5.67 .50 .97 0 .05 13.20 65.73 0 54930 30.22 635.62 665.84

Georgia MoUntains 2.10 16.71 4.76 1.45 '89 0 .25 2.35 1.07 0 0 10.66 18.92 29.58

Heart of Georgia 7.38 0 2.16 .61 .74 .85 .66 1.47 5.91 0 0 12.47 7.31 19.78

Lower Chattahoochee 2.37 31.95 1.34 .14 .41 .09 .15 0 1.95 0 0 3.94 34.46 38-40

Vclntosli Trail 2.30 11.61 3.08 .15 .64 0 .12 .52 5.12 0 0 6.05 17.49 23.54

Middle Flint 5.40 0 1.97 .34 .86 .83 1.98 1.05 0 0 0 9.59 2.86 12,45

Middle Geogia 12.30 21.76 1.86 .12 .47 .02 .08 20.52 26.14 0 241.80 34.82 290.25 325.07

Northeast Georgia 1.50 17.50 3.77 .67 .93 0 .15 1.39 2.72 0 0 7.33 21.30 28.63
North Georgia .63 16.69 2.98 .48 .43 0 .01 .47 7.13 0 0 4.56 24.26 28.82
Oconee 2.27 7.64 1.70 .21 *57 32.92 4.64 0 1,139.60 37.12 1,152.49 1,189.61

Slash Pine 6.70 0 2.32 .64 .51 .38 3.27 .42 .07 0 0 10.46 3.85 14.31
Southwest Georgia 29.79 0 4.67 1.20 2.54 3.20 9.89 17.17 88.48 0 237.50 55.98 338.41 - 394.39
Total by Source 40C.43 59.47 9.14 14.40 9.39 30.17 450.20-1 481.74 4.38 3,940.06 690.31 4,872-80
Total by Subcategory 59.47 23. 54 39.56 5,563.11

Total by Category 564.16 122.57 931.94 3,944-44

Fkea Planning Population Eorvcd Average Walcr Ute (MiM) For capita
Prid 00volopment By By Co!,nF,,-5rcial L:,s,2 iGPD)
Commission Groun Surface Total Cr-@-.,iid Surface And
Water Water V'J'atar Water Residential Industrial Total Residential Total

Altamaha-Georg:a Sou-nern 59,300 0 59,300 10.71 0 5.84 4.87 10.71 98 181

Atlanta Region 29,050 1,298,650 1,327,700 1.97 192.44 111.78 8Z63 194.41 84 146

Central Savannah River 64,650 146,800 211,450 6.66 23.25 18.10 11.81 29.91 86 141

Chattahoochee-Fl:nt 11,000 76,600 87,600 1.85 12.71 7.72 6.84 14.56 88 166

Coastal 205,600 0 205,600 38.71 35.00 19.90 53.81 73.71 97 359

Coastal Plain 103,900 0 103,900 14.24 0 7.48 6.76 14.24 72 137

Coosa Valley 189,200 10.85 19.17 16.06 13.96 30.02 85 159
1 56,800 132,400

Georgia Mourtains 14,900 82,500 97,40C. 2.10 16.71 11.09 7.72 18.81 114 193

Heort of Georgia 58,550 0 58,550 7.38 0 5.16 2.22 7.38 88 126

1 0 205,600 2.37 31.95 23.51 1C).81 34.32 114 67
ower Chattahoochee 1 17,600 188,00
Miclntosh Trail 12,650 78,850 91,500 2.30 11.6i 7.30 6.61 13.91 80 152

Middls Flint 47,500 0 47,500 5.40 0 2.95 2.45 5.40 62 114

Middle Gecrg;a 77,100 145,200 222,300 12.30 21.76 20.94 13.12 34.06 94 153

Northeast Georgia 9,300 101 110,650 1.50 17.50 10.64 8.36 19.00 96 172

North Georgia 7,700 63, 1 70,850 .63 16.69 6.32 11.00 17.32 89 244

Oconee 17,350 40,650 58,000 2.27 7.64 3.96 5.95 9.91 68 171

Slash Pine 49,450 0 49,450 6.70 0 4.15 2.55 6.70 84 135
Southwest Georgia 192,600 0 1 192,600 29.79 0 15.34 14.45 29.79 80 155

2,354,159 Y,7.73 406.43 298.24 265. 66
State coo 3,389,150 92 564.16 118 1

N*4

Trends in future water use are very difficult to predict.

It is safe to say that ground water will always be the primary

source of high quality water in the coastal area but at present,

it is desirable to locate new water using industries away from

the major pumping centers if possible. Throughout the area
shown in Figure 5-7a the principal artesian aquifer can supply
large quantities of very high quality water. Many other aquifers

are capable of a much larger use also.

Stress to the Aquifer

Natural Stresses

Probably the greatest stress to the ground water supply

which nature causes is the minor variations in annual precipita-

tion. Water levels in aquifers respond to variation in precipi-

tation in a manner which depends a great deal upon the physical

characteristics of the individual aquifer. Aquifers which are

under water table conditions generally have a dramatic and

quick response to precipitation variations. The-artesian

aquifer response is most often difficult to detect. Water

table variations can be correlated to specific rainfall events

whereas artesian potentiometric levels may be correlated with

precipitation variations that range over several years.

Artesian water levels respond quickly to changes in

pressure. Such natural changes in pressure are caused by such
things as earthquakes, tides, and the wind. Trains and explo-
sions can also affect artesian water levels. Generally, such

changes do not disturb the long-term water levels. An

158

interesting discussion of these effects can be found in "Ground

Water Designs and Patterns" by J. W. Stewart (1971).

Man-made Stresses

It is a generally accepted fact that man has strained the

aquifer system in the coastal area to a much larger degree than

nature has. The 1971 water level map shown in Figure 5-9b

identifies the "points" where the system is being strained the

greatest. The greatest cone of depression is centered at an

industrial park near Savannah. St. Marys, Brunswick, Jesup,

and Riceboro have cones which are smaller. Notice that in 1971

the cone of depression near Brunswick is smaller than the cone

at Savannah even though more viater was being withdrawn at

Brunswick. This is due to the greater transmissivity (a

measure of the water yielding characteristics of an aquifer)

at Brunswick than at Savannah.

The 1971 water level map illustrates that the principal

artesian aquifer must be managed as a unit since pumpage in one

area ultimately affects a very large portion of the aquifer.

Interstate cooperation will be needed for management purposes

in the near future..

The large cone of depression at Savannah has not resulted

in dewatering of the aquifer there. Since this is an artesian

aquifer, we are looking at a cone of "pressure relief." Before

dewatering of the aquifer and concurrent transition from

artesian to water table conditions takes place, the water levels

would have to decline another 10 to 20 feet. This is shown

159

diagrammatically in Fig. 5-1.0. Similarly, dewatering is not

taking place anywhere within the coastal area.

Original Potentiozaetric Level

Confining Unit

Figure 5-10. Cone of" depression in an artesian a:quifer.

Effects'of the Stress

As mentioned earlier in this report, ground water moves

from areas of high Pressure to areas of low pressure. This

results in a potentially undesirable situation when a higher

pressure zone contains water of poor quality and a nearby low
pressure zone contains water of good quality. Two problem areas have

been documented in coastal Georgia where water of poor quality

is presently moving toward pumping centers,
0

The problem area which has received the most attention in

-recent years is at Brunswick. The brackish water

160

encroachment can best be explained by the use of Figure 5-11.
In very general terms, there are four geologic strata. Confin-

ing unit number 1 is found between the depths of 150 feet and

300 feet. This unit is impermeable and creates the artesian

conditions. The principal artesian aquifer is found below the

confining unit with the best water yielding zones between the
depths of 600 feet and 1050 feet. This is the zone from which

var-Lous users in Brunswick withdraw over 100 million gallons

per day (MGD). Confining unit number 2 is found between leoo
feet and 1050 feet. In places, however, this confining

I W center of S E
Pumpage
150
Confinin*
Unit #1
300

600

Principal
Artesian
Aquifer

1000 -Lf. Unit #2
1050 Brackish
Water
Zone

1 0

Figure 5-11. Diagram o--" the Brunsw.-..ck intrusion problem.
161

unit has been breached. The reasons for these ineffective
zones in the confining unit are not clearly under-

stood. The lowest stratum of concern occupies the interval from

1050 feet to 1300 feet. It is this stratum that provides water

that contains chlorides in concentrations of up to 4500 milligrams

per liter. This lowest zone now has a potentiometric level

which is greater than the potentiometric level of the principal

artesian aquifer because of the water withdrawn from the

artesian aquifer. The ineffective zones in confining unit

number 2 allow brackish water from the lowest stratum to move

upward and thus into the fresh water of the principal artesian

aquifer. The brackish water then moves with the native water

toward the center of pumpage.

Pumpage at Savannah has created a situation which is common

to many coastal cities. Referring to Figure-5-12 we can see that

S W N E

P-4
Savannah W 0
:j ;ON
6010 0 10
0 94
.0
H 0 0
0 En $4
0
Le A4

Sea Level

Confining Unit

Brackish
Principal Xrtesjoa Water

confining Unit

Figure 5-12. Diagram of the salt water intrusion probleff
162 at Savannah.

we have basically two subsurface strata of concern. Confining

unit number 1 is the unit which results in the artesian condi-

tions at Savannah. It is the same age as the confining unit at

Brunswick. Notice how this unit becomes shallower toward the

northeast and is breachqd by the estuaries. Below the confining

unit we find the principal artesian aquifer. Again this is the

same aquifer which is found in Brunswick. The deeper portions

of the principal artesian aquifer north and east of Savannah,

contain water which is brackish.

Before large ground water withdrawals in Savannah, the

potentiometric level was higher than sea-level. Thus, where

the principal artesian aquifer is directly exposed to the

estuaries, the original water pressure in the aquifer was high

enough to keep the denser sea water out of the aquifer. The

ground water was actually discharging fresh water to the

estuaries. As pumpage increased, the potentiometric levels

naturally declined. At present, the potentiometric level is

lower than sea level and salt water is slowly recharging the

aquifer as shown in Figure 5-12.

Brackish water in the lower portions of the aquifer is

likely to be moving toward the pumping center also. Due to the

fact that this brackish water is naturally nearer to Savannah,

it may move more rapidly tOWELrd the pumping center.

Both problem areas discussed above will most likely become

worse with time due to the fact that nothing is presently being

done to stop the intrusions. If pumpage should increase, the

163

problem will obviously also increase. An increase in pumpage

will increase the quantity of brackish water moving toward the

pumping center and increase its rate of movement.

As the brackish water approaches the cone of depression,

the pressure gradient which is causing the brackish water to

move increases. This increase in the pressure gradient causes

the brackish water to move at an accelerating rate. As Figure 5-13
illustrates, the velocity is low at distances far away from

the center of the cone but increases rapidly as this distance

decreases. An increase in pumpage would result in the graph in

Figure 13 being shifted upward of toward the left (with an obvious

TV
0 1.-,
.G

0 L--
0 distance increasing
Figure 5-13.Rate of ground water movement toward a
cone of depression.
164

upward limit as to the maximum velocity).

Solutions to the Problems

A number of solutions have been offered that may solve the

two intrusion problems. Each solution involves a redistribution

of pressure within the aquifer system and thus is extremely

expensive.' The proposed solutions are briefly generalized below.

A. Reduce the quantity of water withdrawn from the princi-

pal artesian aquifer at each pumping center. Additional

water needs would have to be met by:

1. Using wells located far from the pumping center.

2. By using surface water, or

3. By using alternate (deeper or shallower) aquifers

where they exist.

B. Attempt to reestablish a higher potentiometric level in

the aquifer as compared to the brackish water zone

without reducing existing pumpage.

1. Install wells tc inject fresh water into the

principal artesian aquifer between the pumpage

center and the Eource of the brackish water

intrusion.

2. Install pumping wells (relief wells) in the brackish

water zones to lower the pressure in these zones in

relation to the principal artesian aquifer. (This

method would not apply to the shallow encroachment

experienced at Savannah).

C. intercept the brackish water before it can reach a

165

pumping center.

1. Similar to B-2 except the wells would withdraw

water from the principal artesian aquifer between

the pumping center and the zone of brackish water

intrusion. The brackish water would move from its

point of origin to the interceptor wells and then

be withdrawn.

Two primary problems exist with any of the above proposed

solutions. First of all, none of the solutions have been tested

for conditions unique to the coastal area. Therefore -there is

no adequate way of accurately determining the cost-benefit

ratio of any of the alternatives listed. In fact, there is no

guarantee that some of the solutions would even make a signifi-

cant enough impact on the intrusion problems. Secondly, the

aquifer is extremely permeable. The quantity of water that

would have to be withdrawn, injected or the amount of pumpage

that would have to be reduced to make an impa(---'L-- would be

staggering.

The solutions which involve the withdrawal of water (B-2 and

C-1) may offer advantages in that the water withdrawn may be

used for some industrial or recreational purposes.

Summary

An attempt has been made to explain the ground water

resources of the coastal area in very general terms. It would

be easy to "write a book" on any one particular aspect of the

subject--in fact, this has been done for many subjects as

166

illustrated in the next section. The interested reader can

expand from this list to subject matter related to general

ground water concepts and not to Georgia specifically. Up-to-

date information on the aquifer system is available in unpub-

lished form from both the U. S. Geological Survey and the Earth

and Water Division, Department of Natural Resources.

Past studies of ground water in the coastal area have

resulted in a fine data base which has allowed parts of the

system to be modeled by digital computer. Each past study was

completed for a relatively low cost since much of the work

involved basic data collection and interpretation. If future

studies of the principal artesian aquifer are to be significant

studies the costs will be much greater than experienced in the

past. This is because of the current need for test wells,

computer programming time and more sophisticated tests of

model results.

Both the State and federal geological surveys will con-

tinue to collect data in this area and study alternate water.

sources. The future course of action at this point is up to

the water managers.

167

SELECTED BIBLIOGRAPHY

All of the following reports are available for examination at
the main office of the Earth and Water Division, Georgia Department
of Natural Resources. Reports published by this agency (and the
old Department of Mines) can be purchased for under three dollars.

Callahan, J. T., 1959, Jekyll Island - its geology and water
resources: Georgia Mineral Newsletter, Vol. XII, no.-2,
p. 33-39. (Fall).

----- 1960, Wild-flowing, wells waste water: Georgia Mineral
Newsletter, Vol. XIII, no. 1, p. 21-23 (Spring).

----- 1964, The yield of sedimentary aquifers of the Coastal
Plain, Southeast River Basins: U.S. Geol. Survey Water-
Supply Paper 1669 W, 56 p., 1 pl., 11 fig., 6 tables.

Carter, R. F., and Johnson, A. M. F., 1974, Use of water in
Georgia, 1970, with projections to 1990: Georgia Water,

Resources Survey, Hydrologic Report 2, 74 p., 9 fig.,
7 tables.

Carver, R. E., 1968, The peizometric surface of the Coastal
Plains aquifer in Georgia, estimates of original elevation
and long-term decline: Southeastern Geology, Vol. 9,
no. 2, p. 87-99.

Counts, H. B., 1958, The quality of ground water in the Hilton
Head Island area, Beaufort County, South Carolina: Georgia
Mineral Newsletter, Vol. XI, no. 2, p. 50-51. (Summer).

----- 1960, Salt water encroachment into the principal artesian
aquifer in the Savannah area, Georgia and South Carolina:
Am. Water Works Assoc. Jour., Southeastern Sec., Vol. 24,
no. 1, p. 25-50.

Counts, H. B.,and Donsky, E., 1959, Salt water encroachment,
geology, and ground water resources of Savannah area,
Georgia and South Carolina - A summary: Georgia Mineral
Newsletter, Vol. XII, no. 3. p. 96-102. (Winter).

----- 1963, Salt water encroachment, geology, and ground-water
resources of Savannah area, Georgia and South Carolina:
U. S. Geol. Survey Water Supply Paper 1611, 100 p., 6 pl.,
9 fig., 8 tables.

168

Davis, G. H., Small, J. B., and Counts, H. B., 1963, Subsidence
related to decline of artesian pressure in the Ocala
Limestone at Savannah Georgia: Geol. Soc. America, Eng.
Geology Case Histories, no. 4, p. 1-8.

Dyar, T. R., Trasker, G. D., Wail, R. L., and others, 1972,
Hydrology of the Riceboro area, coastal Georgia: U. S.
Geol. Survey, (misc. re-port published by Ga. Water Quality
Control Board). 74 p.

Furlow, J. W., 1969, Straitigraphic and economic geology of the
eastern Chatham County phosphate deposit: Georgia Geol.
Survey Bull. 82, 49 p., 7 fig., 2 maps.

Gregg, D. 0., 1966, An analysis of ground water fluctuations
caused by ocean tides in Glynn County, Georgia: Ground
Water, Vol. 4, no. 3, p. 24-32, 6 fig.@ 1 table.

Gregg, D. 0., and Zimmerman, E. A., 1974, Geologic and hydrologic
control of chloride contamination in aquifers at Brunswick,
Glynn County, Georgia: U. S. Geol. Survey Water Supply
Paper 2029-D, 44 p., 10 fig., 6 pl., 8 tables.

Herrick,.S. M., 1965, Subsurface study of Pleistocene deposits
in coastal Georgia: Georgia Geol. Survey Inf. Circ. 31,
8 p., 2 fig.

Herrick, S. M., and Vorhis, R. C., 1963, Subsurface geology
of the Georgia Coastal Plain: Georgia Geol. Survey
Inf. Circ. 25, 78 p., 28 fig., 12 tables.

Krause, R. E., 1972, Effects of ground water pumping in parts
of Liberty and McIntosh Counties, Georgia,-1966-70:
Georgia Geol. Survey Inf. Circ. 45, 1 5 p., 7 fig., 2 tables,

Krause, R. E.,-and Gregg, D. 0., 1972, Water from the principal
artesian aquifer in coastal Georgia: Georgia Water
Resources Survey Hydrologic Atlas 1, 1 p., 15 fig., 1 table,

Leopold, L. B., and Langbein, W. B., 1960, A primer on water:
U. S. Geol. Survey, Washington, D. C., 50 p., 16 fig..

McCollum, M. J., and Counts, H. B., 1964, Relation of salt
water encroachment to the major aquifer zones, Savannal;
area, Georgia and South Carolina: U. S. Geol. Survey
Water Supply Paper 1613-D, 26 p., 4 pl., 6 fig.5 1 table.

Odom, 0. B., 1961, Effects of tides, ships, trains, and changes
in atmospheric pressure on artesian water levels in wells
in the Savannah area, Georgia: Georgia Mineral Newsletter,
Vol. XIV, no. 1, p. 28-29. (Spring).

169

Stewart, J. W., 1960, Relation of salty ground water to fresh
artesian water in the Brunswick area, Glynn County, Georgia:
Ga. Geol. Survey Inf. Circ. 20, 42 p., 6 fig.5 2 tables.

----- 1971, Ground water designs and patterns: Georgia Geol.
Survey Geologic Report 1. 21 p.

Stewart, J. W., and Croft, M. G.5 1960, Ground water wi-.hdrawals
and decline of artesian pressures in the coastal counties
of Georgia: Georgia Mineral Newsletter, Vol. XIII, no. 2.
p. 84-93. (Summer).

Stringfield, V. T., 1966, Artesian water in Tertiary limestone
in the southeastern states: U. S. Geol. Surv. Prof. Paper
517, 276 p., 47 fig.5 5 tables.

Wait,, R. L., 1962, Interim report on test drillings and water
sampling in the Brunswick area, Glynn County, Georgia:
Ga. Geol. Survey, Inf. Circ. 23, 46 p.5 13 fig., 3 tables.

----- 1965, Geology and occurrence of fresh and brackish ground
water in Glynn County, Georgia: U. S. Geol. Survey
Water-Supply Paper 1613-E,94 p.5 4 pl.5 29 fig.,,15 tables.

Wait, R. L., and Callahan, J. T., 1965, Relations of fresh and
salty ground water along the southeastern U. S. Atlantic
Coast: Ground Water, Vol. 3, no. 47 p. 3-17.

Wait, R. L., and Gregg,, D. 0.2 1.973, Hydrology and chloride
contamination of the principal artesian aquifer in Glynn
County, Georgia: Ga. Water Resources Survey, Hydrologic
Report 1, 93 p.5 2 pl., 38 fig.5 16 tables, 2 appendix.

Wait, R. L.,and McCollum, J. J.5 1963, Contamination of fresh
water aquifers through an unplugged oil test well in Glynn
County, Georgia: Georgia Mineral Newsletter. Vol. XVI,
no. 3 & 4 (Fall-Winter).

Warren, M. A., 1944, Artesian water in southeastern Georgia,
with special reference to -the coastal area: Ga. Geol.
Survey Bull. 49, 83 p.5 1 map.

----- 1945, Artesian water in southeastern Georgia, with special
reference to the coastal area--well records: Ga. Geol.
Survey Bull. 49-A. 83 p.5 1 map.

'170

CHAPTER 6

an Overvim
Of
Coastal Georgia Wildlife

1-Y

Jerry T. McCollum
Resource Planning Section
Office of Planning and Research
Department of Natural Resources

Other papers on coastal resource systems contained in this report
highlight the relationship of wildlife with various environmental
features. This paper provides an overview of coastal wildlife,
drawing upon available printed sources of information. This
paper should be considered a general background paper upon which
a further synthesis of wildlife information for coastal Georgia
can be based.

_Lntroduction

The wildlife community along the Georgia coast is extremely

diverse. It contains many forms which are well known and quite

spectacular, such as, the Eastern brown pelican (Pelecanus

occidentalis), the clapper rail (Rallus ion.g-Li,ostris'), and

Eastern fox squirrel (Sciurus as well as many wildlife

forms which are relatively unknown tG dnyone except research

scientists. Although these obscure forms are not well known

to the layman, they often occupy an important, if not vital,

position in the wildlife community, either as a member of a

food chain or as a converter of material required by members

of a food chain.

171

Whenever we speak of wildlife in general, the forms which

immediately come to mind are the popular and more spectacular

ones. Usually these forms have gained attention because of

their value to the sport of hunting or fishing, or because they

have been recognized by special interest groups as being endan-

gered for one reason or another. If one made the statement

that these popular forms were valuable to at least a segment of

our society, there would probably be no pointed disagreement

with the statement. However, acknowledgement of the value of

those obscure and relatively unknown wildlife forms by a society

which is industrially oriented and only beginning to become

aware of its total environment will require much effort and

much foresight in the planning and implementation of state and

federal programs. The public must be educated to the fact that

each member of a wildlife community has a functional role to

play no matter how obscure or uninteresting nature's design

has made it. Seemingly uninteresting forms may be an essential

link in the food chain of the larger popular forms, as well as

being a vital member of the wildlife community supported by a

particular ecosystem. The exact roles of many forms, within the

community, large and small, obscure and spectacular, are only

beginning to be studied and determined. Some are known and there

is considerable evidence that all of nature's wildlife species

play important roles within their community (Smith, 1974). Many

forms may be relatively unimportant for most of their life and

then, reacting to nature's cue, they become the very pulse of the

172

wildlife community (Wharton, 1974).

The role of an individual type of wildlife within d total

ecosystem is unknown in many cases. This lack of information

is a major reason for protecting wildlife, since accidental

elimination of the animals or the habitats may stimulate a

chain reaction which may have many adverse effects, or com-

pletely eliminate a type of animal. A wide variety of ecologi-

cal factors must be understood before the value of wildlife and

their habitats is understood.

Wildlife has many values associated with hunting and

fishing. Hunting is an important recreational activity in

coastal Georgia enjoyed by both residents and visitors. Many

different habitats, including marshland areas, coastal islands,

fresh water river swamps and certain forested areas away from

population centers are used for different types of hunting.

Fresh and salt water fishing for recreation and commercial

purposes is another important activity related to wildlife.

In addition to hunting and fishing, Georgia's wildlife has

scientific and educational values.

Coastal Habitats and their Animal Dependents

Habitat has been define@. as "The place where an animal

lives" (Odum, 1963), and it is generally accepted that the

h-abitat selected by a population of animals will be the one

which offers the optimum conditions which exist within the

limits of its travel. When the habitat of a population is

detrimentally modified, the population will be forced to move

173

into new areas if new areas are available. Movement of wild-

life from one region -to another places stress on the wildlife

forms already occupying the new area because habitat which is

supporting a wildlife community at its natural carrying

capacity cannot support additional animals regardless of their

type of numbers (Odum, 1963). Wildlife is absolutely dependent

upon suitable habitat and the quality of wildlife in any

habitat is directly proportional to the quality and quantity

of that habitat.

The Continental Shelf

The Continental Shelf is a relatively shallow region

immediately seaward of the bays along the coast. Along the

Georgia coast, the water varies in depth from about 60 feet

to a maximum of 168 feet (Johnson, et al., 1971); and extends

offshore a distance of 70 to 80 miles (Henry and Hoyt, 1968).

Vegetation along the bottom on -the Continental Shelf is

- harbors a diverse animal community.
sparse, yet this habitat

This wildlife community is localized around the various reefs

and the Snapper Banks. It is mainly composed of mature organisms

whose larval stages were planktonic and/or whose development

largely occurs in an estuarine habitat. Representative bottom

organisms include acorn barnacles, oysters, sea cucumbers, and

scallops. All of these animals feed on detritus which is

continually rained down from the waters above. Thi-s detritus

consists of small particles that are the dead or decomposed

174

bodies of planktonic piantsand animals. The detritus is an

essential component of the food chain of the wildlife commun-

ity of the Continental Shelf since it supports an extremely

diverse group of intermediate members of the food chain.

These intermediate members, Ln turn, support such large

species as' the rock sea bass (Centropristis-philadelphica),

the black sea bass (C. Striatus), and the sand perch

(Diplectrum formosum). In addition to these species of fish,

there are a number of birds which utilize those intermediate

members of the food chain offshore. These birds include such

species as the red-throated --oon (Gavia immer), and the ganner

(Morus bassanus.) (Johnsonet al., 1971).

The Beach and Dunes

The beaches and dunes along the Georgia coast are composed

of fine quartz sands (Greaves, 1966). Johnson, et al., 1971,

suggests that the beach and (June habitat is "characterized by

the following zones: (1) shoreline - the narrow zone seaward

from the low tide shore line permanently covered by water over

which the beach sands and gravels move with wave action. (2)

foreshore - the lower shore zone beyond the reach of ordinary

low and high water levels. (3) backshore - the upper shore

zone beyond the reach of ordinary waves and tides extending to

the base of the dunes; and (4) dunes-ridges - of windblown

(eolian) sand."

The diversity of the vegetation - other than aqua-tic - of

this habitat is extremely low, due to the fact that plants

175

growing in this location must be resistant to salt spray,

almost constant wind, full light intensity, high evaporation,

and relatively high temperatures (Johnson, et al., 1971).

The wildlife community which inhabits the beach is set to

a biological clock which is regulated by the tides. At low

tide, the beach (foreshore) is exposed and its inhabitants are

p-reyed upon by predators from the land, while at high tide

different predators attack from the sea (Johnson, et al., 1971).

Among the inhabitants of the foreshore area are such burrowing

forms as the ghost shrimp (Callianassa sp.), mole crabs (Lepidopa

sp.), and razor clams (Tagelus @R.), (Johnson, et al., 1971)

as well as various echinoderms such as sand dollars (Mellita sp.),

and brittle stars (Class Ophiruoides), (Frey and Howard, 1969).

Included in those species which prey on the foreshore during low

tide are birds such as plovers, sandpipers, scavengers such as

the fish crow and black vulture, and occasionally mammals such as

raccoons, oppossums, and otters. As the tide rises again to cover

the foreshore, predators include striped killifish (Fundulus

majolis), lizard fish (Syftodu foeteus) (Pearse, et al., 1942),

common tern (Stern lirunde), and the black skimmer (Rhynlops

nigra) (Johnson, et al., 1971) are found.

The upper beach and dunes serve as valuable nesting sites

for such bird species as the royal tern (Thadassues maximus),

American oyster-catcher (Haematopus pattiatus), and Wilson's

plover (Charadrius wilsonia), as well as such other animals as

the loggerhead turtle (Caretta caretta), and the Eastern mole

(Scalopu aquaticus).

176

Most of the species of animals found in this habitat depend

upon dune and beach stability, especially during their nesting

season. This factor critically links the vegetation of the

habitat with the preservation of the integrity of the wildlife

community, because there is eVidence that even minor modifica-

tion in the plant community can turn stable beach and dune

habitat into a shapeless mass of shifting sands (Johnson, et a!.,

1971).

The Barr:'-er Islands

The major barrier islands along Georgia's coast provide a

suitable habitat for a multitude of wildlife species. One of

the principal reasons for the diversity of wildlife is the

diversity of the plant community, which is dominated by a

pine and live oak canopy. Whitetailed deer, wild turkeys,

raccoons, feral hogs, snakes such as the diamond back rattler

and the cottonmouth water moccasin, and a wide array of songbirds

are common on these islands. Species such as foxes, wolves,

bobcats, pumas, and bears were present in the past but have been

largely exterminated (Johnson, et al., 1971).

Rare or unique species which still inhabit the islands

include the loggerhead turtle (Caretta caretta), the Cumberland

Island pocket gopher (Geomys cumberlandius), the St. Simons

Island raccoon (Procyo lotor litoreas), the Anastasia cotton

mouse Qeromyscus gossypinus anastasae), and the Blackbeard

Island deer (Odocoileus virginianus nigribarbis). The isolation

177

of barrier islands separated from the mainland shore has created

the environments for the development of unique species.

Fresh and brackish water ponds and sloughs also are important

habitats for wildlife. They provide food, shelter and nursery

areas for various species, and are a major source of fresh water

for island animals and birds.

The problem of habitat loss is compounded on islands isolated

from the mainland since there may be very little space into which

animals can expand their range in order to adjust for any habitat

lost or destroyed. In case of considerable habitAt loss, it is

quite probable that the wildlife affected will over-use the remain-

ing habitat and, subsequently, be subjected to natural population

controls such as starvation and disease. These natural controls

are usually devastating to entire populations and the recovery

periods are long. There is a need for in depth study and detailed

planning for the stable existence of the coastal island wildlife

species. Failure to control habitat modifications associated with

certain types of development "may seriously reduce or eliminate

some populations before their taxonomic position, range, distribu-

tion, and ecology can be determined" (Johnson, et al., 1971).

The Marsh and Estuary

The intimate interaction between the coastal marsh and estuary

often causes them to be con.sidered as a single ecological unit

(Schelske and Odum, 1961; Johnson, et al., 1971). As a unit, this

habitat supports vast numbers of wildlife species as well as being

178

an extremely important f2unctional element of' the coastal

ecosystem. Much of -the primary food energy is produced in

the tidal marshes and exported -to estuarine and open ocean

waters by the pulse of* the tide and flushing action of fresh

water rivers. Many fish and wildlife. species are dependent

upon the marsh and estuary for support during some phas6 of

their life cycle.

The marsh and estuary habitat serves as the spawning

ground and nursery area for i-iiany species of fish which spend

most of their life in the open ocean. These areas also provide

a hiding place from predators, Living conditions here are

suitable for wading birds; they provide important winter

feeding grounds for many species of migrating waterfowl.

Several mammals and various birds of prey are also supported

by this habitat, but these ani.nials are usually more closely

associated with the ecotone oi, edge whicI, exists along the

dry land periphery of the marsh arid estuary.

Georgia's marsh-estuarysyst-em supports an abundant sport

and commercial fishery. fish and shellfish of commercial value

include shrimp, blue crabs, shad, oysters, and king whiting.

Many other species, including snappers, groupers, triggerfish,

shark, black sea bass, macRerel and barracuda are popular

sport fishing species in offshore waters.

Rivers and, Fresh-Water River SwamDs

Fresh water river, swaff.ps are very productive wildlife

habitats in coastal Georgia. Species such as deer, raccoon,

179

squirrels and many aquatic birds and fish, among others, depend

upon the river environment for life support. In addition, the

river swamp provides many functions which are essential for the

support of the fish. Young fish, tadpoles, insects and other

organisms utilize sloughs and ponds of the river swamp for

spawning. These protected areas also serve as protected

nurseries and hiding areas for young fish. In addition, organic

matter accumulates on the forest floor, is decomposed by bacteria

and fungi, and eventually is washed into the river channel during

periods of flooding. This decomposed matter (called detritus) is

the beginning of the food chain which supports many of the fish

and wildlife species of the river. Many of the functions of the

fresh water river swamp parallel the salt water marsh and estuarine

system, although the particular species are different.

Fresh water rivers in the coastal counties support an abundant

fishery. Fish species with importance to sport fishing include

catfish, sunfish, crappie, and large mouth bass. Several species

of salt-water fish, such as striped bass and shad, enter the river

channel to spawn in fresh water areas. These fish are termed

anadromous. In addition to the true anadromous fish, many

salt water species penetrate the river mouths to a greater or

lesser distance to feed (such as red drum, spot, mullet, southern

flounder, etc.). Hence the fresh water river system is intricately

connected with the salt water environments.

180

The Nature of Existing Information

This brief report has highlighted the importance of

coastal Georgia wildlife. T'lliere is a great deal of additional

information on specific wildlife species available through the

Department of Natural Resources and published research reports

which this report has not summarized. In addition, further

research is needed on wildlife species and wildlife habitats,

especially habitats located in dry, upland areas where

pressures for urbanization may occur. Future research needs

include delineation of habitats for endangered species, and

research related to the inter-relationships of habitats and

species with each other. Finally, the effects of man's

activities on important wildlife habitats should be assessed

and integrated into local and State planning program.s.

181

SELECTED BIBLIOGRAPHY

Frey, R.*W., and Howard, J. H., 1968, A profile of biogenic
sedimentary structures in a Holo 'cene barrier island -
salt marsh complex, Georgia: Trans. Gulf Coast Assoc.
Geol. Soc., Vol. 19, p. 427-444.

Greaves, J., 1966, Some aspects of modern barrier beach develop-
ment; in Hoyt, J. H., Henry, V. J., Jr., and.Howard, J.D.,
(eds.), Pleistocene and Holocene Sediments, Sapelo Island,
Georgia and vicinity, 1953: Geol. Soc. Amer. Southeast.
Sect,., Guidebook for Field Trip No4 1, p. 40-63.

Henry, V. J., Jr., and Hoyt, J. H., 1968, Quaternary paralic and
shelf sediments of Georgia: Southeastern Geol., Vol. 9,
no. 4, p. 195-214.

Johnson, A. Sydney, Hillestad, Hilburn 0., Fanning, Sheryl A.,
and Shanholtzer, G. Frederick, 1971, An ecological survey
of the coastal region of Georgia: U.S. Department of the
Interior, National Park Service, 387 p.

Odum, Eugene P., 1971, Fundamentals of ecology: Philadelphia,
W. B. Saunders Co., 574 p.

Pearse, A. S., Humm, H. J., and Wharton, G. W., 1942, Ecology
of sand beaches at Beaufort, N.C., Ecol. Monogr., Vol. 12,
no. 2, p. 136-190.

Ryther, J. H., and Dunstan, W. M., 1971, Nitrogen, phosphorus
and eutrophication in the coastal marine environment:
Science, Vol. 171, p. 1008-1013.

Schelske, Claire L., and Odum, E. P., 1961, Mechanisms maintaining
high productivity in Georgia estuarines: Proc. Ann. Sessions
Gulf and Caribbean Fisheries Inst., Vol. 14, p. 75-80.

Smith, Robert Leo, 1974, Ecology and field biology, 2nd ed.: New
York, Harper and Row Publishers, Inc., 850 p.

Wharton, Charles H., 1974, What good is a salamander?: An address
to the 1974 Conference on Endangered Species of Georgia,
unpublished.

182

CHAPTER 7

Coastal Georgia%
Cultural Resources

Catherine M. Howett
Resource ?lanning Section
Office of Planning and Research
Department of Natural Resources

Coastal Zone Management Act

The Coastal Zone Management Act of 1972 recognizes that

"important ecological, cultural, historic, and aesthetic values

in the coastal zone which are essential to the well-being of all

citizens are being irretrievably damaged or lost. In response

to Congressional concern over these losses the Act requires

that the states include "an inventory and designation of areas

of particular concern in their management programs." (PL 92-583,

sections 301 and 30S). The effect of this legislation has

been to demand that culturally significant sites be properly

included in any consideration of the environmental resources

of the coastal lands. A Special Task rorce Committee at the

University of Georgia, in their analysis of the critical

needs of the coastal zone in this State, classified "major

183

historic and archaeological sites of natural significance or

of special value to the history and culture of Georgia" in their

first category of resources. This includes the sand dunes

of the barrier islands and endangered species of flora

and fauna, which are vital to the integrity of the coastal area

and possess a high to very high degree of sensitivity to cer-

tain kinds of human use or development. Apart from their

intrinsic value, it is the non-renewable nature of cultural

resources which makes their conservation so urgent: once de-

which the make available to us, a knowledge which must be

seen as part of our common inheritance and a public trust.

An Area of History

few places anywhere in America can boast a concentration of

historically significant places going back to man's earliest

presence equivalent to coastal Georgia's. Becaus parts of

the coast have been spared intensive industialization and

urbanization in this century, sites survive that might other-

wise have been lost. Nevertheless, many historical and archae-

ological sites have been permanently destroyed.

The first people following the river courses across the

slope of georgia to the sea ten thousand years ago settled

where the land ends, in a place of teeming life and primal

beauty. Since then, civilizations have layered up like the

silt of the river delta and have shifted and changed form like

the sand bars and the dunes. The Creek Indians, encountered

184

by the Spaniards, did not know what people had built the ancient

burial mounds; in our own time, scholars have debated whether

certain tabby ruins were mission buildings or the remains of

sugar mills on nineteenth cen---ury plantations.

History is so dense on the coast that it is difficult at

times to separate the strands. The peninsula called Severi-Mlle-

Band, on the Ogeechee River in Bryan County, seemed to Governor

John Reynolds in 1755 the only suitable location for a capltal

to replace Savannah, with which he was dissatisfied. "H-ardwicke

has a charming situatic.-ii, the winding of the river mak-ijig it a

peninsula and the only fit place for a capitol." He could not

have know that the Lamar Indian civili3ation had occupied the

site from appr-oX4mate"y 4.000 B.C. to 1500 A.D. Nor could be
L

have foreseen that i.n FebruarV of 1863, the C.S.S. "Nash%1411e",
L

refitted with heavy guns and renamed "Rattlesnake", would run

aground in Seven 11jile Reach while attempting to run the Union

blockade and be destroyed by the armored monitor, "Montauk".

Such a place typifies, in its layers of history, the entire

coastal region.

There are ironies as well as mysteries in these coinci-

dences of place. Governor Reynolds' appraisal of Savannah is

a case in point, in that Hardwick, even after repeated. attempts

at settlement, became one of Georgia's "dead" towns,, while

Savannah became the mecca for urban designers in our own time

who marvel at Oglethorpe's 1733 plan for the city. Or _onS4 der

bow the freedmen and runaways, who burned and sacked the lovely

town of Darien in 1863, fulfilled the prophecy of those stout

Highland founders of the town who had protested, twenty years

before, when the province of Georgia had petitioned for the

admission of slavery. "Introduce slaves", they wrote in a

counter-petition, "and we cannot but believe they will one day

return to be a scourge and a curse upon our children and.our

children's children". Fitting, too, that Jekyll Island, which

served in the seventeenth century as a supply station for

pirates and buccaneers, should become at the end of the nine-

teenth century the resort of the Morgans, Astors,-Goulds, and

Rockefellers who built sumptuous enclaves there.

"The Debatable Land"

Perhaps the most telling irony, though, is that over and

over again in its history the coast of Georgia has been a

"debatable land," even into our own day. The number of fort

sites on the historic maps is a good indication of the frequent

earnestness of the debate. The term "debatable land" was

actually the description used in an agreement between England

and Spain concerning the contested region below the Altamaha,

but it sums up well the whole long history of the struggle to

possess the varied riches of island and coastal lowland. The

Spanish conquistadors sought literal riches, wresting territory

from the Indians and enslaving them even while their missionaries

sought, without much success, to win their souls for the white

manis God. As early as the middle of the sixteenth century,

more than two hundred years before Oglethorpe's arrival, Spain

186

was forced to vigorously press its claim against that of the

French, on whose behalf Jean Ribaut had explored the coast,

presuming to name the St. Marys River the Seine, and the

Altamaha the Loire. Part of England's intention in chartering

the colony of Georgia was to provide a defense against the

Spanish in Florida, and major fortifications were established

at Savannah, Sunbury, Darien, St. Simons, St. Marys, and

Cumberland Island. OglethorpE! had achieved good relations with,

the Indians, who aided him against the Spanish, but there i@

ample evidence that the Indians eventually malized that they

were being driven out of their lands. The half-Indian Mary

Musgrove, Oglethorpe's interpreter, who had begun by convincing

the Yamacraw chief Tomochichi that he should allow the settle-

ment of Savannah, sixteen years later led an insurrection

demanding from the English thE! return of all the land that had

previously belonged to the CrE!eks.

When the Treaty of Paris (1763) ended Spain's presence in

Florida, a new argument overpossession of the coastal lands

came from the neighboring colony of South Carolina, whose

original charter included all the land to the St. Marys River.

That claim proved too difficu---t to make good, however, and in

just a few years the Revolution created a new set of friends

and enemies on the same ground. The French, whose privateers

had plundered the coastal towns in earlier days, sent a large

fleet from the West Indies to aid the colonies, and French

troops participated in the se--'ge of Savannah. The issue of

187

independence from England had produced divisions in Georgia

more bitter than those in other colonies. Many Loyalists fled

to Florida, organized a company of Rangers, and made that bor-

der once again the scene of sporadic guerilla fighting.

The ye ars after the war have been described as peaceful,

and certainly those were prosperous times in coastal Georgia.

The early agricultural adventures in silk manufacture, wine-

making, and the growing of exotic crops--citrus, olives, dates,

etc.--had long since given way to extensive cultivation of rice

and indigo, while lumbering, cattle-raising, and naval stores
L

had become important industries. It is interesting to recall,

however, -that the original impetus for the introduction of

slavery into Georgia had been 'the example of South Carolina's

success in growing rice-on large plantations, an enterprise

that slavery made feasible. So it is fair to say that behind

the affluence and genuine grace of the society that emerged

in the first half of the nineteenth century, another "debate"

went on, a moral one, whose issue would again mean war. Fannie

Kemble, the English actress who married Pierce Butler and came

-to his ancestral home on Georgia's coast only to discover that

she could not tolerate the life that slavery made possible

there, expressed the dilemma in her famous Journal: "...Wit-h

shame and earief of heart i say it, by their unpaid 'Labor I

ive--their nakedness clothes jrie, and their heavy toil mair.-

tains me in luxurious idieness." Journal of a Residence on a

Georgian 11--lantation was no-t published until 10363, and. so stirred

188

sentiment in England against the South that there was no l.on'ger

a possibility of English support for the Southern cause. If

Mrs. Stowe's book, in Lincoln's words, "began the great war",

Fannie Kemble's may have been responsible for determining its

course.

The plantations were burned, the countryside ravaged, the

economy destroyed in the war, and the period of Reconstruction

left bitternesses that one hundred years would not erase.

Sherman created a short-lived black separatist empire on St.

Catherines and Sapelo Islands, and Tunis Campbell, its governor,

later took over the ruined town of Darien with an army of

freedmen. Yankee carpetbaggers bought land on speculation,

and the ancient struggle for C-Dntrol on the coast went on

during the long years of recovery. These were the years in

which the possibilities of the coast as a vacation-resort area

became apparent, and at the end of the century many of the old

plantations were being purchased and restored as country estates

by millionaire businessmen.

That empire, too, has passed, but the nature of the coastal

region as a "debatable land" continues into our own time. Long-

time residents and those lately come seeking a livelihood or a

second home; investors and developers, ranging from those who

use the place-and-family names associated with a plantation

site for a subdivision, to the new conquistadors drawing up

plans for whole towns; conservationists and university resear-

chers seeking to protect the irreplaceable and complex ecology

189

of the coastal environment; federal and State agencies looking

for guidelines for producing growth with the ieast attendant

loss of quality--all of these forces figure in the new struggle.

What is most to be hoped for Georgia's coast is that the new

order which is bound to emerge from all of this will not be one

cut off from the colorful and meaningful past, without deep

roots in the communities that have already flourished there.

The history of the coastal region of Georgia is absolutely

dist-Lnctive, and unique solutions will have to be found for

preserving that inheritance.

Conservation of Historic and Archaeological Sites

The physical vestiges of that past are as vulnerable as

they are vital to our understanding of it. The archaeological

site, for example, exists as a hidden repository of evidence,

of knowledge essential to -the piecing together of man's history

and pre-history, giving the problem of its conservation a

special character, different from that of an historically

significant building. Archaeological sites can be excavated

and their store of data retrieved and recorded, so that the

land on which they are found may in most cases later serve

other functions. But until that investigation is accromplished

by competent authorities, a legacy that belongs to every citizen

of Georgia is threatened by premature disturbance of the earth

where archaeological sites exist.

At the federal leve-1, a of legislation E!-.XiSt-S to

protect archaeological and M.st-oric siteo. Th@@ Antirjuity Act

19o

of 1906 and the Historic Sites Act of 1935 extended assistance

and protection to properties of national significance through

the National Park Service of the Department of the Interio-r,

an authority broadened by the pivotal National Historic Preser-

vation Act of 196 6 to include properties of state, regional,

and local significance as well. This Act established the

National Register of Historic. Places, a "protective inventory"

of districts, sites, building7s, stractures and objects signifL-@

cant in American history, archi.tecture, archaeology a.,'Id culture.

The criteria for evaluation for a potential nomination to the

workmanship, feeling, and as;_@;ociation, and the following four

characteristics:

(1) Association with events that have Riade a signific+ant

contribution to the broad patterns of our history; or

(2) Association with t'-ie lives of persons significant

in our past; or

(3) Embodying the distinctIve characteristics of a type,

period, or method of constru2tion, or that represent the work

of a master, or that possess high artistic values, or that

represent a significant and distinguishable entity whose

components may lack individual distinction; or

(4) That have yielded, or may be likely to yield, infor-

mation important in prehistory or history.

The procedure for nomination to the Register requires

that application be made on behalf.of a property by a State

191

Liaison Officer appointed by the Governor to supervise the

-program within the State. In Georgia, the Historic Preserva-

tion Section of the Department of Natural Resources is the

agency responsible for surveys and nominations-

The National Historic Preservation Act also. provides a
program of matching federal funds, dispersed by a grant to the

state, to support the preservation work of public or-private

agencies and individuals. Perhaps most important for the cause

of conservation is the provision that no federally-financed

project may cause in any way the demolition or degradation-of

a National Register listing.

The Department ofTransportation Act of 1966 and the

National Environmental Policy Act of 1969 both acknowledge

that the preservation of historic and cultural resources is a

national.concern of high priority. They prohibit, except in

extreme circumstances, any actions on the part of a federal

ELgency that would impair protected sites, recognizing that

preservation is an environmental activity and not just the

concern of architects and historians. NEPA requires that

federal agencies prepare in advance a detailed description of

what adverse environmental consequences, if any, [email protected]

from a proposed project.

Executive Order 11593, "Protection and Enhancement of the

Cultural Environment", of May 1971, further assures that the

federal government will take the lead in "preserving, restoring,

and maintaining the historic and cultural environment of the

192

nation" by adequate care for the cultural resources under

federal ownership, nominating suitable sites, structures, and

objects to the National Register. The order also makes manda-

tory the institution by federal agencies of procedures which

would guarantee that their owr plans and programs contribute

to the "preservation and enhancement of non-federally owned

sites, structures, and objectE of historical significance."

Most recently, Public Law 93-291 (the Moss-Bennett Act

of 1974) provides that whenever a federally funded or licensed

activity threatens the loss of' significant data, an appropriate

historical or archaeological ELuthority may petition the Secretary

of the Interior to undertake Whatever surveys or reports are

needed to assure the recovery and protection of the data, or to

require that up to one percent of the project's funds be used

for that purpose. In January of 1975,the Housing and Community

Development Act of 1974 began providing block grants to

local governments through the Department of Housing and Urban

Development, allowing them to undertake historic preservation

projects as part of their urban renewal,programs.

Action at the State and Local Level

The importance of this legislat-ive support for the conser-

vation of cultural resources is that standards of concern are

established by which state, regional, and local agencies and
C,

interested groups may judge their own priorities; what the

federal government is saying, in effect, is that no action of

theirs shall do harm to any portion of our national heritage.

levi

To the extent that they can impose this judgment on non-federal

agencies or individuals, by withholding funding or licensing,

-they intend to do so. Developers who ignore these strictures

may find themselves subject to work stoppages, court injunctions,

and other time-consuming and costly delays. Potential as well

as actual historic or archaeological sites are protected, and

anyone considering alteration of such property should seek the

advice of the Historic Preservation Section of the Department

of Natural Resources in Atlanta before disturbing the property

in any way.

Georgia has willingly cooperated with the national effort

-to develop programs for the conservation of cultural resources.

-In 1972, Governor Jimmy Carter established the Georgia Heritage

Trust, whose task it is to discover, assess, acquire and protect

-those properties which ought to be enjoyed by all Georgians.

Under this program, Wormsloe and Hofwyl-Broadfield Plantations,

f
.or example, have been acquired for the enjoyment of all

Georgians.

The State effort has always depended for its effectiveness

on the valuable support and competency of local groups and

inoividuals interested in historic conservation. The newly-

revised edition of the State's Historic Preservation Handbook

-addresses itself to these groups and seeks to provide them with

-a working tool for "preservation, restoration, reconstruction,

-and rehabilitation" within their own communities. The emphasis

in the handbook is one with which coastal planners and citizens

need to be familiar:

In the 60's and 70's historic preservation has become
more concerned with ccmmmity planning and less with pure
history. No longer mainly saving a few super historical
sites,.historic preservation now concerns itself with all
manaade evidences of the past_*-individdally and collectively--
that by age or character contribute to the total environment.
Thus, an old building or group of buildings, orpub@ic square
that lends dignityand stability to a comminity, is given a
priority to be saved for its association with earlier genera-
tions and the foundations of the community. Preservation of
historic structures, objects, and sites is fundamentally tied...
with continued use and function-Whole districts become a
focus of attention as opposed to single structures. (Historic
Preservation Handbook, pg. 54.)

This concern with the larger environment should appeal

especially to those interested in the future of the coast,

because it suggeststhe possibility of new and more positive

approaches to the work of preServing the past, especially in

rural areas. An example of this new awareness of the cultural
significance of regions is furnished by the recent'purchase of

Drayton Hall, South Carolina, by the National Trust for Historic

Preservation and the Charleston Foundation. Drayton Hall is

in the Carolina low country twelve miles from Charleston, a

property of 625 acres of land and marsh on the Ashley River,

in a landscape punctuated by plantations, old rice fields, a

church and a fort--the analogy with parts of coastal Georgia

is quite clear. An article in the quarterly Historic Preserva-

tion describes what the expectations are for this area:

In the region survounding Drayton Hall are elements of
differemt activities from the area's history--from rice
growing to phosphate mining, from an old fort to an old church.
In addition to Drayton Hall there are two other major planta-
tions ... With coordinated planning by public and private
landowners along the Ashley, with adequate land protection,

195

easements and buffering on the other side of the river, with
carefully designed public park: land, the cultural, commercital
and social history of the Ashley River region can core alive
again not as a packaged restoration, but as a blending of
diverse elements into a dynamic historic and cultural landscape
region. At the same time, the river'would be environmentally
protected. (Ann Satterthwaite, "A New Meaning for Landscape",
Historic Preservation, July, 1973.)

Another ihter-esting precedent may be seen in the plans

for a unique historic trail system in western Montgomery County,

Maryland. Developed under grants from the National Endowment

for the Arts, the county planning board, and a private founda-

tion, the plan calls for a system of hiking, biking, canoeing',

and.horseback-rid--l.ng trails in a 100-square mile area, to be

integrated with natural sites and about 250 historic sites from

Indian times to the present. Historic themes, such as nineteenth-

century agriculture, railroading, and vernacular architecture

will be included. One trail, for example, will run from a sand-

stone quarry on the side of Sugarloaf Mountain following an old

railroad line to the Monocacy Aqueduct, built of stone from

tTie quarry. ("Hist-oric Trail System Planned in Maryland",

Preservation News, September, 1974, pg, 3.)

The more familiar notion of "shunpikes"--scenic roads

designed to attract travelers away from the interstates and

into the towns and countryside through which they are passing--

are going to work only if there is something really worth seeing

and experiencing; here again, isolated sites provide much less

incentive than an entire region that offers a unique and

pleasant landscape, rich in a history and culture that has

been made accessible to resident and visitor alike. No one

196

needs to argue the economic asset that tourism can provide for

a community, but the effort to attract tourists is often short-

sighted and opportunistic, When a community determines to

expend every effort to save itself from the universal sameness

that afflicts so many American towns and rural landscapes, when

it takes bold steps to see thELt part of what it has been in the

past shapes the look and feel of life there today, then other

Amer@cans will want a chance to come, and see, and learn, and

appreciate the unique achievement it represents.
But such towns and qountrysides do not just happen, and the

"bold steps" require the commitment of all those persons who

care about the future of the coast. The State of Georgia

and the federal government arE! clearly sympathetic to the need

for affirmative action to prevent continued loss of cultural

resources, but the initiative for determining what is needed

ought to come from the communities themselves. Existing State

and federal legislation needs the reinforcement of local

ordinances measured to the SPE!Cific needs of individual commun-

ities. Individuals, local government and community organiza-

tions must themselves contribute to on-going surveys of their

own resources that will continue to reveal possibilities for

the enhancement of their environment. Some kind of statement

of their philosophy and goals in the conservation of historic
and archaeological sites is needed, in order to determine what

legal controls will best effectuate the communityts intentions.

Officials and citizen groups must also keep themselves informed

197

about current thinking in preservation and planning studies,
such as the movement to encourage local governments to estabiish

a "revolving fund" for the temporary acquisition of threatened

sites or structures, or to grant reasonable tax exemptions to

those who undertake the restoration of buildings in whose wel-

fare the whole community has an interest. Legislation can also

make possible scenic and facade easements as devices for

preserving the character of a site without actual purchase.

The possibilities are endless for communities with a will to

see their vision become a reality.

Federal guidelines for the development of Coastal Zone

Management programs specifically state that "there is room to

exercise strengthened design and management imagination and

creativity under this program... While past research and planning

efforts have often been limited by existing law, policy, and

practices, the Act encourages creative approaches to action,

programs for orderly development, and preservation or restora-

tion of areas within the coastal zone for their conservation,

recreational, ecological, or esthetic values..." (Federal

which all those who love the coast, islanders and inlanders

alike, hope will be adequately met--and in time.

198

SELECTED BIBLIOGRAPHY

Capps, C. S., and Burney, E., 2.972, Colonial Georgia: Nashville,
Thomas Nelson Inc., 176 p.

Cate, M. D., and Wightman, O.S., 1970, Early days of coastal
Georgia: St. Simons Island, Fort Frederica Assoc., 235 p.
Coastal Area Planning and Development Commission,-1974,-CHIP
Report (description of hiEtoric sites-in coastal Georgia '
Brunswick, Georgia, Coastal Area Planning and Development
Commission,, pages unnumbered.

Francher' B., 1971, The lost 1E@gacy of Georgia's-golden isles:
Garden City, New York, Doubleday and Co., Inc., 216 p.

Historic Preservation Section, Georgia Department of Natural
Resources', 1974, Historic preservation handbook: Atlanta,
Georgia, Dept. of Natural Resources, 101 p.

Historic Savannah Foundation., Inc., n.d., Historic Savannah:
Savannah., Georgia, Historic Savannah Foundation, Inc., 247 p.

Savannah Writer's Project, 1947, Savannah river plantations:
Atlanta,.Georgia Historical Society, 473 p., reprinted in
1972 by the Reprint Co., 'Spartanburg, South Carolina.

Society for American Archaeology, n.d., Archaeology 4nd
archaeological resources - a guide for those planning to
use affect, or alter the land's surface: Washington,
D. C., Society of American Archaeology, 24 p.

Scruggs, C.P. ed., 1973, Georgia historical markers: Valdosta,
Georgia, Bay Tree Grove Publishers, 525 p.

Vanstory, B., 1970, Georgia's land of the golden isles: Athens,
Univ. of Georgia Press, 225 p.

199

CHAPTTR 8

Soils Information
for
Coastal Georgia

Ronald D. Lyberger
gesource' Planning Section
Office of Planning and Research
Department of gatural Resources

Soil Characteri3tics and Mapping

Soil is a natural resource and is one of the mos-F important

components of a natural resource inventory. Soil forms the upper

layer of the ground and results from the combined geologic,

hydrologic, biologic, and meteorologic processes. It is com-

posed of mineral matter, dead organic material, living organisms,

gases, water and dissolved substances which are the products of

climatic influences, geologic parent material, relief, vegeta-

tion, animal activity and time.

Much that is important to Taan takes place in the soil, and

.soil is, directly or indirectly., the foothold for much of the

life-supporting activities on earth. It and the associated

living organisms are the natura-_ medium for the growth of plants;

its properties and living organ--'-sms serve man by consuming

wastes and purifying water; its surface and mantle serve as a

foundation for buildings, roads, and most man-made structures.

Thus, the understanding of the dynamic, biophysical soil system

is of great assistance in determining the location of land uses

in order to sustain the uses with minimum deleterious effects.

Conversely, the ability of soils to sustain use is a function

of the type and amount of impact that natural processes and

mants activities have upon them.

The soils of the coastal region of Georgia have been or

are in the process of being mapped at two different levels of

detail; the general soil map and the detailed soil map. Through

the Resource Assessment Program of the Georgia Department of

Natural Resources, general soil maps (also called soil associa-

tion maps) prepared by 1--he Soil Conservation Service, U. S.

Department of Agriculture, are being made available at a scale

of 1" equals 1 mile (1:63,360)and 11' equals approximately 4

miles (1:250,000) for every county in the State. The nature

of the information is similar on both scales of maps.

A soil association is defined by the Soil Conservation

Service as:

a landscape that has distinctive proportional
pattern of soils. It normally consists of one or more
major soils and at least one minor soil, and it is named
for the major soils. The soils in one association may
occur in another, but in a different pattern. (Wilkes,
tt al.., 1974) -

2026

As a result of different uses, anticipated changing needs, and

t1le preparation of different count,,,, maps by different indivi-

duals, there are some discontinuities in data along county

boundaries. This is not a significant problem at this level

of generalization.

The more detailed soil surveyin which phases of soil

series form the mapping units,has not been completed for all

of the coastal region. Published reports have been completed

for Bryan and Chatham counties Milkes, et al., 1:974) and

McIntosh County (Byrd, et al.,19611), anithough the 1961 report

is not completely consistent with the 1974 report due to the

implementation of the Natlonal Cooperati\ie Survey, resulting

in certain changes in definition of scil serL-s and in procedure

during the period between thc. surveys. In addition, field

mapping has been completed for Glynn County, and -is in progress

for Camden and Tiberty Counties. SCS defines soil series as
.U %@

being made up of soils that have proftles (the sequence of

natural layers, or horizons, in a F@oil, extending from the

surface down into the parent material) almost alike. The.

soils in a series are then divided and mapped as phases on

the basis of differences in the surface texture, slope,

stoniness, or other characteristics since these affect the

use df the soils by man (Wilkes, et @,J_ , 197U). The

mapping is usually done at scales o[ 3:15,840 or 1-20,000.
The -two levels of mapping and description must be applied

in different ways in land use planning. The soil association

203

maps are useful for obtaining a general idea of the soils in

� region (a county, for example), comparing different parts of

� region, or locating large tracts that are suitable for a

certain kind of land use. They are not suitable for planning

the manageme.nt.of farms or -fields, or f.or selecting the exact

location of a road or building because of the variabt-lity in

characteristics of the soils-which may make up an association

(Wilkes, et al., 1974). For the latter purposes, the use of

the detailed soil surveys is necessary, since they can provide

reliable information for sites as small as three acres. Even

with the detailed surveys, further investigation in the form

of field work will be necessary for such things as checking

the specific site for a septic tank location or for completing

the final design and installation of engineering structures.

The major soils of the coastal region of Georgia (Bryan

and Chatham Counties being generally representative of the

region) are described by Wilkes, et al,, (1974) as chiefly having

- -a sandy surface layer over a loamy or sandy subsoil
or underlying layers.. These soils are mainly nearly
level or gently sloping and occur as broad, smooth
areas drained by wet depressions. They generally are
seasonally wet or almost always wet, except for the
better drained soils on the slight ridges and dune like
relief.

The factors that have led to the formation of this basic
pattern of soils are also described by Wilkeset al.,(1974),

and their material follows.

204

Parent Material

Parent material is the unconsolidated mass from which soil

forms. It largely determines the chemical and mineralogical

composition of a soil. The soils in Bryan and Chatham Counties

formed from transported materials.

The area shows evidence that the land was submerged by

the ocean in stages. This is especially true for those areas

less than 40 feet above sea level. The formation of barrier

islands, tidal marshes, and lagoons during each stage promoted

the sorting and mixing of the sediments. As the ocean retreated

to its present position, soil forming, processes developed the

soils as we know them today. Barrier islands of sand were

formed by tides and winds, and these islands were left as the

sea level dropped. The sandy Lakeland, Chipley, Osier, and

Kershaw soils developed in these sandy materials. Because of

their sandy origin, these soils have faintly developed horizons,

Lagoonal-tidal marsh sediments are characterized by mixed sand,

silt, and clay. Capers soils developed from clay in present

tidal marshes, and Pooler, Meggett, Ogeechee, and Cape Fear

soils developed from clayey deposits .In relics of lagoons and

tidal. marshes. Albany, Craven, Ellabelle, Pelham, Wahee, and

Olustee soils developed from mixed sand and clay sediments

that were affected by tidal streams and estuaries.

The older areas more than 40 feet above sea level have

been somewhat eroded, and the land features showing marine

205

influences are not so distinct as in the lower areas. The

soils at the higher elevation are similar in both chemical and

mineralogical composition to those of lower areas, and geologi-

cal erosion has exposed older deposits to the soil-forming

processes. Lucy and Dothan soils developed from older exposed

sediments.

The Angelina, Bibb, and Johnson soils formed in recent

alluvium that washed from the Coastal Plain and was deposited

by the larger streams. These materials are mixed sand and

clay and are within the stream flood plain.

A series of sand ridges are on the'northeast side of the

Ogeechee and . Canoochee Rivers and on the present barrier

islands. These ridges are quartz sand probably deposited by

wind. Kershaw soils formed in this sand.

Climate

Climate affects the formation of soils through its influ-

ence on the rate of weathering of rocks and on the decomposi-

tion of minerals and organic matter. It also affects biological

activity in the soils and the leaching and movement of weathered

materials through*the soils.

Bryan and Chatham Counties have a warm, moist climate.

The average annual temperature is about 660F. The temperature

averages about 510 in January and about 810 in July. The

average rainfall is between 45 and 50 inches. The warm, moist

climate promotes decomposition of organic matter almost the

year round, and only where the soils are waterlogged do

2r0M6

appreciable amounts of organic matter accumulate. The abundant

rainfall removes calcium, magnesium, and other basic elements

and replaces these cations with hydrogen. As a result, hydrogen
is the dominant cation and makes most of the soils highly acid

in reaction. Also, the movement of water through the soil

translocates other soluble material and colloidal matter into

the lower layers. The result is that the soils in Bryan and

Chatham Counties have chiefly a sandy surface layer over clay-

enriched layers. Exceptions are the Kershaw, Lakeland, and

Chipley soils, which formed in quartz sand.

Relief

Relief, or the differenCEZ in elevation, influences soil

formation through its effect on drainage, runoff, erosion, and

percolation of both we-iter an@. air through the soils.

Precipitation is not abscrbed by the soil where the rainfall

rate is faster than the infiltration rate or where the soil is

already saturated with free water. Low-lying areas stay wet for

extended periods. When a soil is wet, decomposition of plant

tissue is retarded. Consequently, more organic matter accumu-

lates in the surface layer of poorly drained and very poorly

drained soils than in better drained soils. Because relief is

low througnout most of the survey area, the soils in about 60
percent of the acreage are poorly drained or very poorly drained.

The greatest differences in relief in the survey area

occur in Bryan County west of the Ogeechee River and north of

the Canoochee River. Elevation increases from about 30 feet to

-2 M

about 80 feet above sea level within a mile. The gradient

is such that geological. eros-Lon has lowered the streams to
well below the general land surface. Most of the well-drained

soils occur in this part of the survev area.

in wet or Donded soils, movement of air is restricted and

the oxygen content is lower -than in well-arained soils. Oxygen

is removed from, some of the iron and aluminum compounds of -'Che

subsoil, causing gray mottles or dominant gray colors in -the

B horizon. This explains why the Pelham, Ellabelle, and othe'r

poorly drained and very poorly drained soils have dominant gray

colors just below -the surface layer, why the Ocilla and other

somewhat poorly drained soils have gray mottles in the upper

part of the B horizon, and why the Fuquay and other well-drained

soils have uniform, yellow to red colors free of gray mottles to

a. depth of at least 3 to it feet.

T--l -1. an
ts and Animals

Various. plants, aninials. and bacteria are active in the

soil-forming processes. The changes they bring about depend

mainly on the kinds of life processes peculiar to each. Plants

furnish most of -the organic matt-'er available to the soil.

Grass-type vegetation returns to the soil most of the plant

tissue produced ea.ch yea-e. Forest vegetation, however, returns

only part of the tissue in the form of Leaves, Organic matter

accumulates mainly in the surface Iayer.

In about 75 percent of the acueage of the survey area, the

soils formed under forest- vagetation, The organic mat--:7er

208

produced under forest vegetation is enough to give the

surface layer a dark color and an organic-matter content

of about 1 to 3 percent. It is not enough to add

appreciable amounts of organic matter to the surface

layer except where excess water slows decomposition. If

waterlogged the surface layer has higher organic-matter

content.and is darker and thicker than it is in drier

areas. The uprooting of trees by wind also affects the

formation of soils through the mixing of soil layers.

About 25 percent of the survey area has marsh or grass-

type vegetation, and the surface layer is higher in organic-

matter content than in forested areas. The surface layer of

some marsh soils contain as much as 15 percent organic matter.

Small animals, earthworms, insects, and micro-organisms

influence the formation of soils by mixing organic matter, into

the soil by helping to break down plant residue. Small animals

burrow into the soil and mix the layers. Earthworms and other

small invertebrates feed on the organic matter in the upper

few inches. They slowly but continually mix the soil material

and may alter it chemically. Bacteria, fungi, and other

micro-organisms hasten the decomposition of organic matter and

the weathering of minerals.

Time

The alteration of soil materials so that deep, distinct

layers develop in the soil requires time. The length of time

that geologic materials have remained in place is commonly

reflected in the distinctness and thickness of the horizons

209

in the soil profile.

Craven soils are formed in parent material that is less

than 35 feet above sea level and has distinct layers. Dothan

soils formed from geologically older parent material that is

more than about 70 feet above Sea level. They have had more

time to form and their clay-enriched layers are thicker than

those in the Craven soils. Also, Dothan soils have concentra-

tions of oxides in the form of nodules of ironstone and soft

linthite.

The sand soils that formed in homogeneous deposits of

quartz sand typically lack distinct genetic layers because

quartz sand resists alteration by the soil-forming processes.

210

SELECTED BIBLIOGRAPHY

Byrd, H. J., Aydelott, D. G., Bacon, D. D., and Stone, E. M.,
1959, Soil survey of McIntosh County, Georgia: Washington,
D. C., U.S. Department of Agriculture, Soil Conservation
Service, 62 p.

Wilkes, R. L., Johnson, J. H., Stoner, H. T., and Bacon, D. D.,
1974, Soil survey of Bryan and Chatham counties, Georgia:
Washington, D. C., U. S. Dept. of Agriculture, Soil
Conservation Service, 71 p.

CHAPTER 9

vegetation Information
for
Coastal Georgia

Ronald D. Lyberger
Resource Planning Section
Office of Planning and Research
Department of Natural Resources

The Importance and Use of Vegetation Information

Vegetation is the basic biotic component of an ecological

system. It is the immediate source of almost all of the

necessary minerals used by the animal components of an ecosys-

tem, it plays a fundamental role in the cycling of oxygen and

carbon through the processes of photosynthesis and respiration,

it functions as the energy-fixer for an ecosystem, and it acts

as a modifier of climate, pollution, and landscape form.

Much of the documented evidence concerning vegetation's

role in noise and air pollution abatement@ climatology, runoff

control, and landscape form is given in terms of vegetation

* General introductory material is taken from Chaney,
et al., 1974.

213

structure (the density and distribution of leaf structures

vertically, laterally, and horizontally) rather than species

present (floristics). Of course, the types of species present

determine the structure of the vegetation at any particular

point in time, but the structural changes that occur over time

can influence the floristics by various means and therefore

control, to a certain extent, the future structures.

For land use planning, consideration must be.gien to the

present structures, the longevity of those structures, the uses

being made of the structures, and the probable succeeding

structure. In addition, the effects of such events as fire,

cutting, cultivation, abandonment, and development on the

structure, and the probability of the spatial occurrence and

extent of the events must be considered. To make an analysis

of the extent to which such effects as soil erosion, runoff

and peak flow will increase as a result of various changes, the

vegetation structure must be described in a meaningful way.

Plant species generally do not occur singularly, but in

association with many other species of plants and animals. A

wide variety of factors interact to prduce patterns of

individuals and associations of species. These associations

are interacting organizations that utilize energy and raw

materials in such a way they form distinct living systems

(communities) with their own composition, structure, and

functional characteristics. As a result, vegetation is a

delicate integration of environmental condition and can, to

214

a certain extent, be used as an indicator of such conditions.

Species of plants are seldom restricted only to certain areas,

however. The occurrence of a single species is not usually

considered definitive proof of environmental conditions or

plant species relationships. The ratio of different species to

another often provides more useful clues. Billings (1965)

describes the advantages and disadvantages of using vegetation

as an indicator of environmental conditions (Table 9-1).

Classifying and mapping vegetation classes is not an easy

task. Each species has a range of tolerance for each of many

individual environmental factors, and its distribution

depends on its tolerance for and the distribution of those

environmental factors. Bozeman (1975) lists the principal

factors which affect the distribution of plant and animal

species (Table 94), The interaction of all these factors adds

up to a mosaic of different species of different ages occurring

in different places at different times.

Regardless of the system of mapping used, delineating the

vegetation boundaries is a prcblem, and the ultimate problem

lies in the nature of the vegetation. When plant communities

merge gradually, as they do in nature, the person preparing

maps is faced with the problem of establishing boundaries based

almost entirely on arbitrary decisions (Kuchler, 1973). The

basic principle of systems for synthesizing data from similar

stands is the repeated occurrence of groups of species or

structure. Often, characteristic or key species may be

215

Table 9-1

Vegetation As An Environmental Indicator

Disadvantages:

1) Because of the time necessary for growth, vegetation
usually lags somewhat behind the actual conditions that allow
it to be established. Trees, being slow growing, may indicate
conditions that occurred a long time ago; many trees can tell
us the date and extent of prehistoric forest fires. Thus, there
are also some advantages to this lag.

2) It is difficult to express the environmerital indica-
tions of vegetation in physical terms. Every vegetational
stand is a reflection of its past and present total environ-
ment, but it is difficult to transpose this information into
physical units that can be used quantitatively in equations.

Advantages:

1) Vegetation can indicate past environmental conditions
and events such as forest fires or past climatic cycles. No
physical instrument can do this.

2) Vegetation can tell us much about soil conditions:
salts, available nutrients, physical structure, capacity for
crop or timber yield. Once the original correlation is
established, the vegetation can be used as a soil,indicator
without digging a hole or taking soil samples.

3) Because of the difference in palatability of various
plant species to animals, vegetation is a very delicate indi-
cator of the kinds and numbers of animals present and the
grazing history of the land. Range ecologists can often tell
at a glance whether a given area is overgrazed or can profitably
carry more stock.

Source: Billings, W. D., 1965, Plants and the Ecosystem.

2160

Table 9-2
PrinciDal Factors Determining Plant - Animal Distribution

1. Climatic Factors (Primary Importance)
a) temperatures
mean annual, maximum and minimum
b) precipitation
distribution, amount, form
,c) atmospheric humidity
d) light
intensity, duration, quality
e) wind
f) potential evapotranspiration (an integrated expression)
g) water chemistry

2. Edaphic (Soil) Factors
a) available soil water
b) soil aeration, oxygen
c) soil temperature
d) quantity and nature of soil solutes
e) pH
f) soil texture

3. Biotic Factors
a) intra-and interspecific competition, food availability
b) grazing and predation pressures
c) parasitism (animal, fungal, bacterial, viral)
d) mutualistic relations-aips
e) man

4. Other Factors
a) fire, intensity and frequency
b) altitude and latitude
c) topographic effects o_-1L slope, exposure
d) pollution
pesticides
agrichemical run-off
industrial wastes
biologic - human waStes
animal wastes
e) geologic
biological history of organism
physical barriers to dispersal
geologic catastrophy and processes
f) chance distribution or dispersal

(Table continued on following page.)

Table 9-2

Principal Factors Determining Plant AnimalDistribution (Cont'd)

W Tolerance Range

ru
P4

Minimum Optimum Maximum

Temperature Gradient

Temperature response curve
for a typical animal, show-
ing maximum and minimum
temperature tolerance,
tolerance range, and optimum.
@Z @111

Source: John R. Bozeman, Department of Biology,
Georgia Southern College.
218

designated on the basis of their restriction to a particular

community. The problem again is that some areas are represen-

tative and some are not.

In addition to the problems mentioned, there lies a

larger argument which centers on the definition of vegetation

types and the definition and desired accuracy of the boundaries

considering variations in substratum (water, soil, rock) and

the amount of disturbance affecting the vegetation. Some

authors argue that plant species distributions shift along

environmental gradients, the resulting situation being not one

of clusters of similar species, but rather one of the species

of one area imperceptibly blending with those of contiguous

areas - a continuum of populations. Of late, Whittaker (1970),

a strong supporter of the continuum theory, has stated that

communities or associations are not mutually exclusive of

continuum, and that the exis-:ehce of both must be accepted.

Monk (1968) supports this view in his discussion of the

successional relationships of the vegetation of north-central

Florida, an area whose vegetation patterns are very similar to

those of mainland Georgia. Kuchler (1973) points out that it

is difficult to distinguish between transitions (ecotones)

between communities and the continuum. This is particularly

true in coastal Georgia where there are slight variations in

such factors as relief, slope, and water table level. Thus, the

boundaries between the community types are often broad transi-

tion zones (Bozeman, 1975; Monk, 1968). The problem then circles

219

back to the original consideration of boundaries.

Classifying vegetation means identifying "communities"

with natural or arbitrary boundaries (stands). No two stands

will be exactly alike, but various stands will resemble one

another more than other stands. Stands that resemble one

another more than other stands collectively make up a vegeta-

tional type.

Vegetation Information Available for Coastal Georgia

The vegetation of the coastal region of Georgia has been

classified and mapped as a scale of 11' = 1 mile as -a part of the

statewice Georgia Resource Assessment Program. The method by

which the categories were defined and mapped (largely based on

difference in physiographic location and physiognomic charac-

t-eristics observable on 1" = 1 mile aerial photo mosaics) means

that the mapping units are move appropriately designated as

vegetative cover types than as true community types. Monk (1968)

has defined community types for an area of north-central Florida

which are very similar to those found on the mainland of coastal

Georgia (Bozeman, 1975). The vegetation cover types are

generally analagous to the community types, but there are

differences due to the aggregation of elements of different

community types into a vegetation cover type because of (1) the

difficulty of distinguishing subtle difference in the mixture

of species between two closely related community types from the

111 = 1 mile aerial photo mosaics, and (2) the difficulty of

mapping at the 111 = 1 mile scale small areas of distinguishable

220

vegetation types.

In addition to the work done for the Georgia Resource

Assessment Program, there haVE! been several other descriptions

and mapping of selected areas of the coastal region. Johnson,

et al, (1971) provides a good overview of the natural history

and ecology of the marshes, islands, and estuarine waters.

They do not, however, discuss the mainland conditions. Detailed

vegetational analysis and mapping has been done for Cumberland

Island (Bozeman, 1975), St. Catherine's Island (McCormick,

Ashbaugh, 1972), and the marshes of McIntosh County (by DrI.

Robert Reimold and Richard Linthurst, Sapelo Island Marine

Institute, University of Georgia). These studies go well

beyond the level of detail of the mapping available for the

entire coastal region, and are more appropriate for site

specific, operational planning analyses. In that sense, these

latter studies are analogous -to the soil series and phase

mapping while the vegetation .-napping for the entire coast is

roughly comparable to the soil association mapping. Generally

speaking, stronger correlations exist between the vegetation

types identified in the individual detailed studies and the

soil series and phases than between the soil associations and

the vegetation types identified through the Georgia Resource

Assessment Program (Bozeman, 1975).

221

SELECTED BIBLIOGRAPHY

Billings, W. D., 1965, Plants and the ecosystem: Belmont, Calif.,
Wadsworth Pub. Co., 154 p.

Bozeman, John R., 1975 Unpublished, Georgia Southern College,
Statesboro, Georgia, personal comm.

Chaney, T., Golden, F., Maxwell, L., and Rogers, J.,-1974, A
natural resource inventory of thEl Stony Brook Watershed,
Mercer and Hunterdon counties, New Jersey: a study related
to regional and local land use planning: Unpub. Masters
Thesis, Dept. of Landscape Architecture and Regional Planning,
Univ. Penn. , Philadelphia, Pa. . 394 p.

Johnson, A. S., Hillestad, H. 0., Fanning, S. A., and Shanholtzer,
G. F., 1971, An ecological survey of the coastal region of
Georgia: U. S. Dept. of the Interior, National Park Serv-*L.ce,
387 p.

K-dchler, A. A.5 1973, Problems in classifying and mapping vegetation
for ecological regionalization: Ecology, Vol. 54, no. 3, p.
512-523.

McCormick, J. So*mes, H. A., and Ashbaugh, T. R., 1972, Vegetation
of St. Catherines Island, Ga.: NE!W York, Am. Museum of
Natural History,, 46 p.

Monk, D. C., 1968, Successional and environmental relationships
of the forest vegetation of north central Florida: American
Midland Naturalist, Vol. 79, no. 441, p. 457.

Whittaker, R. H.5 1970, Communities and ecosystems: London,
MacMillan and Co., 157 p.

222

CHAPTER 10

This chapter is excerpted fran An Ecological Survey
of the Coastal Region of_Georgia, A E222rt to the
National P@rk Service, by A.S. Johnson, H.Q. Hillestad,
S.A. Fanning, and G.F. Shanholtzer, August, 1971.
This material has been reproduced with the permission
of Dr. A.S. Johnson and the National Park Service.

THE MARSHES

A 4- to 6-mile band of marshland comprising about

393,000 acres (Spinner 1969) lies behind the barrier islands.

Nearly 286,000 acres of this is covered by a single species

of marsh grass, known as saltmarsh or smooth cordgrass.

(See Table 12 for scientific names of marsh plants not given

in the text.) The remaining 106,000 acres consists of

several other types of salt, brackish and freshwater marshes.

Formation and Sediment Characteristics

Tidal marshes are formed in conjunclE.:ion with barrier

island development. When sea levels rise, dune and beach

ridges become partially submerged. Water filling the trough

between these structures and the mainland or other barrier

islands is subject to rela--ively less energy perturbation

than open waters, and clay and silt sediments suspended in

the water are deposited, leaving a mud type substrate. In

time, salt tolerant marsh plants such as cordgrass stabilize

the area.

Deposi:@tion continually occurs on the tidal marsh, but

at a very slow rate. The added weight of the sediment

contributes to submergence and the accumulation of additional

sediments (Hoyt 1968d) As flood tides rise above creek

banks and inundate the marsh floor with a shallow layer of

223

water, the energy maintaining the sediments in a suspended
state is reduced, and the sediments drop out of suspension.

As the tides recede, some sediments are resuspended, but this
amount averages less than that. of flood tides. The receding

tide waters form an extensive drainage system of tidal creeks

and rivers.(Figure 26). Some tidal channels erode deeply

enough to expose Pleistocene sands and frequently penetrate

barrier island deposits (Hoyt et al. 1966).

Four sources contribute to the suspended material that

is deposited in the marsh: (1) continental shelf, (2)

mainland rilvers, (3) the marsh itself, and (4) organic

depositz. (Levy 1968). Continental rivers are the principal

source of this material which is distributed and sorted by

longshore currents, waves and tidal currents (Neiheisel and

Weaver 1967).

Superficial deposits are up to six feet deep. Cross-

bedding related to channeling is common (Henry and Hoyt 1968).

Total depths of recent marshes range from 30 to 50 feet (Hoyt

et al. 1964).

Grain size of sediments in the marsh range from clay to

fine sand. Large amounts of sand from reworked sandy

sediments are locally common. Teal and Kanwisher (1961) have

analyzed the salt marsh substratum for per cent sand, silt,

clay, organic matter,and roots. Their results show that

higher marsh sites have more sand and less organic matter

than lower marsh sites. When saturated on high tides, the

224

upper layers of marsh mud contain 50 to 70 per cent (wet

weight) water (ibid.) .

Two distinct layers of salt marsh sediments are

revealed in cross-section. The aerated and leached sediments

of the upper few centimeters are brown. The sediments below

are black and rich in reduced organic end products including

hydrogen, sulfide, methane, and ferrous compounds.

Although marsh soils are normally neutral or slightly

alkaline, some of them have the potential to become extremely

acid under certain conditions. When marsh soils containing

large amounts of organic matter are regularly flooded and

anaerobic conditions exist, the sulfates in sea water are

reduced and precipitated as sulfides. These conditions occur

most commonly at the mouths of larger rivers, in brackish

water marshes thickly vegetated with species such as big

cordgrass and reed cane. So long as .anaerobic conditions

prevail, soil pH remains high. But when the soils are

exposed to prolonged aeration (as in drained areas, dikes or

spoil areas), the sulfides are oxidized, and one of the

products is sulfuric acid. The soil becomes extremely acid

(pH may drop to as low as 2.0) and no plant growth can occur.

Such soils are then called "cat clays." The acidity is so

severe that it is not feasible to correct the condition by

liming and the area may remain barren for many years (Edelman

and Staveren 1958, Fleming and Alexander 1961).

225

Vegetation

The U. S. Fish and Wildlife Service has classified

the wetlands of the United States into 20 types (Shaw and

Fredine 1956). Six of these are coastal marshes occurring

in Georgia. 'These are characterized in Table,10. The

extent of these types of marsh on the Georgia coast is as

follows (Spinner 1969):

Types 12 and 13 31,700 acres

Types 15 and 16 650 acres

Type 17 74,850 acres

Type 18 285,650 acres

More specific marsh types may be recognized according

to plant associations. Many factors contribute to the

determination of plant composition of coastal marshes. These

include water levels and fluctuations, salinity, type of

substratum, acidity, available nutrients, and fire, among

others. Salinity and inundation are most important, and

gradients or zonations of vegetation related to these factors

are. commonly evident. Intolerance for salinity and
inundation prevent most species from occupying tidal salt

marshes (Table 11), and species diversity is greatest in

shallow. freshwater marshes. The harsh combination of

critical. limiting factors in the marsh produces conditions
allowing a few tolerant species such a competitive advantage
that they develop pure stands.. On-the Georgia coast, the

most extensive of these monospecifi.c marshes are smooth

226

TABLE 10. COASTAL WETLAND TYPES-OCCURRING ON THE GEORGIA COAST*

Type Water levels Characteristic species

12 Coastal shallow fresh 6 inches or less reedcane, big cordgrass, cat-tail,
marshes arrowhead, smartweed
13 Coastal deep fresh 6 inches to 3 feet cat-tail, wild rice. pickerp1wPed,
marshes giant cutgrass, pondweeds
15 Coastal salt flats Always wet, but glasswort, saltgrass
rarely inundated
.16 Coastal salt meadow Always wet, but saltmeadow cordgrass, saltgrass
rarely inundated

17 Irregular flooded Flooded irregularly needlerush
salt marsh

18 Regularly flooded 6 inches or more at smooth cordgrass
high tide

*From Shaw and Fredine 1956.

TABLE 11. RELATIVE SALT TOLERANCE OF SOME PLANTS
IMPORTANT IN THE COASTAL MARSHES OF GEORGIA*

Species Per cent salt

sawgrass 0.00-0.20

cat-tail 0.00-1.68

giant cutgrass 0.00-0.89

reedcane 0.00-2.04

southern bulrush 0.00-1.13

Olney's three-square bulrush 0.55-1.68

salt marsh bulrush 0.64-3.91

needlerush 0.12-4.43

big cordgrads 0.55-2.04

salt meadow cordgrass 0.12-3.91

smooth cordgrass 0.55-4.97

saltgrass 0.45-4.97

*Data from Penfound and Hathaway 1938.

228

cordgrass, needlerush and giant cutgrass.

Freshwater and brackish marshes

Freshwater marshes occur primarily near the mouths of

largermainland streams and are most extensive at the mouth

of the Altamaha River. They may extend for some distance up

the rivers before being replaced by cypress-gum or hardwood

swamps. Much of the area now covered by freshwater marsh was

cypress swamp before it was cleared and diked for rice

culture. Shallow freshwater marshes contain a variety of

species including cat-tails, several bulrushes, smartweeds,
aneilema, arrowhead, arrow arum, and others. The deeper

freshwater marshes are more extensive, occupying about 25,000

acres along the Georgia coast. in many arc-as this marsh type

is comprised almost exclusively of giant cutgrass. Stands of

sawgrass occur intermittently. Around the deeper margins of

the marsh, stands of cat-tail are common and wild rice occurs

in sporadic stands. In the deeper creeks and potholes,

submersed and floating-leaved plants are dominant.

As salinities increase to brackish conditions (about

0.5 to 2.0 per cent), giant cutgrass is replaced primarily

by big cordgrass and, to a lesser extent, salt marsh bulrush.

Salt marsh

Most indigenous plants cannot survive salinities

approaching sea strength;. they are replaced in the salt marsh

by a few species with high salinity tolerances. Included in

229

this group are smooth cordgrass, needle rush, saltgrass,

glasswort, salt meadow cordgrass, and sea oxeye (torrichia

frutescens)

salt marshes of the southeastern states have been

the subject of much study. Studies of plant associations in

the salt marshes of North Carolina have been reported by

Wells (1928), Reed (1947), Bourdeau and Adams (1956), and

Adams (1963)., Kurz and Wagner (1951) reported on salt marsh

vegetation.in Florida and at Charleston, South Carolina.

General treatments of salt marshes include those of Townsend

(1925), Ragotzkie et al. (1959), Chapman (1960), and Teal and

Teal (1969).

Of the local marsh plants only.smooth cordgrass is

adapted to both'the salinities and the tidal fluctuations of

the low tidal marsh. Teal and Teal (1969) describe the

adaptive mechanisms in smooth cordgrass that enable it to

exist in the marsh. Root membranes prevent the entry of much

salt into the plant, and the cells selectively absorb sodium

chloride to maintain osmotic-pressure and.prevent plasmolysis.

Special glands on the leaves-excrete excess salt.

Ducts in the.stems carry oxygen to the roots of the

plant,where it is used in the oxidation of iron sulfides to

soluble iron compounds that are used by the plant. The high

iron requirement of smooth cordgrass is one of the factors

that restrict it to the salt marsh (Adams 1963).

.Smooth cordgrass and most other salt.marsh plants

2 '%31

grow best in fresh water, at least under laboratory

conditions (Taylor 1939). But they do not commonly occur in

freshwater marshes, partly because they are unable to compete

with more vigorous.species. Their tolerance to salt stress

enables them to persist in the salt marsh free of competition.

Thus, zonation in the salt marsh is primarily related to

elevation as it determines frequency, depth and duration of

inundation, and soil salinity.

The zones of the salt marshes of the southeastern

United'States have been classified in various wayq (Wells

1928, Penfound 1952, Adanis 1963, Teal 1958, Stalter and

Batson 1969, and others). Following is a description of the

usual gradient in vegetation in Georgia salt marshes,

proceeding generally from the tidal creek landward (see

Figure 27). Unless otherwise indicated, Spartina used

hereafter refers to smooth cordgrass.

A portion of the creek banks exposed at every low tide

is devoid of vegetation. These banks are composed of sand,

mud or oyster shells. Slumping occurs- along some banks and

results in relatively large depo*its being exposed directly

to tidal currents. The upper slopes of the banks are

vegetated with smooth cordgrass. The cordgrass grows tallest

here (3 to 10 feet), and Teal (1958) designated this zone the

"tall Spartina edge marsh.." The cordgrass grows to about 3

feet on top of the levees. Teal (ibid.) called this zone the

"medium Spartina levee marsh."

O%PJ4
A&%j I

T
CB: SE MSLM SSLM SSHM I S-DM IJM LAND
IM I I I

CB-CIIEEK BANK;TSEM-TALL SPARTINA EDGE MARSH; MSLM-MEDIUM SPARTINA LEVEE MARSH;
SSLM - SHORT SPARTINA LOW MARSH; SSHM- SHORT SPARTINA HIGH MARSH; S-0m - SALICOItNIA-
IDI$TICHLIS; JM - JUNCUS MARSH.

Figure 27. Typical profile of a salt marsh showing the marsh
types d .escribed by Teal 1958. (Adapted and redrawn from Teal
1958.)
>P I

232

Behind the levees the marsh is thickly vegetated with

smooth cordgrass and is covered by every-tide for.several

hours each day. Sand content is 0 to 10 per cent (Teal 1958).

Teal (ibid.) called this area the "short S2artina low marsh."

Stalter and Batson (1969) designated this zone together with

the creek banks and levees as the "low low marsh."

With increasing elE!vation toward the edge of the

marsh, inundation is to a lesser depth and is for a shorter

period of time. Sand content is from 10 to 70 per cent

(Teal 1958), and salinity of the soil beneath the cordgrass

progressively increases (Penfound and Hathaway 1938, Bou@rdeau

and Adams 1956, and Stalter and Batson 1969). A dwarf form

of smooth cordgrass occurs in this zone that is probably a

genetic variant, environME!ntal conditions reinforcing the

differences between the two forms (Broughton and Webb 1963,

Stalter and Batson 1969). Teal (1958) termed this zone the

"short Spartina high marsh," and Stalter and Batson (1969)

called it the "high low marsh."

At elevations wherE! the marsh is flooded for only

about one hour each day, the dwarf Spartina gives way to

other species: notably glasswort, saltgrass, sea oxeye,and

sea lavender (Linomium carolinianum). Sard content is 85 to

95 per cent in this zone i:Teal 1958Y. This zone is called

the "Salicornia-Distichlis marsh" (Teal 1958) or the "low

high marsh" (Stalter and Batson 1969).

Sandy, unvegetated areas are locally common in the

higher portions of the marsh. These areas are commonly

called salt barrens or sa.'.t pans. Subject to infrequent

233

flooding and rapid evaporation, the barrens are too saline

to support vegetation. Glasswort occurs around the margins

and grades into saltgrass.

Salt meadow cordgrass (which, farther north on the

Atlantic coast, forms extensive meadows that are harvested

for hay, straw and upholstery stuffing) occurs on the

Georgia coast only at the rim of the marsh in a zone that

is flooded only a few times each week. Salinity decreases

abruptly in this zone (Bourdeau and Adams 1956). Salt

meadow cordgrass occurs only where relatively low salinities

prevail. Other plants that characterize this zone are high

tide bush (Iva frutescens), groundsel tree (Baccharis

halimifolia), and salt myrtle (Baccharis glomerulifolia).

Needlerus"k, irsh occurs at slightly higher elevations

that are rarely "Iooded,.especially where salinity is lower.

It occurs as a narrow zone around the salt marsh on the

islands, and forms extensive pure stands in many areas

adjacent to the mainland.

Marsh Fauna

Animals that complete their life cylces in the salt

marsh have morphological, physiological and behavioral

adaptations for coping with extremes of salinity, inundation

and exposure in the marsh, and the activity cycles of most

species are keyed to the tides.

Following is a discussion of some of the animal forms

occurring in the salt marsh: their distribution, abundance

234

and ecological -relationships. This information was obtained

from published material and from field observations by the

authors. The discussion is extended to include rails and

waterfowl in the freshwater marshes; otherwise, it is

restricted to animals of the salt marsh.

Vertebrates

Mammals.--The harshness of the salt marsh restricts

the numbers of resident mammals to a few species. Raccoons

are one of the most abundant mammals. Marsh rabbits are

common along the edges of the marsh'adjacent to high ground.

mink are more common than otter, but both of these carnivores

are seen infrequently. The rice rat is common along the

levees of tidal creeks.

Mammals that have adapted to living or feeding in the

marsh are highly mobile. Raccoons feed in the marsh at low

tide and are inactive at high tide regardless of whether it

is night or day. They retreat to the higher ground on the

mainland or islands at high tide or construct a bed of

cordgrass above the high tide level. In freshwater marshes

nearby, their activity is mostly nocturnal (Ivey 1948).

Mink and otter are well adapted to feeding in the aquatic

environment of the marsh, but they often retire to higher

ground for nesting and denning purposes. Kale (1965) stated

that mink may spend much of their life in the marsh. He

observed that they constructed beds of dead cordgrass on the

235

high ground of the marshes or used hollow tree trunks washed

into the marsh. The rice rat is well adapted to spend a 24-

hour day in the salt marsh. The rat constructs its own nest

in the tall Spartina or occupies an abaridoned nest of the

long-billed marsh wren (Sharp 1967).

Food for marsh mammals is abundant but is of limited

diversity. Raccoons are known to feed heavily upon fiddler

and squareback crabs (Uca spp. and Sesarma spp.), two of the

most abundant animals in the marshes. They also prey on the

eggs of diamondback terrapins (Coker 1906), clapper rails

(Oney 1954), and marsh wrens (Kale-1965). They dre not

considered a limiting factor on wren populations (ibid.).

The food habits of marsh mink are not known for the coastal

region of Georgia. Teal and Teal (1969) state that clams and

crabs are the principal foods of marsh mink in autumn, and

Wilson (1954) reported that fish occurred in 61 per cent of

the digestive tracts of mink from marshes of northeastern

North Carolina. Oney (1954) listed the mink as a predator

on clapper rail eggs. Otters feed mostly on fish. Wilson

(ibid.) found fish in over 90 per cent of otter digestive

tracts and fecal samples from northeastern North Carolina.

The rice rat is preferentially carnivorous. Studies

on Sapelo.Island (Sharp 1962, 1967) reveal that during the

summer the rats feed primarily on fiddler and squareback

crabs and the larvae of the rice borer, with other insects

occurring as incidental food items. In the fall, crabs were

236

the major food items, but small amounts of seed and fibrous
portions of smooth cordgrass also were used. Kale '(1965)

attributed considerable egg loss and nestling mortality of

the long-billed marsh wren to predation by rice rats. Sharp

(1967), however, found no remains of wrens in 22 rats

examined, and he suggested that the wren isonly an

incidental food item during the summer.

Marsh rabbits are characteristic of high marsh and

normally do not.occur in tidal salt marsh (Tomkins 1955,

Teal 1962). Marsh rabbits are strictly herbivorous, but

their exact food habits are unknown.

Harvest of marsh furbearers such as raccoon, mink and

otter generally is low in the coastal area because of the

low market value of pelts, especially Zrom this area. There

are an-estimated 300 fur trappers (Spinner 1969). Raccoons

are taken for food by a small number of hunters; there is no
closed season. The only management for mink and otter is t@e

regulation of harvest by an established -trapping season..

Birds.--Kale (1965) stated that three species of birds

were intimately associated with the salt raarsh community in

coastal Georgia. These are the long-billed marsh wren, the

clapper rail or marsh hen and the seaside sparrow. Kale

(ibid.) studied the ecology and bioenergetics of the marsh

wren, and Oney (1954) studied the biology, distribution and
limiting factors of the clapper rail in Georgia. The

seaside sparrow has not been intensively studied in Georgia.

237

The following discussion of the long-billed marsh

wren is based primarily on Kale's-(1965) study in the

vicinity of Sapelo Island. During the breeding season, the

marsh wren establishes territories averaging 100 square

meters in the.tall Spartina edge marsh. Singing males

establish breeding territories, and nesting and brood

rearing takes place within the territory. The peak of the

breeding season is May to July. Predation is the primary

cause of mortality of eggs and young. Major predators are

rice rats, raccoons and mink. However, mortality factors

are minor limiting factors on marsh wren populations; Kale

concluded that the highly developed territorial and colonial

behavior of the marsh wren was the principal factor limiting

population size. 'A discussion of food habits and

bioenergetics of the wren is included in the section on

food webs and energy flow.

The clapper rail is a common game bird in coastal

salt marshes. Clapper rails begin ne sting in the medium

,Spartina marsh early in April. Oney (1954).found that some.

nests were inundated by as much as 19 inches of water during

high tides and hatched successfully. Teal and Teal (1969) also

reported that the eggs of the marsh hen can withstand tidal

nundation. The major nest predators probably are raccoons,

mink and crows. The major food is the sqilareback crab, which

occurs in the soft mud areas of the tidal streambanks. Other

foods include fiddler crabs and periwinkle snails (Lit-torina

'238

irrorata). During the winter months when the crabs become

inactive, clapper rails shift to other foods. Richard Heard

(personal communication) observed that rails.feed on snails

(Melampus sp.) during cold weather.

The clapper rail is hunted by a small number of

hunters (5000 in 1968--Sp-Lnner 1969) during the high tides

of September-November. Prior to 1948 the rail harvest

approached 86,000 birds (Oney 1954). However, the use of

outboard motors in rail hunting was prohibited by federal law

beginning in 1948 and rail hunting declined sharply. Oney

(1954) recommended that outboard motors be allowed in rail

hunting.

The king rail, a c.*.:.ose relative of the clapper rail,

occurs in the freshwater and brackish marshes. Meanley

(1969) reported that king rails nested in giant cutgrass and

softstem bulrush along tidal canals on the Savannah National

Wildlife Refuge. The fiddler crab (Uca minax) of the latter

habitat is a preferred food of the rail. King rails feed on

freshwater insects, fish, crustaceans, and amphibians that

are abundant in mats of al-ligator'-weed in the canals and

ditches (Meanley 1969).

The willet, although common on beaches, is more common

in the salt marsh. It feeds on fiddler and squareback crabs

and periwinkle snails in the shcort
low marsh

(Tomkins 1965b).

The seaside sparrow has not been studied in coastal

239

Cborgia. Kale (1965) observed that in his study a-rea the

seaside sparrow fed primarily on the ground. Howell (1932)

listed small crabs, pelecypods, gastropods, dragonflies,

grasshoppers, spiders, and beetles as foods.

Wading birds use the marsh as a feeding and nesting

area. Five species frequent the marsh in large numbers

throughout the year. Other species occur seasonally in the

marsh, especially during the summer. Several large rookeries

are located on some of the marsh islands. (Figure 34, Appendix
41)`.' @,at@rdtAdkd_

Great blue herons, little blue herons, common egrets,

snowy egrets, and Louisiana herons are common residents of

the salt marshes. During high tides,- they feed in shallowly

flooded marsh grass. Snowy and common egrets are most

frequently encountered in the marsh at low tide. Cattle

egrets have been observed feeding on fiddler crabs near tidal

creeks; they feed more commonly near ag@ricultural areas

inland.

During the summer of 1970, a large wading bird rookery

was discovered on a marsh island in the-Altamaha River

(Figure 34). This rookery contained, in addition to large
numbers of white ibis, 75 to 100 nesting pairs of glossy

ibis. Hebard (1950) reported glossy ibis nesting in Georgia,
but Burleigh (1958) did not acknowledge his record, and

Sciple (1963) considered it too "tenuous" to accept. The

observation of glossy ibi's nesting in Georgia Ln 1970 fills

240

the hiatus in the breeding distribution for this'species as

rioted by Teal (1959).

Georgia is within the At lantic Flyway of migratory

waterfowl, and the coastal region is on the southern portion

of the flyway. The major species of ducks occurring in this

flyway include mallard, black, pintail, gadwall, baldpate,

shoveler, green-winged teal, scaup, ring-necked, and

canvasback. All of these species occur in varying numbers

along the Georgia coast., The number of waterfowl wintering

on the Georgia coast has been affected by refuges farther

north where many waterfowl spend the winter instead of

migrating farther south to their natural wintering areas.

For example, very few Canada geese now winter on the Georgia

coast, and populations of wintering mallards are significantly

reduced by northern refuges.

Most waterfowl management on the Georgia coast is on

lands owned by state and federal wildlife agencies. Despite

the fact that several areas in private ownership offer

excellent opportunities for.attracting waterfowl, little

private management is practiced as compared with South

Carolina, for example. There are a few raar6h areas near the

Satilla River that are under the manageirient of private

hunting clubs, but the management programs of these clubs

are minimal.

Freshwater marshes have greater variety of aquatic

Plants (Table 12) and are'most heavily used by waterfowl.

241

TABLE 12. SOME NATURALLY-OCCURRING PLANTS
OF SIGNIFICANCE IN WATERFOWL MANAGEMENT

Growth
Species habit Habitat2
Generally desirable
Muskgrass Chara. spp. Sb Fr, B
Spikerushes Eleocharis spp. E Fr, B
Soft-stem bulrush Scirpus validus E Fr
American 3-square bulrush Scirpus americannus E Fr
Olney's 3-square bulrush Scirpus olneyi E Fr, B
Salt marsh bulrush Scirp us robustus E B
Southern bulrush Scirpus californicus E Fr
Dwarf spikerush Eleocharis parvula E B
Giant foxtail grass Setaria magna E Fr
Wild rice Zizania aquatica. E Fr
Wild millet Echinochloa aquatica E Fr
Red-root sedge Lachnanthes caroliniana E Fr
Pondweed Potamogeton spp. Sb, Fl Fr, B
Bushy-pondweed Najas spp. Sb, F1 Fr, B
Wild celery Vallisneria americana. Sb Fr, B
Widgeon-grass Ruppia maritima Sb Sa
Aneilema Aneilema keisak E Fr
Water-shield Brasenia schreberi Fl Fr
Banana water-lily Nymphaea mexicana. F1 Fr
Smartweed Polygonum spp. E Fr

Generally undesirable
Needlerush Juncus roemerianus E B, Sa
Sawgrass Cladium spp. E Fr, B
Giant cutgrass Zizaniopsis miliacea E Fr, B
Smooth cordgrass Spartina alternifora E B, Sa
Salt meadow cordgrass Spartina patens E Sa
Big cordgrass Spartina cynosuroides E B
Reedcane Phragmites communis E Fr
Saltgrass Distichilis spicata E B, Sa
Pickerelweed Pontederia cordata E Fr
Golden club Orontium aquaticum E Fr
Arrow arum Peltandra virginica E Fr
Glasswort Salicornia spp. E Sa.
Alligator-weed Alternanthera philoxeroides E Fr
Yellow cow-lily Nuphar luteum Fl Fr
White water-lily Nymphaea odorata F1 Fr
Lotus Nelumbo spp. Fl, E Fr
Fanwort Cabomba caroliniana Sb, Fl Fr
Cat-tail Typha spp. E Fr
Arrowhead Sagittaria latifolia. E Fr
Waterweed Elodea canadensis Sb Fr
Bladderwort Utricularia spp. Sb, Fl Fr
Parrot's-feather Myriophyllum spp. Sb Fr
Coontail Ceratophyllum spp. Sb Fr

1 Sb = submersed, E = emergent, Fl = floating leaved
2 Fr = freshwater, B = brackish, Sa = saline
242

Except on Blackbeard Island, most coastal waterfowl

management is in old rice field.impoundments and newly diked

marsh in brackish water areas. Water contol devices are

strategically placed in the dikes, and water levelsare

manipulated to favor plants used by waterfowl. These include

in brackish impoundments submersed plants such as widgeon-

grass, muskgrass, and pondweed,.and emergent plants such as

dwarf spikerush and salt marsh bulrush, and in freshwater

impoundments smartweeds, aneilema and panic grasses.

The salt marshes (not including potholes and tidal

streams) have limited appeal as feeding areas for most

species of waterfowl. Lynch (1968) stated that the "true

worth of the southern tidal marsh lies not so much in its

direct appeal to waterfowl, but rather in its subtle

contributions to waterfowl food chains of adjacent

environments." Foods available to waterfowl in salt marshes

are mainly animal forms. In tidal creeks and potholes

widgeon-grass, a submersed aquatic, is the most important

duck food. Most dabbling and diving ducks utilize this plant.

The black duck, the most common duck using the salt marsh,

feeds primarily on snails. Many'spec .ies of waterfowl use

.areas,within the salt marsh-as resting and loafing areas

(Teal and Teal 1969).

The open waters of the tidal creeks are especially

attractive to diving ducks and other birds preferring animal

foods. Pied-billed grebes, red-breasted and hooded

243

mergansers, and large numbers of scaup commonly feed in the

tidal creeks.

At low tide the exposed mud flats of the tidal creeks

and marshes are preferred feeding areas for many species of

shorebirds such as willets and greater yellowlegs.

Species and preferred habitats of birds occurring on
the coast of Georgia are tabulated in Appendix 3. AMCttJJA

Re2tiles.--The diamondback terrapin is the only

reptile inhabiting the salt marsh throughout the year; it is

very common there. Formerly the diamondback was a "gourmet's

delight" and commanded high prices in northern markets; about

1.900, marketable females commonly sold for 30 to 36 dollars

per dozen (Coker 1906). Only the females reach a marketable

size of about six inche@; males seldom exceed 4 1/2 inches in

length. Experimental rearing studies were conducted by state

ZLnd federal agencies (Coker 1906; Hildebrand 1929, 1932;

Barney 1922), and although artificial production was

successful, it did not prove to be commercially profitable.
p

Small numbers of terrapins are currently taken from Georgia

marshes for personal use, and A few turtles are still sold

commercially.

The terrapin feeds mainly on periwihkles in the short

!c;partina marsh during periods of higli tides. Martof (1963)

reported that the peak in egg-laying in the marshes near

.Sapelo Island occurred late in May and early in June.

Female terrapins dig nests andlay their eggs slightly above

244

the high tide line. Raccoons are their main predators.

Alligators sometimes are observed in the tidal creeks

and sounds when they move to and from freshwater and

brackish marshes. A few alligators feed in the salt marsh.

Invertebrates

Approximately fifty species of insects occur in the

salt marshes (Teal and Teal 1969). Some of these complete

their life cycle in the marsh, others only breed or spend a

portion of their life cycle there. The salt marsh grasshopper

(Orchelin.um fidieinium) is restricted to the salt marsh and

is one of the few marsh insects that have been studied

intensively. Smalley (1960) found this species to be the

primary grazer of smooth cordgrass in Georgia. It is more

fully discussed in the section on food webs and energy flow.

The plant hopper, Prokelisia marginata, very common in the

marshes, sucks the juices oAf smooth cordgrass (Teal and Teal

1969).

An, ant, Crematogaster clara, feeds on the surface of

the cordgrass but lives within the stem of the plant. During

high tides, a specially adapted individual blocks the

entrance to the nest with its head and thus prevents the

colony from being flooded (Teal and Teal 1964).

Two species of salt marsh mosquitoes, occur on the

coast, Aedes taeniorhynchus and A. sollicitans. Aedes

taeniorhynchus. is the more common species, but A. sollicitans

is more aggressive in attacking humans (Bidlingmayer and

245

Schoof 1957). Both species breed above the intert'ida-1 zone

and lay their eggs in potholes and depressions that are

covered only by excessive amounts of rainfall or above-normal

high tides (King et al. 1960). Oviposition occurs on moist

soil or grassy areas within the zone (ibid.). Saltgrass is

a good indicator of these zones. However, it is not

essential to the breeding of either species as both commonly

breed in the cracks that occur in silt dredged from coastal

rivers (H. F. Schoof personal communication). The eggs can

withstand droughts of 4 to 6 months, and eggs may hatch

within hours following flooding. The detritus-feeding larvae

live in the tidal pools before transforming into adults.

The salt marsh mosquito is a vector of the dog

heartworm (Dirofilaria immitis). Although certain arboviruses

have been isolated from these mosquitoes, diseases of public

health significance, such as encephalitis, have not been

traced to A. taeniorhynchus -or A. sollicitans (H. F. Schoof

personal communication).

Three blood-sucking mid es, Culicoides furens, C.
.9

hollensis, and C. melleus, occur in the coastal area of

Georgia. These noxious insects breed in the marsh and are

verY-abundant during the summer.

Deer flies,(Chrysops spp.) are extremely common in the

coastal region. During the peak emergence in mid-May (Snoddy

1970), they are a severe annoyance to inhabitants of the area.
Breeding takes place in habitat similar to-the breeding sites

246

of salt marsh mosquitoes. However, the.larvae of deerflies

are semiaquatic; they are seldom found in areas which are

covered with tides.

Several species of crabs are common in the marsh.

The brown squareback crab (Sesarma cinereum) occurs on the

landward side of the marsh, and the purple squareback'crab

(S. reticulatum) and mud crab'(Eurytium limosum) occupy the

soft mud area on the levees of tidal creeks in the dense

cordgrass Oney 1954, Teal. 1958).

Teal (1958) studied the factors responsible for the

distribution of the three species of fiddler crabs in the

Georgia marsh. He determined that Uca pugnax and U. minax

select sites with a muddy substratum suitable for digging

burrows that do not collapse when flooded by tides. Uca

minax, the largest species, prefers marsh habitat in

brackish water and has the highest tolerance to fresh water.

Uca pugilator, commonly called the sand fiddler, selects

sandy marsh areas for its burrows. Teal noted that this

crab is exc luded from SOME! sandy marsh habitat by competi-

tion from the other two crabs. Uca pugilator plugs its

burrow before tidal inundation and, although the burrow is

in sandy marsh, it does not collapse because of air trapped

within the burrow (Teal and Teal 1969). All of the fiddlers

feed on organic detritus, and food is not a limiting factor

in their distribution (Teal 1958). All of the fiddler crabs

reach the adult stage In"one year.

247

Two species of sna.ils, the periwinkle and.Mela..-apus

1ineatus, are common in the salt marshes. The shell of the

r-eriwinkle is sealed by a horny, protective shield

loperculum) attached to the foot, an.adaptive protection

against dessication. Melampus is susceptible to dessication

because it has no operculum and therefore must remain near

damp sites. It moves up and down the coidgrass stalks with

the tides and feeds on detritus deposits on the plant.

Zxperiments with Melampus indicate that it has a biological

clock timed to tidal movements and begins to climb the

SpArtina stalks before the tidal water arrives (Teal and

Teal 1969).

Primary Production-

Primary productivity is the rate at which energy is

fixed or carbon is stored by the photosynthetic and,

chemosynthetic activities of producer (autotrophic) organisms.

The fixed.energy becomes available for consumption by consumer

(heterotrophic) organisms within the system. Therefore, any

analysis of total productivity is really an analysis of the

rate of plant growth (Schelske and Odum 1961).

Research at the University of Gebrgia's Marine

Institute reveals that the marsh-estuaries of Georgia are

highly productive ecosyst .ems. Schelske and Odum (1961) list

tiV4ty.
fiVe factors that are responsible for this high produc

These are (1) three types of primary production units,

SUppl4eS
(2) tidal ebb and flow, (3.) abundant of nutrientse

248

(4) rapid regeneration and conservation of nutrients, and

(5) year-round production with successive crops.

Primary production units are smooth cordgrass (Smalley

1959), benthic algae (Pomeroy 1959) and phytoplankton

(Ragotzkie 1959). Each producer unit occupies a different

"production niche." Spartina thrives in the intertidal zone

and produces two-thirds to three-fourths of the total

primary production. Net Spartina production is about 6580
kcal/m2/year (Teal 1962). Maximum production occurs during

the summer months. Mud algae contributes one-third to one-
fourth of the total primary produc@ivity (Schelske and Odum

1961). Pomeroy (1959) determined gross productivity to be
approximately 1800 kcal/m2/year and net production to be
1620 kcal/m2/ year. Thus the mud algae are the most efficient
producer systems in that only 180 kcal/m2/year is lost to

respiration. Production rates were approximately the same

throughout the year. During the summer, production was high

when marshes were flooded and light intensity was reduced.

However, in winter, when insolation was less, maximum

productivity occurred when the marsh was exposed. Phyto-

plankton production is greater than previously thought

(Schelske and Odum, 1961), but exact produdtion figures are

not-available. Schelske (1962) has determined that nutrients

are not a limiting factor on phytoplankton production.

However, high turbidity in estuarine waters limits light

penetration and'phytoplankton production below a depth of

249

about six feet. Phytoplankton production increases when the

marshis flooded because the surface area is four to five

times greater at high tide than at low.tide-(Ragotzkie and

Bryson 1955).

Tidal action is perhaps the most important factor

influencing primary production. -Twice-daily, tides.,,of

approximately.seven feet carry essential nutrients into the

marshes, export detritus and nutrients back into-e9tuaries,

and provide a large surface area for phytoplankton production.

Tidal flushing maintains a desirable vertical distribution of

nutrients and detritus.

Nutrients are abundant and probably are not a limiting

factor in estuarine production (Schelske and Odum 1961). The

nutrients of the fertile estuarine waters are contributed by

the marshes and not directly by inflowing rivers (Schelske

and Odum 1961, Thomas 1966).

A significant factor relating to primary production is

the rapid turnover of nutrients within the.system. Such is

the case in Georgia estuaries where nutrients are not "tied

upw but move rapidly through the system (Pomeroy 1960).

Fewer nutrients are needed for production if they are

continually available to organisms (Schelske and Odum 1961).

Nutrients are conser ved in the system by recycling;

they are repeatedly reused with little loss to the system.

The horse mussel, for example, is an important biological

agent in the recycling of phosphorus (Kiienzler 19611), an

250

essential element in estuarine production.

The three primary producers sustain production.on a

year-round basis (Schelske and Odum 196 1). Spaitina

produces two crops per year, mud algae produce at a fairly

constant rate, and phytoplankt6n contribute to produc tion

throughout the year (ibid.).

The combined effect of these factors produces one of

the most naturally fertile areas of the world. The net

production of the marshes and estuaries amounts to
approximately 2000 gm/m2/year or 10 t .ons (dry weight) per

acre of organic material (Odum 1961).

Energy Flow and Food-Webs

The most comprehensive studies-of energy flow in the

salt marsh have.been conducted at the University of Georgia's

Marine Institute. These studies have revealed that energy

stored by the primary producers follows two pathways through

the ecosystem (Figure 28): the grazer food chain and the
detritus food chain (Odum 19@1,-1963). The grazer food chain

has four primary consumers: -Orchelimum fidieinium (Smalley

1960), Prokelisia marginata, Trigonot ylus sp.,, and

Ischnodemus badius (Marples -1966). Smalley (1960) found

that during a period of about 100 days, salt marsh grass-

hoppers consumed approximately 2 per cent of the total

S2artina.crop. The utilization efficiency of salt marsh

grasshoppers (.57 per cent) was low because Spartina grows

throughout theyear at varying rates and because the
251

PRIMARY PRODUCERS

CORDGRASS
MUD ALGAE
PHYTOPLANKTON

2000gm/m2/yr

GRAZER DETRITUS
FOOD CHAINS FOOD CHAINS

SALT MARSH AQUATIC SYSTEMS

C R A B S
HERBIVOROUS INSECTS
S N A I L S

SPIDERS
PREDATORY INSECTS

CLAPPER RAIL
MARSH WREN
SEASIDE SPARROW DIAMONDBACK TERRAPIN
RICE RAT
RACCOON

Figure 28. Very generalized diagram of production and
utilization of organic matter in the salt marsh.
Approximately 5 per cent of the primary production is
utilized by the grazer food chain and 95 per cent by
the detritus food chain. Approximately 55 per cent
of the primary production is accounted for by the
salt marsh ecosystem, leaving 45 per cent available
for export into the aquatic system.
252

grasshopper has a short life span (4 months) and ingests
only leaves (Smalley 1960). Total'energy flow for the

grasshoppers and planthoppers is summarized in Table 13.

Odum (1961) reported that-only 5 per cent of the total

Spartina production is utilized by the herbivores Orchelimum

and Prokelisia; therefore, most of the.marsh production is

available to detritus-algae consumers..

The base of the detritus food chain is dead Spartina

which is attacked by microorganisms. Odum And de la Cruz

1967) stated that "organic detritus is the chief link

between primary and secondary productivity" (autotrophic

and heterotrophic levels). It has been suggested by several

workers that baqteria may be an important link in the food

chain, making some of the hard-to-digest materials available

as well as serving as food themselves. They 6olonize the

detritus particle and, upon ingestion, may be stripped off

and utilized as food (Burkholder and Bornside 1957; Teal

.1958, 1962; and Pomeroy et al. 1969). Burkholder and

Bornside (1957) estimated that the standing crop of bacteria
in the marsh is 107 bacteria per gm wet mud'.

Teal (1962) considered the important detritus-algae

feede'rs to be fiddler crabs, oligochaetes, periwinkle snails,

and nematodes among the deposit feeders, and Modiolus

demissus and Mamayunkia aestuarina, among the suspension

feeders. Marples (1966) reported that the periwinkle snail

and fiddler and squareback crabs were the most important

253

TABLE 13. SUIVARY OF ENERGY FLOW IN Tim SALT MAR-SIP

Gross Net
Organism production Respiration production

Producers

smooth cordgrass 34,580** 28,00.0 6,580
mud algae 1,800 180 1,620
phytoplankton - - no comparable data - - - -

.1I. Consumers

A. Primary
salt marsh grasshopper 29.4 18.6 10.8
plant hopper 275.0 205.0 70.-0
crab 206.0 171.0 35.0
annelid 35.0 26.0 9.0
neinatode 85.6 64.0 21.0
.mussel 56.0 39.0 17.0
snail 80.0 72.0 8.0

Total 766.4 595.6 170.8

B. Secondary
mud crab 27..2 21.9 5.3
clapper rail 1.7 1.6- 0.1
raccoon 1.7 1.6 0.1

'Total 30.6 25.1- 5.5

*Modified from Teal (1962).
.**Values in kcal/m2/yr.).

detritus feeders. Several investigators have determined

rates of energy flow for some of these forms. Teal (1962)

presents some of his own data and summarizes the data of

others relating to these detritus feeders.' This information

is summarized in Table 13.

Predaceous insects (secondary consumers) feed on the

herbivorous insects and in turn are fed upon by marsh wrens

and rice rats (tertiary consumers). The marsh wren was

shown by Kale (1965) to be also a secondary consumer on the

grazer food chain since it. also fed on herbivorous insects.

Predators of the detritus feeders include mud crabs, raccoonst

clapper rails (Teal 1962), and the diamondback terrapin.

Additional predators which have been observed to prey upon

fiddler crab* (detritus feeders) are.red drum, willet, white

ibis, herring gull, gull-billed tern, boat-tailed grackle,

whimbrel, snowy egret, cattle egret, and little blue heron.

Table 13 summarizes the energy flow data presented by Teal

(ibid.) for the mud crab, raccoon and clapper rail.

The utilization of organic matter.in the salt marsh

(Figure 28) accounts for approximately 55 per cent,of the

total primary productivity. Therefore, roughly 45 per cent

(4.5 tons per acre)of the production is-available for

utilization by and support of an abundance of estuarine

animals (Teal 1962), including numerous finfish and shrimp

which sustain an important industry.

In summary, 6.1 per cent of incident light energy is

255

utilized by the salt marsh in gross production and 1.4 per

2
cent of light energy becomes net -production (2000 gm'/m /yr) .
Fift-y-five per cent of the net production is consumed by the
marsh inhabitants and 45 per cent is available for. export

into the estuarine system (Odum. 1961, Teal 1962).

,(bibliography contained at the end of section on "Open Marine and Estuarine
Waters")

256

E R11
CHAPTE

This chapter is excerpted from An Ecological Survey
of the Coastal Region of Georgia, A Report to the
National Park Service, by A.S. Johnson, H.U. Hillestad,
S.A. FannEig-, 'and G.F. Shanholtzer, August, 1971.
This rnaterial has been reproduced with the permission
of Dr. A.S. Johnson and the National Park Service.

THE OPEN MARINE ANI ESTUARINE WATERS

The marshes, being protected by the barrier islands

from frontal assault by the ocean, interact with the ocean

indirectly, through systems of tidal streams and estuaries
,,, MoT-"dAAecL
(Figu're 26). Estuaries are semi-enclosed bodies of water

having free connections with the open sea and having sea

water measurably diluted with fresh water derived from'land

drainage (Pritchard 1967a). The estuaries of Georgia

connect with the sea through the sounds that separate the

barrier islands. These are north to south from.the Savannah

River Entrance to the St. Marys River Entrance: Wassaw

Sound, Ossabaw Sound, St. Catherines Sound, Sapelo Sound,

Doboy Sound, Altamaha Sound, St. Simons Sound, and St.

Andrews Sound. Salt water is diluted by fresh water from

the Savannah, Ogeechee, Altamaha, Satilla, and St. Marys

xivers. The coastal or inshore waters extend from the mouths

of the sounds and from the barrier beaches to a depth of about

60 feet. The offshore waters of the continental shelf lie

beyond.

The continental shelf along the'Georgia coast is 70

to 80 miles wide with a gentle slope of about two feet per

mile (Henry and Hoyt 1968). It is covered by sediments

deposited during low stands of the sea. The topography of

the continental shelf off the Georgia coast is shown in

257

Figure 29. The poorly defined valley in the shelf east of
Sapelo Island is thought to be a filled valley once occupied
by.-the Altamaha River (Pilkey and Giles 196.5). An abrupt

increase in slope of descent occurs at 50 to 80 meters

(ibid.). This break marks the edge of the continental shelf

and the beginning of the upper continental slope. Seaward-

of the continental shelf is the Blake Plateau, an

intermediate plateau between the continental shelf and the

ocean basin. The Blake Plateau averages 700 to 1000 meters

depth (Pilkey and Terlecky 1966).

The coastal (inshore) waters are somewhat diluted

with fresh water; they are turbid, and they are most

productive. Beyond the continental slope, ocean, waters are

clear and relatively unproductive. The waters of the

continental shelf are of intermediate fertility.

Physical Characteristics

P-Itterns of circulation

The waters of the Georgia coast are subject to man,,,r

interacting forces that produce complicated patterns of
,`rculation that to a lagge ex tent determine the distribution
O!sediments, nutrients, oxygen, temperature, salinity, food,
4.nd planktonic forms of larval and adult organisms.

Ocean currents are produced by wind, gravity and
."ferences in density of' water strata. Surface currents
cl',Mnsonly are caused by the stress that winds exert on the

258

...........

:*i::*,
..... ..... . . . . . . . .

.... ............
............. x..

.............
.X ............
..........
..............
...........

....... .....
.. ........
...... ....
. ..... ....
..........

......... .

............
....... .......

...........
..........
............... ........
................ ......

....... ....
............
.............
GEORGIA
SHELF
TOPOGRAPHY

SHELF CONTOUR INTS 5 METERS
SLOPE CONTOUR INT:30METERS

SCALE I N MILES

0 5 10 15 20 25

Figure 29. Bottom topography of the continental shelf off Georgia.
Contour interval changes at continental shelf. (Adapted and redrawn
from Pilkey and Giles 19065.)

water surface; tidal currents are caused by the interacting

forces of gravity of the, earth, the moon and the sun; and

density currents are related to differences in density that

result from variations in temperature and salinity within a

body of water.

The Gulf Stream, a northerly flowing current of warm,

saline water beyond the continental slope, is a density

current. It results from warm, tropical waters spreading

northward over the Tore dense polar waters which sink and

flow toward the equator. The currents are deflected from

direct poleward flow by wind friction, earth rotation and

land masses. Eddies form inshore from the Gulf Stream and

may-be responsible, in part, for the southward -,---ranspo--t of

sediment along the Georgia coast.

The movement of the waters inshore from the Gulf

Stream has not been studied systematically and must be

assumed from a limited number of observations. Bumpus and

Lauzier*(1965) summarized data from drift bottles on seasonal

direction of surface currents of the continental shelf from

Newfoundland to Florida. The data from Georgia, admittedly
inadequate, indicate currents flowing as follows: winter--

Southerly; spring--northerly; summer--southerly and
northerly; fall--southerly. Bellinger (1968) reports that
flow is southward during the summer, fall, and winter,

extending out 20-30 miles during the summer and about 45
miles during the other seasons. Rates of surface flow vary

260

densities of the water masses is less. As temperatures

begin to rise in the spring, inshore waters warm faster and

the temperature gradient gradually disappears, but the

salinity gradient is steeper than at any other time of the

year because of heavy freshwater discharge. The lessening

temperature gradient and steepening salinity gradient

coMpensate to produce water of similar densities inshore and

offshore. These shifts in densities probably result in slow,

seasonal water movements. They could be responsible for

setting up the inshore-offshore components mentioned by

Bellinger (1968).

Tidal currents are the horizontal movements of water

which, unlike the currents caused by wind and density

differences, are periodic. The tidal component is most

pronounced in narrows such as entrances to bays and

constricted parts of rivers. Tidal currents for the Georgia

estuaries were given by Haight (1938).

The Georgia coast is subject twice daily to tides

approximately the same height. The height of the tide

increases from about 5 1/2 feet at Nassau Sound, Florida, to

about 7 feet near Savannah. The tidal movement of saline

waters into the estuaries and the drainage of rivers into

them cause the complicated hydrologic patterns characteristic

of estuaries.

Pritchard (1967b) described four hypothetical

circulation patterns for estuariest two of which may be

261

applicable to Georgia estuaries. The moderately stratified

estuary is one in which tidal action serves as the dominant

force mixing fresh and salt waters. The Savannah River

exhibits this type of circulation. In an estuary with no

tide or friction, undiluted-sea water would extend upstream

.along the bottom to a point where the river surface was

.approximately at sea level-. The less dense fresh water

would flow seaward on top of the salt water. When there is

tidal action, as in the moderately stratified estuary,

turbulence carries fresh water downward and salt water

upward. The galt content of both layers increases toward

the sea, but at any given point the bottom layer is more

saline than the top. Vertically homogeneous estuaries occur

where tidal mixing is vigorous and freshwater input is low.

In this case vertical salinity stratification breaks down.

The circulation patterns and physical characteristi.cs

of only a few Georgia estuaries have been studied. The

Savannah River, a moderately stratified estuary, has been

studied by the U. S. Corps of Engineers. It has a drainage

area of approximately 9850 square miles and an average
discharg.e of 11,290 cfs (U. S. GC-1ological Survey 1960). it
is tidal for approximately 50 miles upstream. A physical

model of the river has been designed in order to study

shoaling (U. S. Army Corps of Engineers 1949). Figure 30

shows the tidal currents at ebb and flood tides as predicted

by the model.

262

t Yj
I IF,

\A,

t t W
A
IA

4
tz
t ttiolL
@/ 44
Aoljt, f fit

rigure 30. Direction of tidal curren-.s at ebb and flood tides in the Savannah area as
tt

predicted by a physical model (redrawn from U. S. Corps of Engineers 1949).

263

The Altamaha River has the greatest discharge along

the Georgia coast. It has a drainage area of approximately

13,600 square miles and an average discharge of 12,600 cfs

,[u. S. Geological Survey 1959). Several miles from the

ocean it divides into a number of distributaries (Darien,

1jutler, Champney, and South Altamaha) which empty into

i@ltamaha Sound and to a lesser extent into Doboy and St.

Simons sounds. The hydrography of this river has been

s;tudied to only a limited extent. Neiheisel (1965), in a

study of the causes of shoaling in Brunswick Harbor, presents

information on the mixing and flow of water in Brunswick

H:arbor as influenced by the Altamaha River. Discharge into

Brunswick Harbor, a well-mixed estuary, by the Turtle River

is negligible. However, during maximum peaks of discharge,

fresher water from the Altamaha enters the Harbor through

the Mackay and Frederica rivers. -The water discharged

through the Altamaha Sound into the ocean is moved along the

shore and enters Brunswick Harbor through the sound entrance.

Salinity measurements in the Mackay and Frederica rivers show

that they are partially mixedestuaries.with some density

stratification during a period of low discharge. During

higher discharge it is assumed that the interface would
Lecome sharper and move toward the harbor. Salinities were

approximately 5 parts per thousand in the Mackay River near
Altamaha Sound and approximately 20 parts per thousand near
St. Simons sound (Neiheisel 1965).

0 FkA
121.1

The hydrography of Doboy Sound, recently studied by
Levy (1969), is also affected by the Altamaha Rive@r. During

ebb tide fresh-water from the Altamaha flows seaward through

the Darien-Rockdedundy complex.into Doboy Sound through the

Black, South, and North rivers. During mid-ebb this water

flows out the mouth of Doboy Sound along the south shore

while water from the sounds leaves by the north shore.

Because of the limited fresh water flow, Doboy Sound is a

mixed estuary (at least during the summer months) with no

recognizable salt wedge and little vertical stratification.

A salt wedge is present -just seaward of the inlet, where

less saline, highly turbid waters of the longshore drift

overlie more saline oceanic waters. This moves shoreward on

flood tide.

Ragotzkie and Bryson (1955) studied the Duplin River,

a tidal river located near Sapelo Island and opening into

Doboy Sound. Having no significant fresh water source, it,

is an elongated tidal bay about 5.9 miles long with a tidal

exCursion, of about 3 miles. At mean low water the river

has a relatively small horizontal area; however, at 6 feet

above mean low water the water flows over the banks and onto

the salt marsh. The area, of marsh flooddd increases rapidly

as the level of water rises. From one-t-hird to two-thirds

Of the volume of water entering the Duplin River on a rising

tide leaves the river to.flood the marsh. The volume of

water involved is greatly increased with relatively small

265

C)uaternaky sediments consisting of coarse-grained particles

are less than 100 feet thick and are mostly of Pleistocene

origin (ibid.).

Carbonate contents of shelf sediments are discussed

by Gorsline (1963), Pilkey (1964) and Pilkey et al.(1969).

Carbonates average less than 25 per cent'over most of the

shelf and consist mostly of mollusks. Carbonate cQntent

increases seaward to about 50 per cent on the shelf edge and

nearly 100 per cent on the upper slope where forami nifera

are the major components (Pilkey 1964). This increase toward

the shelf edge probably results from the diminishing

contribution of terrigenous materials.

The presence of oolites off the Georgia coast is

indicative of pre-existing shorelineconditions and low

sedimentation rates, and the abrasive history of the

carbonate fraction indicates that former shorelines in this

area, like those of the present, were subject to relatively

low wave energies (Pilkey et al. 1969).

Phosphorite averages about 1.1 per cent of shelf

sediments (Henry and Hoyt 1968). Present day rivers

apparently lack phosphorite in their sediment loads, yet all

shelf samples and most estuarine sands contain these grains

in varying amounts (Pilkey and Terlecky 1966). Pevear and

Pilkey (1966) and Pilkey and Terlecky (1966) concluded that

much of the sands and nearshore fine sediments originate

from landward transport from outer portions of the shelf and

'266

increases in tidal height. The waterways are subject to

high turbulence as this large volume of water enters and

leaves. Mixing is rapid and no stratification long can be

maintained under these conditions.

Sediments

Coastal sediments have been the subject of

considerable study since 1960. Much of this work was done

by the University of Georgia Marine Institute. Papers

dealing with sediments of the continental shelf (shelf

sediments) and of the shallow waters near shore (paralic

sediments) are reviewed by Henry and Hoyt (1968).

Previous sections of this report have described origins,

composition, depositional patternsand migrations of sediments

of offshore bars, beaches, and dunes, and marshes. The

following summary is restricted to some ecologically

important aspects of shelf and inshore sediments not

previously discussed.

Nearshore, a narrow band of fine sands is considered

to be of Recent origin (Pilkey and Frankenberg 1964).

Minerals of mainland (terrigenous) origin (mainly quartz)

are the dominant constituents (Henry and Hoyt 1968).

A relatively sharp boundary between Pleistocene and

Recent sediments occurs quite consistently at about 6 fathoms,

general ly about 12 miles offshore Wilkey and Frankenberg

1964). Cenozoic deposits on the continental shelf range

from 2000 to 2500 feet deep (Henry and Hoyt 1968).

267

not from mainland rivers. Shelf phosphorite has evidently

been derived from either Pleistocene rivers or from ancient

phosphatic sediment outcrops on the shelf.

The heavy mineral fraction of shelf sediments averages

less than 0.5 per cent (Hen--y and Hoyt 1968). The heavy

mineral suite includes staurolite, kyanite, garnet, zircon,

epidote, pyroxenes, amphiboles, rutile, and tourmaline

(Pilkey 1963). Heavy mineral distributions are frequently

useful aids in the determination of sediment origins, but

heavy minerals in shelf sediments off the Georgia coast show

minimal variation because of their. common origin in Piedmont

rivers (Pilkey 1963).

Fauna of Estuaries and Inshore Waters

Vertebrates

Fishes.--The waters off the coast of Georgia*support

a variety of fishes related to the diversity of habitat.

Some estuarine species enter fresh water to spawn and a few

freshwater species enter the brackish estuaries. Some

species are restricted to the estuaries and inshore waters

.and some are restricted to the waters of the continental

shelf. But many species migrate between these habitats at

various stages in their life cycles, and the estuaries are

vitally important as nursery grounds and spawning grounds

for many commercially important species harvested-on the

continental shelf. Stroud (1971) listed the species that

-268

are dependent upon the.estuaries during some stage in their

lives and reported that they comprised 63 per cent of the

Atlantic catch. He calculatedthat, for the Atlantic coast

generally, each acre of estuarine habitat produces a yield

of 535 pounds on the continental shelf.

The continental shelf off Georgia genqrally is

composed of shifting sediments and does not provide good fish

habitat. However, a coral reef, or live bottom, recently,has
been discovered 16 miles due east of Cabretta Inlet o@ Sapelo

Island. Such reefs provide a stable surface for the

attachment of organisms important in the food chain.

Artificial reefs also are being established by the Georgia

Game and Fish Commission.

There has been relatively -little work,on the ecology

of fishes of the Atlantic coast of the southeastern United

States. Tagatz and Dudley (1961) studied the seasonality of

fishes in four coastal habitats near Beaufort, North Carolina,

and Tagatz (1968) and McLane (1955) surveyed the fishes of

the St. Johns River, Florida.

Some pertinent work has been.done off the Georgia

coast. Anderson (1968) surveyed.the fishes caught by shrimp

trawling from South Carolina to northeas@ern Florida from

1931 to 1935. Miller and Jorgenson (1969) studied the

seasonal abundance and lenq-th frequencies of fishes collected

in two habitats and presented a list of fishes collected at

a freshwater station in the Altamaha River. They made

269

thorough surveys by seining at a beach habitat on St. Simons
Island and two high marsh stations, one near Jekyli Island

and one near Meridian, Georgia. Dahlberg and Heard (1969)

su rveyed the common inshore elasmobranchs of the Georgia

coast. Dahlberg and Odum (1970) sampled fish populations -in

St. Catherines and Sapelo sounds by trawling at three-week

intervals for 13 months. Struhsaker (1969) presented a list

of fishes taken during five years of exploratory trawling on

the continental shelf off Georgia and other southeastern

states.

A list of fishes that may be encountered in Georgia's

coastal waters is included (Appendix 1).

Reptiles.--The loggerhead turtle, previously discussed,

is the only marine reptile that is common on the Georgia

coast., Green and Ridley's turtles have been reported from

coastal Georgia (see Appendix 2)

Marine mammals.--Information on mari ne mammals of

Georgia.coastal waters is restricted maihly to stranding

records and associated data. only six species of whales, all

toothed (Odontoceti), are recorded as having stranded on the

island beaches, although sight observations and strandings

from adjacent states indicate.that about 23 species are

probably components of Georgia's offshore fauna.

Atlantic bottle-nosed dolphins are probably the most

common whales in the waters immediately adjacent to the

coast. They are observed, frequently in pairs, swimming off

270

tIze beaches and tidal rivers. Stranding dates are confined

to the last half of the year, although the dolphin is

com.monly sighted throughout the year.

The pilot whale, also common, occasi mally strands

in large numbers on the island beaches. Between 15 and.25

stranded on St. Simons Island in 1962, and 53 stranded on

Little St. Simons in 1968 (Caldwell et al. 1971). Thereis,

as yet, no satisfactory explanation for these mass strandings.

Occasionally other- whales such as the rare goose-

beaked whale (with less than 20 known specimens from the

western North Atlantic--Moore 1963) strand on the coast or

are observed in the offshore waters. To date n6 baleen

w1hales (Mystic eti) have stranded-in Georgia.

The manatee occasionally is sighted or collected

on the coast (Tomkins 1956,'1958), but its status as a

permanent resident is doubtful.

Man-inadvertently has introduced the California sea

lion into the coastal waters of the southeastern United

States, and sight observations (Caldwell et al. 1971)

the presence of the species off Sapelo Island.

Specific records of marine mammals in Georgia are

given in Appendix 5.

Invertebrates

Most studies of estuarine invertebrates have dealt

117ith those forms relating in a basic way to the estuarine
fOOd chain (plankton) and with species. having commercial

271

TABLE 14. EPIFAUNA COLLECTED FROM DOCKS AT COLONELS
ISLAND (NORTH NEWPORT RIVER, ST. CATHERINES SOUND)*

Phylum Cnidaria
Unidentified anemone
Unidentified hydroid

Phylum Ectoprocta
Anguinella palmata
Alcyonidium sp.
Amathia distancs
Conopium tenuissimum

Phylum Annelida
Class Polychaeta
Nereis (Neanthes) succenea
polydora sp.

Phylum Arthropoda
Class Pycnogonida
Tanystylum orbiculare

Class Crustacea
Subclass Copepoda
Doropygus laticonis

Order Thoracica
Balanus eberneus

Order Amphipoda
Amphithoe valida
Corophium simile
Gammarus mucronatus
Lumbos websteri
Mellita appendiclata
Paracaprella tenuis
Parapleustes n. sp.

Order Decapoda
Paleomonetas vulgaris
Paleomonetas pugio
Eurypanopeus cepressus
Panopeus herbstii

Phylum Chordata
Subphylum Urochordata
Molgula manhattensis

Heard and Heard 1970.
272

a listing of those species that were,considered common or

abundant by the investigators in at least one monthly sample.

Benthic epifauna and infauna were sampled within the sounds

using a 20-foot otter trawl and'a.bucket dredge. One

hundred and eighty-five genera or forms were reported. Of

these, 79 were considered common by the authors in at least

one sample. These species are listed in Table 15.

Classification or higher taxa have been changed in Tables

14 and 15 to agree with those of Meglitsch (1967). The

restricted sample area and the selection by the colledting

devices for certain invertebrates contributed some bias to

the lists.

Most invertebrates of commercial importance (e.g.

crabs, oysters and shrimp) have been extensively studied.

Following is a brief discussion of blue crabs, oysters and

.brown and white shrimp.

Studies by Durant (1970) indicate that in Georgia

oysters (Crassostrea virginica) begin to spawn when the

temperature is about 73*F. Spawning was observed to begin

An May and to continue until October, with peak periods in

July, August ahd September (ibid.). Larval stages last for

2 to 3 weeks (Wallace 1-966), after which the young attach to

some substrate. Galtsoff (1964) states that only soft mud

and shifting sand are totally unsuitable. However, oysters

may convert a mud bottom to a more suitable habitat if a few

settle on a hard object and themselves become objects of

273

TABLE 15. INVERTEBRATE FAUNA OF SAPELO AND
ST. CATHERINES SOUNDS*-

Phylum Porifera
Halichondria sp.
Fi'crociona prolifera

Phylum Cnidaria
Leptogorgia virgulata
Renilla reniformis

Phylum Nemertina
Bicolored.form,

Phylum Phoronida
Unidentified species

Phylum Ectoprocta
Aeverrillia setigera
Alcyonidium verrilli
Amathia distans
Tn-guinelia paimata
Bowerbankia gracilis
Bugula neritina
Membrani2ora arborescens
enuis
Schizoporella unioornis

Phylum Mollusca
Class Gastropoda
Anachis avara
Busycon canaliculatum.
Busycon carica
Cerithiopsis emersoni (C. subulata)
Crepidula plana
Doridella burchi
Eupleura caudata
Mitrella lunata
Nassarius vibex
Polinices duplicatus
PyrogocTthana (tiangelia) plicosa
Terebra dislocata
Turbonilla (Pyrgiscus) interrupta

274

TABLE 15. (Continued)

Class Pelecypoda
Abra aeqgualis
Amygdalum papyria
Barnea truncata
Ensis directus
Lyonsia hyalina
Mulinia lateralis
Musculus lateralis
Mya arenaria
Solan viridus
Spisula solidissima
Tagelus divisus
Tellina agilis

Class Cephalopoda
Lolliguncula brevis

Phylum Annelida
Class Polychaeta
Arabella iricolor
Clymenella torquata
Diopatra cuprea
Glycera americana
Harmothoe-Lepidonotus app
Hydroides dianthus
Lumbrineris tenuis
Marphysa sanguinea
Nereis (Neanthes) succinea
Notomastis sp. (spp.?)
Parapironospio pinnata
Pectinaria sp. (gouldii?)
Sabella microphthalma
Sabellaria vulgaris
Sabellaria sp. (floridensis)
Sabellides sp. (oculatus?)
Scoloplos-Orbinia spp.
Spiochaetopterus oculatus
Sthenelais boa

Phylum Arthropoda
Class Pycnogonida
Anoplodactylus sp.

Class Decapoda
Acetes americanus carolinae
Alpheus normanni.
Eurceramus praelongus

275

TKBLE 15. (Continued)

Latreutes parvulus
Lysmata wurdemanni
Pagurus longicarpus
Pagurus pollicaris
Palaemonetas pugio
Palaemonetas vulgaris
Penaeus aztecus
Penaeus setiferus
Periclimenes longicaudatus
Trachypenaeus constrictus
Upogobia affinis

Phylum Echinodermata
Class Asteroidea
Asterias forbesi
Luidia clathrata

Class Ophiuroidea
Hemipholis elongata
Ophiothrix angulata

Phylum Chordata
Subphylum Urochordata
Mogula manhattensis

*Heard and Heard 1970.

attachment. Galtsoff describes the soft mud bottom of the

South Atlantic as being only marginally suitable for oysters.

He further states that oysters-need a free exchange of

water, salinities of 5 to 30 per cent and temperatures from

34*F to 86*F. Conditions are ideal for feeding when the

water, free of pollution and containing a low concentration

of small diatoms and dinoflagellates, moves over the bottom

in a nonturbulent flow.

The negative factors influencing oyster production

are described by Wallace (1966) as "pollution, predators,

and people." He reports that oyster production is inversely

proportional to human population growth in New England and

the mid-Atlantic states. Only in the southeastern and Gulf

states does oyster production even approach that of twenty

years ago. Wallace (1966) concludes that pollution is the

primary cause of the decline of the oyster industry. Sewage

is detrimental because it covers the bottom with sludge

that-smothers oysters and reduces oxygen (Galtsoff 1964).

When Escherichia coli, bacteria associated with fecal

matter and used as an index for pollution, reach certain

numbers, the oyster grounds are closed for health reasons.

Figures 35a-h (Appendix (5) show areas closed to oyster

gathering by the Georgia Department of Public Health as of

1970. Industrial wastes also affect oysters. Galtsoff

(1964) reports that red liquor and black liquor, both wastes

from pulp mills, reduce the length of time the oyster shell

277

remains open, thereby reducing the time available for

feeding. Butler*(1966) found that shell deposition is

decreased in the presence of chlorinated hydrocarbon insecti-

cides (e.g. PDT.) at concentrations as low'as 10 parts per

billion. oysters are especially susceptible to polllution

bepause of their.stationarymo&@ of'existence and their

ability to concentrate pollutants in their tissues.

Predators include flatworms, mollusks, echinoderms,

crustaceans, fish,-birds, and mammals (Galtsoff 1964).

The predominant species of marine shrimp occurring in

Georgia waters are the white shrimp (Penaeus setiferus) and

the brown shrim (P. aztecus), both of which are important

commercially. The life cycles of white and brown shrimp are

basically similar. The bottom-dwelling (benthic) adults

release their eggs freely into the waters offshore. Within

a short time, the eggs hatch into planktonic larvae. After

passing through several intermediate stages, the young

shrimp (postlarvae) move into the estuary and adopt a benthic

existence (Anderson 1955). After very rapid growth, they

assume the adult form. Marking studies indicate that after

migrating offshore the shrimp do not move into deep water

but-make.seasonal migrations parallel to the shoreline

(Anderson 1955). White shrimp penetrate the estuary to a

grea ter degree, arrive later and stay for a longer period of

time than the browns.

Salinity optima for young P"enaeid shrimp is in the

,278

range of 5 to 20 per cent, although they can tolerate

salinities from 1 to 60 per cent (Kutkuhn 1966). A complex

interaction of factors including circulation, temperature,

salinity, and fertility of waters, and type of vegetatidn

and substratum determines distribution, survival and growth

of young shrimp (ibid.). Optimum conditions are approached

in the nursery grounds of the marsh-estuary complex.

Nichols and Keney (1963) report that the identity and

distribution of crabs of the genus Callinectes on the

southeastern coast of the United States is uncertain.

Rathbun (1930) reported two species, C. sa2idus and C.

ornatus, occurring between New Jersey and Indian River Inlet,

Florida. Lunz (1958) found that only 30 per cent of the

crabs caught by trawlers in South Carolina were C. sapidus.

The two species are not recognized as such by fishermen and

are combined as blue crabs in catch data reported for

coastal Georgia.

Van Engel (1958) reports that in the Ch esapeake, Bay

area Callinectes sapidus begins mating early in May and

continues into October. Females probably mate only once,

at the time of the last molt. Sperm live in the female

receptacles.for at least a year and may be used as often as
the. female spawns (two or more times). The females migrate

to saltier waters after mating, some passing out of the bay
and into the ocean. Spawn ing is delayed at least two months
after mating-. 'When laid, the eggs are attached to the

279

abdomen of the female where they remain about two weeks

until hatching. Van Engle (1958) reports that there are two

larval stages, four or five zoeal stages, and the megalops.

These stages are passed through in about one month, after

which the first crab stage is reached. Costlow and Bookout

(1959) observed seven zoeal stages in laboratory-reared

animals. Nichols and Keney (1963), based on the occurrence

of early stage larvae, believe that spawning occurs through-

out the year. Peak numbers of first stage larvae were found

in Georgia waters during July,-August and September, and

large numbers of first and second stage zoeae were found

near the beaches with progression to advanced 'stage zoeae

20 to 40 miles offshore. Van Engle (1958) reported that

early in August many crabs reach the "first crab" stage and

begin migrating into waters of lower salinity. Male crabs

remain in less saline waters year round.

Thus blue crabs are a part of both the benthic and

planktonic communities, and they use both inshore and

offshore waters.

Fishery Resources of Estuaries and Inshore Waters

The estuarine and inshore waters, of Georgia support a

moderate-sized commercial fishery. The commercial harvest

of fish and shellfish for the period 1960-65 averaged 21.4

million pounds valued at approximately $3.4 million (Carley

1968). The catch accounted for about 15 per cent,by weight

and 17.6 per cent by value of the harvest of the South

:280

Atlantic states. The commercial harvest of fish and

shellfish has fluctuated considerably over a period of years,

but total monetary value of the catch has been relatively

stable because of increasing prices.

The shrimp fishery is the most important commercial

fishery in Georgia, accounting for 83 per cent of the harvest

value (Carley 1968). Blue crabs account for one-half to

three-fifths of the pounds of the annual harvest but account

for less than 10 per cent of the harvest value (ibid.).

Oysters average about one per cent of the total catch. Shad

are the most important fish in the'catch and, with other

fish species, make up approximately five per cent of the

total catch (ibid.).

Shrimp are harvested on the Georgia coast by trawling

during the six-month season from June 1 - December 31. The

area open to harvest extends from the mouth of the sounds to

3 miles offshore. Shrimping outside the 3-mile limit is

legal throughout the year. White shrimp dominate the catch

until late in July when they are replaced by the brown

shrimp. The browns then dominate the catch. until they are

again replaced by white shrimp late'in August. The catch of

white shrimp increases until it p.eaks in October. T.he total

catch normally consists of two-thirds white shrimp and one-

third brown shrimp (Carley and Frisbie 1968a).

Trawling is legal in Georgia during the daytime only.

This regulation is a significant factor influencing the

281

composition of the total catch. The white shrimp feeds

during the day and burrows into the mud at night. Conversely,

the brown shrimp is nocturnal, burrowing-into the mud during

the day.

The pink shrimp (Penaeus duorarum), also commercially

important in some areas, occurs infrequently in the catch-in

Georgia. This shrimp has habitat requirements (relatively

clear, shallow waters with a firm bottom) that are met in

relatively few areas in Georgia waters.

Linton (1970) conducted a survey of the distribution

and abundance of oyster beds in 1966 and 1967 and found about

10,180 acres of oyster beds, almost all of them intertidal

and landward of the barrier islands. Oyster beds are better

developed in the northern portion of the state where they
It< /71C-r'@Pctud&L
occur in a band 7 to 8 miles wide (see Figures 35a-h,Appendix

6). All oysters in Georgia are taken from privately held

areas through leasing arrangements (Carley and Frisbie

1968b). The most important factors limiting production are

pollution, unsuitable substrate, and predation (ibid.).

Between one-third and one-half of the estuarine area

suitable for oyster growth is polluted (Figures 27a-h), and

the oyster beds are closed to harvest for public health

reasons (ibid.). Little effort has been made to manage

oyster beds on a long-term basis. Assuming effective

Pollution control were possible, oyster production could be

significantly increased. Oyster shells and other material

282

suitable for spat-setting could be deposited in many areas,

and raft or line culture would be feasible in many areas

(Shaw 1967).

A relatively small hard clam fishery existed in

coastal Georgia until about 1932. A recent study by Godwin

(1967) revealed in the Altamaha Sound a population of

brackish water clams (Ran5ia cuneata) that could support a

commercial fishery, but the-area is closed for shellfish

harvest because of pollution. The hard clam or quahog

(Mercenaria mercenaria) does not occur in harvestable

numbers in Georgia (ibid.).

Blue crabs are taken in greater numbers than any

other commercial species but, due to a low unit price, they

represent a small portion of the monetary value of the catch

(C arley 1968). Crabs are harvested with pots and traps and

are taken in otter trawls incidental to shrimp trawling.

Finfish have averaged about 5 per cent of the total

quantity and value of all fish and shellfish in Georgia.

Harvest by species is shown in Ta ble 16. The greatest

proportion of the catch of finfish in 1967, thirty-six per

cent of the poundage and 45 per cent of the total economic

value, was American shad (Lyles 1969). Shad are anadromous
fish, spawning in fresh water and moving into the ocean to

mature. The adults move up the rivers from January until

April. Many shrimp and crab fishermen supplement their
income by fishing for shad during this time. Young shad

283

TABLE 16. FISH WITH TOTAL LANDINGS IN GEORGIA
OF MORE THAN 1000 POUNDS PER YEAR*

Pounds

Species 1966 1967

croaker 5,100 6,000

flounder 33,500 22,000

whiting 145,400 186,700

sea bass 2,700 1,700

black drum 2,400

red drum 5,600

grouper 92,300

red snapper 54,900

weakfish 1,300

spotted sea trout 1,200 6,900

Spanish mackerel 1,300 2,000

spot 5,200 10,500

bait and animal food 127,600 203,400

hickory shad 2,000 1,300

American shad 385,900 334,100

mullet 2,000

*Lyles 1968, 1969.

284

begin to move down the rivers in July and are found in the

Atlantic by October (Godwin and Adams 1969).

Whiting made up 20 per cent of the finfish poundage

and 15 per cent of the dollar value in 1967 (Lyles 1969).

They usually are caught while trawling for slirimp. Carley

(1968) reports that there has been a downward trend in the

abundance and catch of whiting. There are three species of

whiting inhabiting the coast of Georgia Ole-,�icirrhus

americanus, M. saxatilis, and M. littoralis), but they are

not distinguished in commercial records. Menticirrhus

littoralis prefers shallows and.surf, so it is not often

caught in trawls. Both M. americanus and M. saxatilis spawn

in spring and early summer. The young of the former occur

in both offshore and inside waters, whereas those of the

latter species live in the surf. The adults of both species

are found in both inside and outside waters (Hildebrand and

Cable 1934).

Red snapper accounted for 6 per cent of the poundage

and 17 per cent of the cash value.of the 1967 catch, and

grouper accounted for 12 per cent apd 10 per cent, respec-
tively. These are by far the largest catches reported for
these two species since 19577 (Power 1959; Power and Lyles
1964; Lyles 1965, 1966, 1968, 1969). Both species are

caught with hand lines Off the live bottom and shelf edge
habitats. Red snapper are also caught.in trawls (Lyles
1965v 1969r Struhsaker 1969).

285

The total value of the commercial fishery is probably

underestimated. Carley (1968) reported that in man cases

fish caught while shrimping were given to the crew of the

vessel and were'not reported. Menhaden form the base of the

largest fishery in the United States by volume. The larvae
and juveniles.spend their first summer in the estuaries
where they grow rapidly and serve as an important food item

.fQr many carnivorous species. They move into deeper waters

in the fall where they are caught in large purse seines

(June 1961). Approximately 2000 purse-seine sets were made

in Georgia in 1959, each averaging-20-25 tons of fish (June

1961): a total of 40,000 tons. Because there are no

menhaden processing plants in Georgia, these fish were

landed outside the state, probably at Fernandina Beach,

Florida, and are not listed in the Georgia landings.

Sport fishing is also an important element in the

coastal economy. Expenditures by an estimated 281,400 salt

water Sport fishermen on the Georgia coast totaled

$22,523,280 in 1968 (Cheatum et al. 1968). Table 17 lists

the sport fish most commonly caught on the Georgia coast.

Harvest figures are not available for salt water fish taken

by sport fishermen in Georgia.

Productivity and Energy Flow

'Nutrients

The waters comprising the coastal region are actually

a solution of many inorganic and organic compounds and

286

TABLE 17. COMMON SALT WATER SPORT FISHES OF GEORGIA

Inshore species Offshore species

spotted sea trout king mackerel

red drum (channel bass) dolphin

Spanish mackerel little tuna

tarpon great barracuda

bluefish Atlantic bonita

cobia pompano

sheepshead crevalle jack

striped bass greater amberjack

American shad red grouper

southern kingfish red snapper

triple ta 41
black sea bass

southern flounder sailfish

weakfish

Atlantic croaker

spot

lop
287

other materials in suspension. The movements and

concentrations of these substances are important aspects of

Ithe ecology of the area. Elements such as carbon, nitrogen

and phosphorus are necessary for primary production and

often prove to be limiting factors. of these, phosphorus

and zinc have been studied in the Georgia coastal waters.

Phosphorus is often limiting in oceanic waters

(Raymont 1963). Pomeroy et al. (1965) found phosphorus

concentrations of 1 micromole per liter @&M/L) in Doboy

Sound. At this high concentration phosphorus was not

considered to be a factor limiting primary production.

Estuarine water of the Altamaha River contains phosphorus

in concentrations ranging from 0.05 to 4.0,*M/L, whereas the

river water has a phosphate concentration of 0.1/AM/L.

'Pomeroy et al. (1969) concluded that the estuary acts as a

"sink" since it accumulates sediments that contain organic

matter as well as many minerals. Experiments have been
conducted in which 32P was released in the headwaters of

the Duplin River (Pomeroy et al. 1969). From this work it

was determined that the sediments play an important role in

the phosphorus cycle. Phosphorus from the surface sediments,

which are in equilibrium with the water, moves into a number

of deposit feeders and from them, via excretion, back into

the water. Subsurface sediments, not in equilibrium with

the water, are the source of phosphorus for smooth cord-

grass. Bacteria within the sediments are probably

accumulating phosphorus, which is released by the bacterial

feeders (Johannes 1965). Thus, there is a separation

be.tween pathways within the salt marsh. Phosphorus in

subsurface sediments is incorporated into the cordgrass

which serves as the-principal source for insects and spiders.

Most of the cordgrass# however, dies and enters the detritus

food chain. Thomas (1966) showed that the estuarine waters,

rich in phosphorus, are flushed out into the offshore

waters and serve as a nutrient source for phytoplankton.

Zinc is a trace element required by some organisms

and often is concentrated by them. Tracer studies with
65Zn indicate that the cycle of zinc, like that of phorphorus,

is dominated by the sediments which act as a mixed-bed ion

exchanger (Pomeroy et al.. 1969). Organisms, except fiddler

crabs and oysters, take up zinc and phosphorus at much the

same rates. Oysters demonstrate a preferential-retention

of zinc, and fiddler crabs show high initial values of zin-c

activity, falling off rapidly and becoming erratic,

suggesting movements in and out of the area. Bioelimination

of zinc seems to be slow. Concentrations of zinc are, like

phosphorus, high in the Duplin River as compared to sea

water, and the same processes that concentrate phosphorus

may concentrate zinc (ibid.).

Vitamin B is a nutrient essential for growth by
12
many organisms such as bacteria, algae and protozoa. It is

synthesized mainly by bacteria and fungi (Burkholder and

289

Burkholder 1956) and is found in large quantities in marine

invertebrates and fish. Starr (1956) and Burkholder and

Burkholder (195.6) studied the distribution of this vitamin

in suspended solids and marsh muds from the Georgia coast.

Burkholder and Burkholder.(1956) found that the dark-water
rivers contained high concentrations of B 12 per un.@t of
suspended particles. Both studies showed a progressive

increase in B from offshore stations to the head of a
.12
tidal creek. However, Starr (1956) reports that ocean
waters contain detritus richer in B 12 than the more turbid
sound waters. The highest concentration of B 12 is contained

in the detritus at the headwaters of the tidal rivers.

Starr (1956) also established that detritus entering the

marsh at high tide was not as rich in B as that leaving
12
on the ebb tide. Sediment samples taken from areas devoid
of marsh were much lower in B 12 than those taken from marsh
areas; however, both were lower in B 12 than water leaving
the marsh. Starr (1956) concluded that the muds did not add

appreciable quantities of vitamin-rich detritus to the

waters. Burkholder and Burkholder, however, report that

muds treated with sulfite yield values 3.8 times higher than

untreated samples, and Starr did not men.@ion this technique

which could have changed his conclusion. more work is
needed to clarify this problem as well as the role of B 12
in productivity of the sea.

Most of the turbidity of coastal waters is caused by

290

suspended sediments, but a significant portion (18 per cent)

is caused by organic material (Odum and de la Cruz 1967).

A standing crop of 2 to 20 micrograms ash-free, dry organic

matter per liter is reported for the Georgia estuaries, a

value much greater than reported for open sea water or other

sounds and bays (ibid.). These measurements were taken at

the mouth of a small tidal creek draining a salt marsh.

Samples taken at mid-ebb tide always produced more organic

detritus than did samples taken at mid-flood tide. This

suggested that organic material is being exported from the

rizarsh. Teal (1962) also calculated a net flow of organic

material from the marsh to the estuary and beyond.

The waters of the coastal region appear to be rich in

organic materials, the two inorganic nutrients phosphorus
and zinc, and vitamin B 12* All of these are found in higher

concentrations in the salt marsh-estuary system than in the

open ocean.

Food Webs

Food webs of the estuary are not nearly as well

understood as those of the salt-marsh. Many of the

conclusions concerning the food webs of the Georgia estuaries

must be inferred from work done in other regions. The

estuarine environment is more complex than the marsh system,

and many estuarine species migrate seasonally. Estuarine

inhabitants can be categorized as plankton, benthic infauna,

ePifauna or fouling organisms, and nekt.on. Some are deposit

feeders, some suspension feeders, and some are carnivores.

Specific food habits studies have been conducted on

commercially important invertebrates such as crabs, shrimp

and oysters. Shrimp are deposit feeders; Darnell (1958)

3-eports that detritus and fine organic material composed 58

per cent of the food of shrimp examined, and,mollusks 12 per

cent. He suggested that both young and mature white shrimp

are omnivorous, feeding largely on detritus. Oysters are

suspension feeders. Galtsoff (1964) studied ciliary

currents produced by oysters and concluded that -the food-

sorting mechanism is designed for continuous feeding in low

-concentrations and that food selection, except on the basis

Of size, is open to question. The blue crab is both a

scavenger and a predator; foods include mollusks, detritus,

crabs (Callinectes, Rithropanopeus, and unidentified

species), vegetation, and fish remains (Darnell 1958).

Data from published studies of the stomach contents

of fish (Table 18) are summarized in Table 19 to show

generalized feeding habits of estuarine fishes. Food items

are divided into the following general types: detritus,

algae, zooplankton, microbenthic invertebrates, macrobenthic

invertebrates, shrimp, and fish. The majority of fish

consume more than one type of food and are not confined to

one trophic level. Ninety-two per cent of the fish fed to

SOMG extent on benthic invertebrates. These percentages are
based only on those common species which have been studied,

C"
d2%-,&.

TABLE 18. S014E FOOD HABITS STUDIES OF COMMON
@STUARINE FISHES

Species Reference

Sphyrna tiburo (bonnethead) Gunter 1945

Lepisosteus osseus (longnose gar) Goodyear 1967

Megalops atlantica (tarpon) Rickards 1968

Bevoortia sp. (menhaden) June 1961

Anchoa mitchilli (anchovy) Darnell 1958

Galeichthys felis (sea catfish) Darnell 1958

Opsanus tau (oyster toadfish'.) Schwartz and Ducher 1963

Pomatomus saltatrix (bluefish) Grant 1962

Orthopristis chrysopterus (pigfish) Hildebrand and Cable 1934

Archosargus probatocephalus Gunter 1945
(sheepshead)

Lagodon rhomboides (pinfish) Darnell 1958

Bairdiella. chrysura (silver pprch) Darnell 1958

Cynoscion nebulosus Darnell 1958
(spotted sea ti@-out)

Cynoscion regalis (weakfish) Hildebrand and Cable 1934

Leiostomus: xanthurus (spot) Darnell 1958

Menticirrhus americanus Gunter 1945
(southern kingfish)

Menticirrhus littoralis Gunter 1945
(Gulf kingfish)

Menticirrhus saxatilis Welsh and Breder 1923
(northern kingfish)

Micropogon undulatus Darnell 1958
(Atlali-tic croaker)

Pogonias cromis (black drum) Welsh and Breder 1923

293

TABLE 18. (Continued)

Sciaenops ocellata (red drum). Darnell 1958

Stellifer lanceolatus (star drum) Welsh and Breder 1923

Mugil cephalus (striped mullet) Darnell 1958

Daralichthys lethostigma Darnell 1958
(southern flounder)

Chilomycterus schoepfi Gunter 1945
(striped burrfish)

294

TABLE 19. FEEDING HABITS OF ESTUARINE FISHES*

Type feeder Per cent of species studied

planktonic feeders only 4

Benthic feeders only 32

Fish feeders exclusively 8

Detritus feeders only 0

Plankton feeders 44

Benthic feeders 92

Fish feeders 52

Detritus feeders 16

Strict herbivores 0

Strict carnivores 34

Shrimp feeders 52

Limited to one type food 28

Eat more than one type food 72

Eat more than two types of food 52

Eat more than three types of food 32

Eat more than four types of food 12

*Summarized from data reported from studies listed in
Table 18.

295

and the data were collected with varying degrees of

precision from widely scattered areas. Some of the studies

took the age of the fish into account; others did not.

However, in every case where stomach analyses were done for

individual size classes, a change of food habits was

correlated with a change in size. For example, croaker less

than 25 mm in length eat principally zooplankton; those 25-

50 mm feed mostly on microbenthic invertebrates. Detritus,

shrimp and macrobenthic invertebrates are the main food

items of fish 50-200 mm. Large croaker (greater than 200

mm) eat macrobenthic invertebrates, shrimp and fish

(Darnell 1958) .

296

BIBLIOGRAPHY FROM
AN ECOLOGICAL SURVEY OF THE GEORGIA COAST

Literature Cited

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320

ACKNOWLEDGMENTS

Graphic Assistance: Nancy E. McNiel, Assistant Planner

Typist: Patricia N. Adger

..,,otographs: Lillian F. Dean

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