Statewide assessment of propeller damage to seagrass final report

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

STA TEWDE ASSESSMENT
OF
PROPELLER DAMAGE TO SEAGRASS

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A Report't Ith; Florida Department of Conamunity Affairs Pursuant to National
'd Atmospheric Administration Award No. NA176ZO.301
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STATEWIDE ASSESSMENT OF PROPELLER DAMAGE TO SEAGRASS

FINAL REPORT

Frank J. Sargent, William B. Sargent, Curtis R. Kruer,
Henry A. Norris, James H. Poehlman, Timothy J. Leary,
and Kenneth D. Haddad

March, 1993
Ile)

Department of Natural Resources
Division of Marine Resources
Florida Marine Research Institute

A report to the Florida Department of Community Affairs pursuant to National
Oceanic 'and Atmospheric Administration Award No. NA170ZO501.

1993
March
State-wide Assessment of Propeller Damage to Seagrass (Florida)
F. Sargent, B. Sargent, C. Kruer, H. Norris, J. Poehlman,

T. Leary, and K.HaddAd CM-

cm 315
Florida Department of Natural Resources 11.
Florida Marine Research Institute
100 8th Avenue SE () NA170ZO501
St. Petersburg, FL 33701

12. Sponsoring Organization Name and Address
U S. Dept. of Commerce/NOAA FL Dept. of Community Affairs
OCRM Final
2740 Centerview Drive
1825 Connecticut A., N.W. Tallahassee, FL32399
Washington D.C. 20235

Abstract(Limit 200 words)

Seagrasses are a vital component of Florida's coastal ecology And economy. The uninformed
and negligent operation of powerboats in waters much shallower than they were designed to operAte
is severely damaging seagrass beds throughout the state. The negative impacts of this threat are
increasing as Florida's population of coastal residents and seasonal visitors increases.
This project identifies and quantifies areas of' damaged seagrass beds throughout the state,
For the first time, the state-wide magnitude of this problem is scientifically documented. High
damage site were identified and specific actions needed for corrective measures were suggested.
T information acquired from this survey has been incorporated into the Marine Resources
Geographic Information System for analyses and effective dissemination of information to resource,
managers and appropriate regional and county goverments.
Recognizing the value of having the extent and spatial distribution of propeller damage
information, the Florida Department of Natural Resources has committed to develop, test, and
implement a state-wide management plan for propeller damage to seagrass during the next two
years. This Coastal Zone Management Program funded study is serving as the foundation for
development of the state-wide management plan and is guiding implementation of the management
plan. The management effort involves heavy interaction with local governments.

CoaStal zone management/ marine resource management seagrass boating activity
boat propeller damage

Unclassified

State-wide Assessment of Propeller Damage to Seagrass

A report to the Florida Department of Community Affairs
pursuant to
National Oceanic and Atmospheric Administration
Award No. NA170ZO501

Submitted by
Florida Department of Natural Resources
Florida Marine Research Institute

March 31, 1993

EXECUTIVE SUNEWARY

Seagrasses are a vital component of Florida's coastal ecology and economy. The
uninformed and negligent operation of powerboats in waters much shallower than they were
designed to operate is severely damaging seagrass beds throughout the state. The negative
impacts of this threat are increasing at an alarming rate as Florida's population of coastal
residents and seasonal visitors increases. The needless destruction of shallow seagrass beds
through boating activities can be avoided without imposing undue hardships on the boating
public.

This project identifies and quantifies areas of damaged seagrass beds throughout the entire
state. For the first time, the state-wide magnitude of this problem is scientifically documented.
High damage sites were identified and specific actions needed for corrective measures were
recommended. The information acquired from this survey has been incorporated into a
geographic information system for analyses and effective dissemination to DNR resource
managers and appropriate regional and county governments.

Recognizing the value of having the extent and spatial distribution of propeller damage
information, the Department of Natural Resources has committed resources to develop, test, and
implement a state-wide management plan for propeller damage to seagrass during the next two
years. The Coastal Zone Management Program funded, study) is serving as the foundation for
development of a state-wide management plan and is guiding the implementation of the,
management plan. Site specific corrective measures have been identified by this study and are
currently being put into action. The management effort involves heavy interaction with local
governments.

@INTRODUCTION

Seagrasses are a vital component of Florida's coastal ecology and economy. As the
population of the state grows, threats to the health and existence of these priceless ecological
communities also increase. Several of these threats (dredge and fill, construction of docks in
shallow waters, water pollution) are now being brought under control by an organized network
of federal, state, and local resource management programs. However there still exists one major
threat which is poorly understood by resource managers and public planners and as such is not
being regulated on a consistent basis throughout the state.

Nearly all seagrass beds in Florida show some signs of needless damage caused by boat
propellers digging trenches across these submerged wetlands. Many seagrass beds contain areas
which are completely denuded of all vegetation by intense and repeated boating activity in
inappropriate locations. Although this threat has existed since the introduction of motorized
boats, the negative impacts of this threat are increasing at an alarming rate as Florida's
population of coastal residents and seasonal visitors increases.

The needless destruction of shaflow seagrass beds through boating activities can be
avoided without imposing undue hardships on the boating public. Several preliminary
management practices targeted at alleviating unnecessary boating damage to seagrass beds have
been implemented in isolated cases. This project identifies and quantifies damaged seagrass beds
throughout the entire state. Specific types of boating activities or navigational circumstances
leading to seagrass damage are identified and discussed. For the first time, the state-wide
magnitude of this problem is scientifically documented.

A general assessment to obtain an idea of how prevalent and substantial the impact of
boat propeller scar damage is throughout the state of Florida was initiated by the Florida Marine
Research Institute's (FMRI) Coastal and Marine Resource Assessment (CAMRA) section. Using
a combination of aerial photography and aerial surveys, propeller scar damage in seagrass beds
was mapped on National Oceanic and Atmospheric Administration (NOAA) nautical charts. The
resultant information was stored in a digital format in the Marine Resources. Geographic
Information System (MRGIS) of the FMRI for data analysis and distribution to appropriate
federal, state, and local agencies.

Due to both the complexity and the expansiveness of seagrass communities in the Florida
Keys, a local consultant with extensive experience was subcontracted to conduct the Monroe
County portion of this project. The contractor's data and findings are incorporated into this
report as appropriate. The contractors full report is included as Appendix A.

DISCUSSION OF THE PROBLEM

The importance of seagrasses as a natural resource is well documented from extensive
research in the last thirty plus years (Dur@ako, et al., 1987). Seagrass communities are
recognized as a vital link in near shore benthic resources and are also considered to be one the
most productive ecosystems in existence (Dawes, 1987; Zieman and Zieman, 1989). Zieman
and Zieman (1989) produced a conceptual framework which appropriately illustrate the
importance of seagrasses: 1. High production and growth - Seagrasses yield high net
productivity. 2.. Food and feeding pathways - Grazing of the seagrasses and detrital material
both in place and in movement to other locations. 3. Shelter - Seagrasses are a primary nursery
for finfish and shellfish. 4. Habitat Stabilization - The stabilization of sediment with the root
systems and reduction of particle suspension near substrate water interface. 5. Nutrient effect -
The provision of organic matter by decay and the uptake and release of nutrients into the water
column.

The recovery of seagrasses from impacts such as propeller scar damage has been studied
in recent years (Godcharles, 1971; Zieman 1976) and research continues to take place as the
problem of propeller scar damage to seagrasses appears to be growing eg. Durako et al., 1992
and currently Clinton Dawes Ph.D. According to Dawes (pers. comm.) of the University of
.South Florida, the program at the Cockroach Bay Aquatic Preserve began in January of 1993
and is a two year study involving the recovery of seagrasses in old scar and new scars created
for the study. This type of research enables us to better understand the ramifications of
propeller scar damage to the seagrasses and time frames for recovery.

Initial research by Zieman (1976) indicated Thallasia_ testudinm may require at least two
years before recolonization begins. Even after five years some propeller scars had not recovered
from being damaged. His study also stated that Halodule wrightii recovers much quicker than
does the T. testudinum. Durako's (et. al. 1992) research documented that H. wrighti would only
require 0.9 - 1.8 years to regain their natural densities and T. testudinum would take
approximately 3.6 - 6.4 years to achieve' natural short shoot densities. Some research has
indicated, that dependent on the size of a seagrass bed complete recovery may take ten years
(Lewis and Estevez, 1988).

Seagrass recovery is dependent on several factors for regrowth; sediment composition
(eg. Florida Bay vs. Tampa Bay), position of the propeller scar with regard to water current
(flow) and depth (Godcharles, 1971; Zieman, 1976; Durako, et al. 1992). Zieman (1976)
indicated that propeller scars may not fill in with sediment if located in areas of extreme current.
From this condition, the severed rhizomes may grow up or down the side of the propeller scar
but were not seen to cross over it. Durako (et al., 1992) explains, how the sediment environment
of south Florida with predominately carbonate sediments, would exhibit a different regrowth
period for the'seagrasses in propeller scars than the prop damaged seagrasses, of Tampa Bay,
which inhabit a quartz-sand sediment environment. The depth of the scar is also a contributing
factor to regrowth of propeller scar damaged seagrass, bed. Studies involving trenches or
excavations cut into seagrass beds of 6 inches to 18 inches deep were very slow to recovery

(Zieman, 1976 and Godcharles, 1971). The trenches-excavations filled in readily, although
regrowth was slow even after two years.

Over the years there have been various impacts have reduced the areal extent of
seagrasses of Florida including dredge and fill, water pollution, and boat propeller damage. A
dominant benthic ecosystem in the state, seagrasses offers a wide variety of benefits ranging
from habitat, nursery and its link in the food chain (Zieman and Zieman, 1989). Damage to
seagrass beds by boat propell ers was noted as early as the 1950's and 1960's (Woodburn, 1957;
Phillips, 1960) and has steadily become a significant impact. Damage to seagrasses from boat
propellers results from one or more of the following combinations; boaters misjudging water
depth, taking short cuts, commercial fishing, recreational boating, recreational fishing, and
intentional propeller dredging to create a channel (Woodburn, et al., 1957; . Godcharles, 1971;
Zieman and Zieman, 1989; The Wilderness Society et al. 1990). Damage may consist of an
isolated boat propeller scar or a series of boat propeller scars which have defoliated portions of
the seagrass beds leaving an area which may be completely void of seagrasses or other plants.

In addition to the current research of damaged seagrass beds, resource managers have
already established management programs for Weedon Island Sate Preserve, Cockroach Bay
Aquatic Preserve (TBRPC, 1993), and John Pennecarnp Coral Reef State Park. Other counties
and state agencies are also adopting similar programs. Any combination of the management
programs may be implemented; monitoring of propeller scar damage using aerial photography,
better channel marking to aid boaters, closure of specific areas to combustion engines and/or
boater education as a means of reducing the amount of propeller scarring in seagrass beds.

REPORT DEFICIEENCY

At the time this report was produced two areas in Florida had not been mapped due to
poor water clarity, poor weather conditions, and scheduling and logistics problems. A small
portion. of Monroe county and a majority of the Florida panhandle remain to be surveyed.
Ancillary information for these areas have been collected and reviewed and contracts are in place
to complete the aerial surveys. These two areas represent a small percentage of the seagrass
regions in the state and do not detract from the' immediate application of the information
contained in this document,

All maps, tables, and findings published in this report are preliminary. The information
contained in this report is in draft status and must be used accordingly. A refined and completed
survey result is currently being developed as part of a follow through management effort being
developed by DNR as a result of this Coastal Management Program funded project. The DNR
management initiative is a logical expansion of Task 3 of this Coastal Management Program
funded project and is explained in detail in that section of this report.

Task I Statewide assessment of propeller damage.

Aerial photographs were utilized to reconnoiter the distribution and magnitude of
propeller damage to seagrass throughout, Florida's shallow coastal waters. The most recent
photographs of sufficient quality to identify propeller scars were used. Due to the fact that no
comprehensive state-wide effort exists to inventory and assess benthic resources, the photographs
were of various quality, scales, and media types. Photographs for localities not covered by
FMRI's aerial photograph library were obtained or borrowed from the water management
districts. Although a few gaps in coverage did exist, for the most part the photography was
extremely useful in conducting a preliminary assessment and planning an efficient ground
truthing strategy.

For most regions of the state 9 inch by 9 inch color infrared (CIR) transparencies at a
scale of 1:24,000 were used. The best photographs available were 1: 12,000 CIR transparencies
taken in December 1991 for the Florida Marine Research Institute's Florida Keys benthic
mapping project. Southwest Florida Water Management District supplied 1:24,000 CIR
photographs for Tampa Bay and south to Charlotte Harbor. St. Johns River Water Management
District supplied 1:24,000 CIR photographs for Mosquito Lagoon and Indian River Lagoon. The
South Florida Water Management allowed use of 1:40,000 CIR transparencies for Hobe Sound,
southeast Florida, Biscayne Bay, parts of the Keys and Florida Bay, southwest Florida, and
portions of Charlotte Harbor. Photography of submerged aquatic vegetation for the panhandle
and Big Bend regions was to have been taken as part of the EPA/USFWS Gulf of Mexico
seagrass mapping project, but bad weather and poor water clarity had delayed'this effort and no
photographs were available.

Interpretation of the 1:40,000 scale photographs did not pose any major difficulties due
to excellent through the water visibility of these regions and the fine quality of the photographs.
A previous Florida Marine Research Institute study (Durako, et al, 1992) suggested that the
smallest scale (least detailed) aerial photography appropriate for interpreting propeller scars for
general assessment was 1:24,000. This was found to be true for regions of the state with less
than optimum water clarity. Fortunately 1:24,000 scale photographs were available for most of
those areas.

The oldest photographs utilized were taken in Novemb er 1990. Although two year old
photographs did not represent current conditions, they did document patterns of past propeller
damage and indicated hot spots which required closer examination. Even the most recent
photographs were used only for preliminary assessment.

Magnifying scopes and stereoscopes designed for interpretation of aerial photographs
were used to.identify and delineate propeller scars observed in the photographs,. This allowed
the extraction of as much data as possible from the photographs. Delineations and registration
marks were drawn on acetate overlays which were then used to transfer the information to
nautical charts.

Damage was de 'fined as scars across the seagrass bed from which shoots and rhizomes
had been removed and the bottom sediment was visible. These scars were visible in photographs
and from the air as sharp lines with a distinct contrast in shade tone from the seagrass. Scars
typically appeared similar to those visible in the cover photograph of this report. Mapping of
individual scars was beyond the scope of this state-wide survey and perhaps impossible at any
level of detail. There were just too many scars and at most locations the scars were so numerous
that they could not be distinguished individually. Where several scars were observed within
close proximity a polygon was'drawn around the scarred area. Mapping of areas less than one
acre was not appropriate due to the scales involved.

An estimate of the degree of damage was then assigned to the polygon. Light impact
indicated that.damage was present but that less than 5% of the seagrass within the delineated
area was directly impacted. Moderate impact indicated 5-20% of the seagrass was impacted and
severe impact indicated more than 20% of the seagrass within the area was impacted. For
example, 100 acres of seagrass classified as moderately impacted could contain between 5 and
20 acres of actual propeller scars. A "Comparison Chart for Visual Estimation of Percentage
Composition" (Terry and Challenger, 1966) was used to guide estimation of damage. Figure I
presents a graphical representation of the three levels of estimated damage. The seagrass bed in
the cover photograph was assigned a damage level of severe.

In many instances a wide variety of damage levels occurred within close proximity, The
area was then assigned an average value of estimated damage level. A graphical example of this
situation is provided as Figure 2.

The assignment of damage levels was subjective and should only be considered in the
context of this project. For a more definitive assessment of damage, each site must be reviewed
individuAlly. Only general areas of impact were defined. This study was not designed to provide
Accurate assessments of seagrass loss on a detailed basis.

Light Damage Level Each 100 acres of seagrass contains
scars amounting to less than 5
acres.

A B

Moderate Damage Level Each 100 acres of seagrass contains
between 5 and 20 acres of scars.

I-J
C D

Severe Damage Level Each 100 acres of seagrass contains
over 20 acres of scars.

Figure 1. Graphical representation of the three levels of estimated
propeller damage identified in this project. White space within
each block represents seagrass while the black marks represent
scars. Light damage level ranges between blocks A and B, moderate
damage level ranges between blocks C and D, while severe damage
level ranges between blocks E and F.

Figure 2. An example of a polygon delineation which includes all
three types of damage; Light, moderate, and severe and categorized
(mapped) as severe.

Polygons drawn on the overlays were transferred to nautical charts with a zoom transfer
scope. The zoom transfer scope super-imposed images from a drawing onto a basemap of another
8cale. This allowed for precise transfer of the hand drawn damage polygons from the photograph
overlays onto a base map even when their scales differed. Charts of the most appropriate scale
and most recent date for each region were used. In most cases 1:40,000 charts and their
1: 10,000 insets were used. Use of charts with a smaller scale would have been too cumbersome
and required an unreasonable number of individual charts to provide state-wide coverage. In
most regions larger scale (more detailed) charts were not available for these same reasons.

National Oceanic and Atmospheric Administration (NOAA) navigational charts were
chosen as the base media for, drafting propeller damage polygons because they are suitably
accurate, appropriately detailed, provide geographical references for positioning in offshore
areas, readily available at low cost, and are used by most agencies conducting natural resource
work in coastal waters. The shorelines depicted on these charts were compatible with the Marine
Resources Geographic Information System (MRGIS) shoreline data which aided incorporation
of damage data into the MRGIS. Transfer of information from the charts into the MRGIS was
also facilitated by accurate and well distributed graticules, used for registration of geographic
position, on the charts. The individual NOAA charts used are listed in Table 1.

Table 1. NOAA nautical charts and USGS topographic maps used as base maps for the drafting
of polygons depicting propeller damage to seagrass.

Numbe Official Title

Chart 11378 1:40,000 Intracoastal Waterway Santa Rosa Sound to Dauphin
Island
Chart 11393 1:40,000 Intracoastal Waterway - Lake Wimico to East Bay
Chart 11402 1:40,000 Intracoastal Waterway - Apalachiacola to Lake Wimico
Chart 11404 1:40,000 Intracoastal Waterway - Carrabelle to Apalachicola Bay
Chart 11405 1:80,000 Apalachee Bay
Chart 11407 1:80,000 Horeshoe Point to Rocks Islands
Chart 11408 1:80,000 Crystal River to Horseshoe Point
Chart, 11409 1:80,000 Anclote Keys to Crystal River
Chart 11412 1:80,000 Tampa Bay and St. Joeseph Sound
Chart 11413 1:40,000 Tampa Bay - northern part
Chart 11414 1:40,000 Tampa Bay - southern part
Chart 11425 1-:40,000 Intracoastal Waterway - Charlotte. Harbor to Tampa Bay
Chart 11427 1:40,000 Intracoastal Waterway - Fort Myers to Charlotte Harbor
Chart 11430 1:40,000 Everglades National Park - Lostmans River to Wiggins
Pass
Chart 11432 1:50,000 Everglades National Park - Shark River to Lostmans River
Chart 11433 1:50,000 Everglades National Park - Whitewater Bay
Chart 11441 1:30,000 Key West Harbor and approaches
Chart 11442 1:80,000 Sombrero Key to Sand Key
Chart 11445. 1:40,000 Intracoastal Waterway - Bahia Honda to Key West
Chart 11448 1:40,000 Intracoastal Waterway - Big Spanish Channel to Johnson
Key
Chart 11449, 1:40,000 Matecumbe to Bahia Honda Key
Chart 11451 1:80,000 Miami to Marathon and Florida Bay
Chart 11463 1:40,000 Intracoastal Waterway - Elliot Key to Matecumbe
Chart 11465 1:40,000 Intracoastal Waterway - Miami to Elliot Key
Chart 11467 1:40,000 Intracoastal Waterway - West Palm Beach to Miami
Chart 11485 1:40,000 Intracoastal, Waterway - Tolomato River to Palm Shores
USGS map 1:24,000 Marquesas Keys West
USGS map 1:24,000 Marquesas Keys East
USGS map 1:24,000 Cottrell Key
USGS map 1:24,000 Key West

After charts were preliminarily marked with damage polygons, aerial surveys were
conducted for groundtruthing and, refinement of the delineations and damage classifications. In
some cases where seagrass beds or shorelines had complicated geometry the original aerial
photographs were brought along as ancillary data and also edited in-flight. Aerial surveys were
critical to accurate data collection since not all scarring was visible in even the best photographs.
Numerous areas of damage were added to the charts during the overflights and a more accurate
assignment of damage levels was possible.

Florida Marine Patrol aircraft and pilots were used for the aerial surveys when possible.
The local knowledge these pilots had of each region, the natural resources present, and common
boating patterns was invaluable to the project. Light fixed-wing aircraft (Cessna 172) were flown
in regions wheri'seagrass was distributed along straight and continuous shorelines. The Indian
River Lagoon and the southeast Intracoastal Waterway were surveyed from a plane. The Cessna
was found to be very economical. Regions with convoluted shorelines and numerous islands
were surveyed by helicopter (Hughes 500). Tampa Bay, Biscayne Bay, Wacassasa Bay, and
parts of Florida Bay were surveyed with a helicopter. The ability of the helicopter to maneuver
and hover improved the accuracy of the survey and also reduced time spent circling and
returning to spots of interest.

Survey altitudes between 300 and 500 feet provided the best observation perspective. At
higher altitudes scars were usually not visible and at lower altitudes too much flight time was
required to cover large areas. In a few locations were. conditions permitted, higher altitudes were
flown. Flight speeds between 80 and 100 knots were used depending on the complexity of
scarring and clarity of the water.

Good. weather and water clarity were essential for aerial surveys. Optimum conditions
were clear sldes, calm sea state, winds less than 10 mph, a high sun angle, and clear water. Rain
and high winds made seeing through the surface of the water impossible. Sun glare reflecting
off thewater in late afternoon and early morning-also hampered observations. Turbidity caused
by rough water during storms usually persisted for several days afterward. Dark colored water
discharged from organically stained rivers during and after rain storms was the major
impediment for aerial surveys. River discharge continued for many days after the large frontal
systems passed through the panhandle and Big Bend regions. Surveys were attempted during
poor conditions but it proved to be impossible to observe seagrass and scars when weather and
water conditions deteriorated past certain limits.

Photo-documentation in the form of 35mm. slides and Hi8 video was collected during the
aerial surveys. One such photograph was placed on the cover of this report. These photographic
records were placed in a photo library at the Florida Marine Research Institute and made
available to all interested parties. In a few instances this information was referred to when
drafting the final version of the propeller scar damage charts. Slides depicting damage were
provided to newspapers and a Hi8 video of damage in the Keys was provided to a local public
television station for inclusion in a documentary. Local resource managers have requested copies

of some of this photo-documentation. A marina expansion permit review and the development
of an aquatic preserve management plan have been facilitated with the use of this'photography.

During the aerial surveys, it was quite common to observe boats in the process of
creating propeller scars in shallow seagrass beds. A wide variety of examples of this activity
were captured with both the still photography and the video.

After aerial surveys for a region were completed, the damage information was edited and
recompiled onto a clean set of charts. The clean set of charts was then used in the transfer of
damage information into the Marine Resources Geographic Information System. All charts and
photograph overlays have been archived for future reference.

Task 2 Implement the resultant information on the Marine Resources Geographic
Wormation System.

Inform ation from the finalized charts was transferred into the MRGIS through manual
digitization. Plots were produced and checked against the original charts to ensure an accurate
transfer had been conducted. All positional accuracies of the final data layer fell within accepted
standards for work of this type.

ARC/INFO is the geographic information system software used by the MRGIS. This
software is used by numerous county governments, the water management districts, the
Department of Environmental Regulation, several divisions of the Department of Natural
Resources, the United States Fish and Wildlife Service, the National Oceanic and Atmospheric
Administration, the Florida Game and Fresh Water Fish Commission, Regional Planning
councils, several state universities, many private consulting companies, and utilities. The
seagrass damage information is in a digital format which can easily be shared with other
agencies which need it. The MRGIS can also incorporate various types of data generated by
,these agencies and use it for spatial analyses with the damage data. The propeller damage data
is now in a format which is extremely accessible to those who need.it and in this format it is
also ready for use in powerful spatial analyses and map production.

A great wealth of information such as boat ramps, marinas, boating traffic and densities,
navigation channels, artificial reefs, fishing grounds, manatee occurrences, coastal wetlands,
population and housing densities, and transportation networks can also'be displayed on maps
produced by the MRGIS. Relationships of propeller damage to any type of geographic
phenomena can be analyzed, displayed and turned into paper maps by the MRGIS.

Examples of paper maps which can be produced by the MRGIS are presented as Figures
3 and 4. Examples of larger maps accompany this report. All of these maps are preliminary and
are to be used as examples only. These maps were generated on a Calcomp 68436 Electrostatic
Plotter. A wide variety of sizes and formats of maps can be produced by the MRGIS.
Customized maps can be produced in only a few hours if they are not too complicated. The

ability to produce customized paper maps makes the data and results of complex analyses readily
available to anyon e who needs the information.

The estimates of damaged areas presented in Table 2 were calculated by the MRGIS.
These estimates can be instantly recalculated for the entire state or any portion thereof as new
data become available.

Figure 3. (refer to facing page) Detailed map depicting areas of seagrass containing propeller
scars at Pine Island, Charlotte county, an area nominated for management action. Note the
damaged area to the southwest (lower left) of the marina. South bound boats leaving the marina
take a short cut across the shallow seagrass beds and cut scars through the seagrass. A marked
deepwater boat channel (narrow band of blue) extends due west from the marina to open water
and the Intracoastal Waterway. This information was supplied to the regional aquatic preserve
manager and is being incorporated into a regional aquatic preserve management plan.

DETAILED PROPELLER SCAR DAMAGE
TO THE SEAGRASS AREAS OF PINE ISLAND

..........

...........

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

SCALE 1:40,000
. ...........

ET
ZILOMMRS
..........
........ ..

0 1

Seagms Community
Ao Light Damage
Moderate Damage
Severe Damage
Numbers represent the acreage
........... of seagrass areas impacted
southwest of the marina. Note,
the channel extends east to west
from the

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

Marina

Fkd& I
HW& Mh. R.-* balft
M@ R- G.Vqhw td-fi. 9"-
Ir

_JL

. . . .......

-t7

Figure 4. (refer to facing page) Areas of propeller scar damage at Windley Key, Monroe
county, an area targeted for implementation of management action to protect shallow water
seagrass habitats.

DETAILED PROPELLER SCAR DAMAGE
TO THE SEAGRASS AREAS OF WINDLEY HARBOR, FLORIDA BAY

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

INP 1111
Jlii@i...!@
.. . ..... . .. ..
. .........
..........

..........

TIEN"

Ilp]

1INT 1"
4!N

....... ...

A110

. . ...... ..

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

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

n iiE
V':::I1i.'-_1:t 4 :!IIAl
Coral Community 15 =Light Damage 50
=Bare Bottom Community 120 Area Calculations m* Acres 01MIKE Moderate Damage 181
r"27-79
Hardbottom Community 1,785 LL@j Severe Damage 2-32
Seagrass Community 12,552

Table 2. Areas of seagrass identified to have been impacted by boating activities in Florida
counties. Unit of measurement is acres. Light damage is defined as scars occurring in up to
5% of the identified area; moderate damage is scars occurring in 5% to 20% of the identified
area; heavy damage is scars occurring in more than 20% of the identified area. Counties west
of Dixie County and a small portion of Monroe County were not yet surveyed at the date this
report was compiled. These data are preliminary and subject to refinement.

COUNTY AREAS OF SEAGRASS IDENTIFIED
LIGHT MODERATE SEVERE

Brevard 4,878 2,300 15
Broward 1 0 0
Charlotte 2,251 6,117 239
Citrus 5,676 1,480 0
Collier 2,182 1,603 110
Dade 3,587 4,466 4,053
Dixie 2,605 1,105 0
Hernando 793 759 4,194
Hillsborough 3,068 7,457 453
Indian River 332 61 0
Lee 7,467 7,907 1,492
Levy 3,327 109 0
Manatee 4,485 2,719 475
Martin 22 5 0
Monroe 9,164 6,493 2,455
Palm Beach 89 36 0
Pasco 1,042 1,645 169
Pinellas 6,746 6,554 3,087
Sarasota 913 439 42
St. Lucie 45 46 0
Volusia, 1,492 1,104 382

Task 3 Develop a final report and provide the results to resources managers with site
specific recommendations for implementation of corrective measures.

The preliminary findings of this project were provided to several agencies during the
actual course of the project. Many agencies were contacted in the beginning stages of this work
and awareness of the issue created a demand for information as it was being collected. Several
newspapers have written articles on the project and the issue of propeller damage. One article
is presented in Appendix B. Miami public television station WLRM channel 2 requested some
of the aerial video for inclusion in a documentary about environmental problems in the Florida
Keys. Efforts aimed at educating the public through the news media will continue.

Specific management actions to protect the shallow water seagrasses of Windley Key,
Monroe county, have been proposed and are discussed in detail in Appendix C. A map depicting
the propeller damage around of Windley Key is provide as Figure 2. The southwest Florida
Aquatic Preserves office utilized data from this study to develop an aquatic preserve management
plan which incorporates measures to protect .seagrass from propeller damage. An area of heavy
damage in Pine Island Sound has been targeted for implementation of a management action
(Refer to Figure 1). Assistance was provided to Pinellas County, Hillsborough County, and the
Florida Park Service in the refinement of management plans for specific localities.

All these management activities are being incorporated in the Department's newly funded
initiative on seagrass propeller scar damage management and education which is discussed
below. A list of agencies which have expressed an interest in actively participating in this
initiative is provided as Appendix D.

DNR Seagrass Propeller Damage Management and Education Efforts

Through the Coastal Zone Management Program a survey of propeller damage to
seagrass has been conducted. It has taken almost 3 years from our perception that this was a
growing and state-wide problem to receiving funding and conducting the survey. During this
time-frame propeller damage to seagrass has become a state-wide issue. As a result of this
survey, propeller damage to seagrass is one of the. few coastal management issues that now
actually has information available to assess the magnitude and distribution of a problem in order
to develop sound management actions.

Recognizing the value of having the extent and spatial distribution of prop damage
information, the Department of Natural Resources has committed resources to develop, test, and
implement a state-wide management plan for propeller damage to seagrass during the next two
years. This effort involves heavy interaction with local governments. A discussion of the
Department's currently funded seagrass propeller damage management and education project as
it was proposed is provided below. The DNR project builds upon the Coastal Zone Management

Program study and some critical portions have already been fulfilled by completing this study.
Several other portions are already well underway.

A. Need

Seagrass meadows are one of Florida's most important submerged marine habitats and
are critically important to productivity in shallow water areas of the State.

As Florida's population grows, the number of boats on the water increases. Propeller
damage to seagrass beds has recently been recognized as a significant problem in Florida's
shallow waters (we estimate tens of thousands of impacted acres). Concerns are being expressed,
statewide, as public awareness to the problem grows. There exists no state-wide plan for
managing propeller damage or for educating the public on the issues. A comprehensive state to
local approach to management needs to be action oriented and tested.

B. Objective

To reduce impact of boat propellers to seagrass, thus reducing wetlands loss, through the
development and implementation of a state-wide propeller damage to seagrass management plan
that targets high resource impact areas. To develop a prototype public education instrument that
focuses on educating boaters on how to minimize propeller damage to seagrass and brings
awareness of the Management Plan to the public.

C. Expected Results or Benefits

Seagrasses are critical wetlands components of Florida's natural resources. Seagrass
meadows provide a direct food source to herbivores, such as sea turtles and manatees, and to
numerous organisms dependent on the detrital.matter they produce. Because this habitat is
subtidal and extensive in distribution, it provides a constant and expansive structural shelter for
fish and shellfish important to -the fishery and ecosystem. In addition, the complex food 'web and
tremendous organism diversity and quality provide a major, food source to all stages of many
coastal species including the endangered manatee and several sea turtles. Seagrass meadows
improve water quality by removing nutrients and by providing a baffle effect on waves and
currents, which causes settling of suspended particles in the water column.

Florida has documented losses of seagrass ranging from 81 % in Tampa Bay to 30 % in
Indian River Lagoon. These losses have been impacting estuarine. dependent species and the
overall quality of the affected ecosystems. Large scale losses have been attributed to@ dredge and
fill activities and decreases in water quality. However while these issues are being addressed,
propeller damage has been increasing due to the growing boating population and lack of a
comprehensive approach to addressing the issue and educating the boating public. It is possible
that loss of seagrasses due to propeller damage far exceeds the losses due to other factors.

This project will provide a comprehensive state-wide Management Plan, test the
implementation of the Management Plan, monitor the results of the test implementation, and
develop the consensus for state-wide implementation of the Management Plan. The results will
be a reduction in loss of seagrass habitat due to boat propeller damage. In many areas regrowth
of seagrass can be expected thus increasing the contribution of this important habitat.

D. Approach

A six step approach to accomplishing the objective is proposed.

1. Determine the magnitude and locations of propeller damage state-wide. Schedule:
This has been accomplished with completion of the Coastal Zone Management Program
funded survey.

2. Develop a comprehensive state-wide management plan that incorporates the
knowledge from the state-wide seagrass propeller damage mapping efforts (see F). The
Management Plan will include locator maps specifying the locations of,impact, and
evaluation and determination of the likely cause of impact (e.g. improperly marked or
spaced channel markers, unmarked channels, negligence by boaters.), an evaluation and
recommendation for management policy or remedial actions on either state-wide or local
levels, and an evaluation and recommendation of the agency(s) that should implement
policy (if needed) and remedial actions (e.g. increased channel marking, boater
education). This management plan will be developed in consultation with the Department
of Natural resources (Divisions of Law Enforcement, Marine Resources, Recreation and
Parks, State Lands, and General Counsel), the Office of the Governor (Office of
Planning and Budget), the Department of Environmental Regulation (Office of
Intergovernmental Affairs), the Department of Community Affairs (Coastal Zone
Management Office), and Pinellas, Dade, Sarasota and Monroe Counties (offices of
marine resources and environmental management). Schedule: A draft plan will be fully
developed by the 12th month of the project.

3. Test implementation of Management Plan recommendations in Pinellas, Dade,
Sarasota, and Monroe Counties. A management plan has no demonstrable merit without
commitment and accomplishment of actions. It will be very difficult to implement a state-
wide comprehensive plan for reducing propeller damage to seagrass without a
demonstration that recommendations can be implemented at the local level and that the
net result is a reduction of impact. The Department will contract the proper county or
other appropriate agency to facilitate implementation. Schedule: We propose to complete
the components of the Plan for the regions that include the aforementioned counties
within the first 4 months of the project and implement recommendations that cross the
spectrum of impact reduction measures included within the Plan during the first year of
the project.

4. Monitor results of the test implementation of recommendations. In order to determine

the effectiveness of the Plan, implementation sites must be monitored to determine if
propeller damage is reduced. Aerial photography and videography will be used to
document the status of propeller scars for selected sites in each county. Scars will be
documented prior to a remedial action and will be documented 12 months after that
rediedial action. This will not be a controlled experiment but a simple measure of change
in propeller scars. The Department has already conducted research to assess the methods
for monitoring propeller scar damage in a separate project. The general effectiveness of
remedial action can be determined by this cost efficient approach. Schedule: 12 months
after remedial action at a selected site. This would extend to the end of Year 2.

5. State-Wide Plan Implementation: The success of the project is dependent on
implementation of a state-wide plan that acknowledges the distributed roles and
authorities of carrying out the plan. A consensus building process will be enacted during
Year 2 to fully develop the action items of the Plan and establish the roles and authorities
of the agencies. The Interagency Management Committee (a committee that addresses
coastal management issues) will be used to provide the forum for consensus building at
the federal, state, and local level and the forum for executive implementation of the
Management Plan. Three workshops will be held to accomplish the goals. Schedule:
Completion of Year 2.

6. A certain component of the Management Plan will be education and information
distribution. We propose to develop a map series for distribution in the five test
implementation counties. Information distribution concerning boating and habitat
protection is an important factor in managing boaters for the reduction of impact to
seagrasses. Using Geographic Information System (GIS@) technologies the Department will
produce accurate and informative maps that act as a pictorial magnet for getting
information to the boater. Befits include boater access information, resource protection,
and boater education. Seagrass propeller damage and other resource cautions (e.g.
manatees) will be incorporated into the maps. We are currently producing a similar type
of informational map for Tampa Bay in cooperation with the National Estuary Program
and that would be a model for a propeller damage informational series. The opened color
brochure would be an approximate 24"x36" map on one side and information and insets
on habitat and species on the other. We also propose the prototype development of signs
that would contain the same information. Sign placement would need to be determined.
Schedule: The development and printing, the establishment of a targeted distribution
method, and distribution of the informational series would occur during Year 1.

E. Location:

The plan will be state-wide while implementation testing and development of an
informational series will occur in Pinellas, Sarasota, Dade, and Monroe Counties.

F. Relation to other projects

The Department is currently developing a state-wide assessment of propeller damage.
Using aerial photography, aerial observations, and local expert knowledge, a delineation of low
to moderate and moderate to high seagrass damage areas is being determined. The resultant
information is being implemented on the Marine Resources Geographic Information System.
Using GIS and cartographic techniques, the delineated areas of damage will be transferred from
nautical charts into the Marine Resources Geographic Information System nautical chart map
base. This provides a significant step in the development of the Management Plan. Interim
propeller damage management actions have been instituted by the Department to minimize
seagrass propeller damage in several small state managed areas in Pinellas and Monroe Counties.
The National Estuary Program has facilitated some education and signage. Pinellas County has
enacted some management actions in targeted areas. Numerous other federal, state, and local
entities have been exploring enacting various forms of propeller damage management. This
proposed project will comprehensively identify the areas to target for management and provide
the forum to manage the effort state-wide in an interagency network that currently does not
exist.

G. Flublic involvement

Public involvement is currently expressed, through concern to government agencies.
Development and distribution of the informational series will involve the public. The entire
project is based on interagency coordination and cooperation from federal to local levels as
outlined in the previous sections.

References

Baker, V. and G. Garret. 1992. Boating impacts management plan, final report. DNR contract
#C - 7442. Key West, FL

Dawes, C.J. 1987. The dynamic seagrasses of the Gulf of Mexico and the Florida coasts. Pp.
25-38 in M.J. Durako, R.C. Phillips, and R.R. Lewis III (eds.). Proceedings of the Symposium
on Subtropical-Tropical Seagrasses of the Southeastern United States. Florida Marine Research
Publication No. 42.

Durako, M.J., M.O. Hall, F Sargent, and S. Peck. 1992, In Press. Propeller scars in seagrass
beds: As assessment and experimental study of recolonization in Weedon Island State Preserve,
Florida.
in F. Webb, Proceedings from the 19th Annual Conference of Wetlands Restoration and
Creation.

Eleuterius, L. 1987. Seagrass ecology along the coasts of Alabama, Louisiana, and Mississippi.
Pp. 11-24. in M.J. Durako, R.C. Phillips, and R.R. Lewis III (eds.). Proceedings of the
Symposium on Subtropical-Tropical Seagrasses of the Southeastern United States. Florida
Marine Research Publication No. 42.

Folit, R. and J. Morris. 1992. Beds, boats, and buoys: A study in protecting seagrass beds
from motorboat propeller damage. Environmental Studies Program Publications #39. New
College of University of South Florida. 101 p.

Godcharles, 1971. A study of the effects of a commercial clam hydraulic clam dredge on benthic
communities in estuarine areas. Florida Marine Research Laboratory, Technical Series No. 64.
51 p.

Kenworthy, W.J., S. Fonseca, and G.W. Thayer. 1988 A comparison of wind-wave and boat
wake-wave energy in Hobe Sound: Implications for seagrass growth. Ann. Rep. to U.S. Fish
and Wildlife Service Sirenia Project, Gainesville, FL. 21p.

Lewis, R.R.,111 and E. Estevez. 1988. The ecology of Tampa Bay, Florida: An estuarine
profile. U.S. Fish and Wildlife Service Biol. Rep.85(7.18). 132 p.

Livingston, R.J. 1987. Historic trends of human impacts on seagrass; meadows-in Florida. Pp.
139-151 in M.J. Durako, R.C. Phillips, and R.R. Lewis III (eds.). Proceedings of the
Symposium on Subtropical-Tropical Seagrasses of the Southeastern United States. Florida
Marine Research Publication No. 42.

Phillips, R.C. 1960. Observations on the ecology and distribution of the Florida seagrasses.
Florida State Board of Conservation Marine Laboratory, Professional Papers Series, Number
Two. 72 p.

Matthews, T.R., A.C. I.Am, and J.H. Hunt. 1991. Aerial observations of boating impacts to
shallow water grass beds in the Florida Keys. Rep. to Fla. Dep. Nat. Resour., Office of Marine
Programs and Planning. I I p.

Richard, J. 1992. Texas seagrass beds and boat propellers. Pp. 11-12. in Tide, Coastal
Conservation Association. Houston, TX.
Tampa Bay Regional Planning Council (TBRPC). 1993. State of Tampa Bay 1992-1993.
Agency on Bay Management. 63 p.

Terry, R.D. and G.V. Challenger. 1966. Comparison charts for visual estimation of percent
composition. Allen Hancock Foundation. L.A. Calif. Reprinted from Journal of Sedimentary
Petrology 23:8 pp. 226-234.

The Wilderness Society, Florida Keys Audubon Society, and Lewis Environmental Services, Inc.
1990. Is uncontrolled boating damaging thousands of acres of Florida's submerged seagrass
meadows? Marathon, FL. 33 p.

Woodburn K.D., B. Eldred, E. Clark, F. Hutton, and R.M.Ingle. 1957. The live bait shrimp
fishery of the west coast of Florida (Cedar Key to Nap)es).. Florida State Board of Conservation
Marine Laboratory, Technical Series No. 21: 33 pp.

Zieman, J. C. 1976. The ecological effects of physical damage from motor boats on turtle grass
beds in southern Florida. Aquat. Bot. 2: 127-139.

Zieman, J.C. and R. T. Zieman. 1989. The ecology of the seagrass meadows of the west coast
of Florida: A community profile. U.S. Fish and Wildlife Service Biol. Rep. 85(7.25). 155 pp.

Appendix A. Subcontractors report for the Florida Keys
region.

DRAFT FINAL REPORT

MAPPING ASSESSMENT OF VESSEL DAMAGE

TO SHALLOW SEAGRASSES IN THE FLORIDA KEYS, MONROE COUNTY

Submitted to: Florida Department of Natural Resources (DNR) - Frank

Sargent, Project Manager, and the University of South

Florida/Florida Institute of Oceanography, St. Petersburg,

Florida

F.I.O. Contract 47-10-123-L3
Submitted by: Curtis Kruer, Consulting Biologist, Summerland Key, Florida

Date: March 23, 1993

Introduction

This project involved aerial mapping and assessment Of vessel propeller

dredging and scarring damage to mainly shallow seagrass habitats in the

Florida Keys. The effort is part of an assessment by the Florida DNR Marine

Research Institute of boat propeller damage to seagrass meadows around the

coast of Florida. Rapid waterfront and recreational development in the Keys

during the 1970s and 80s, a dramatic increase in the number and power of

watercraft in the region, and the proliferation of liveaboards and jet-powered

thril1c.raft resulted in widespread impacts to shallow BeagraBs habitats

(mostly less than 5 feet low water depth), especially in areas of soft

substrates. The importance of healthy seagrasse,s in maintaining coastal water

quality, stabilizing bottom sediments, recycling nutrients, and providing

habitat for a variety of valuable finfish and shellfish is well documented.

Disturbance of large fish and wildlife (especially wading birds) that utilize

shallow seagrass flats by routine boating activity

appears widespread but is little studied.

The area surveyed in the Keys extends from North Key Largo (Dade-Monroe

County line) south and west to and including the Marquesas Keys, excluding

Everglades National Park (Figure 1). The Intracoastal Waterway forms the

boundary between waters of Everglades National Park and the Keys for purposes

of this assessment. The area of vessel damage was determined visually from the

air and mapped onto the largest scale map or chart available utilizing the

best fit polygon method of delineation. The degree of damage in each area was

estimated and categorized as light, moderate, or severe. For a subset of sites

additional information geared towards problem management was prepared.

Methods and Materials

Initial delineations were made onto navigational charts and topographic

maps in the airplane as impacted seagraBB areas were observed. Surveys were

conducted from a Cessna 152 or 172 and began west of Key West, later

proceeding east and up the Keys. Altitude was maintained at abo ut 6001 at

speeds of around 80 - 90 mph. In the Lower Keys, transects were flown on a

north-south orientation approximately 1,0001 apart traversing the shallow

water area between the Atlantic Ocean and the Gulf of Mexico. In the Middle

and Upper Keys, due to a narrower shallow zone, mapping was conducted as the

plane flew along the perimeter of shallow water flats and banks and over

shorelines. An effort was made to map midday during optimum conditions of

clear.skies, low winds, and clear water.

Two or more prop scare or grounding sites in close proximity (within

about 50') were deemed to represent a pattern and were enclosed in a polygon.

About I acre was considered a minimum size for a polygon based on the scale of

charts and maps used. Individual scars not enclosed in a polygon were drawn as

a line and an.chored on each end with an "x". The severity of impact within an

area was based on a visually estimated degree of impact from prop dredging and

displacement of sediment from 'the scars onto adjacent vegetated areas. A

"Comparison Chart for Visual Estimation of Percentage Composition" provided by

DNR was used to refine estimation of damage. Light impact (L) indicated that

less than 5% of the polygon was impacted, moderate impact (M) indicated 5-20%

of the area was impacted, and severe impact (S) meant more than 20% of the

area was impacted.

Collateral information used for mapping included 1991 color-infrared

vertical aerial film (91, x 9" images, 1:12,000) of the Keys provided by DNR,

35 mm oblique aerials shot in recent years, and personal knowledge of the
contractor. Ground-truthing by boat was used in a few locations to document

the accuracy of delineations made and measure the width of representative

scars.

In an effort to document why boatin g impacts were occurring a subset of

sites were assessed for the probable cause based on observed boating activity,

history of the area, and personal knowledge of the contractor. In addition,

management recommendations were considered that would reduce or eliminate

impacts at these sites.

Results and Discussion

As of the drafting of this final report a total of 18.9 hours of

airplane time had been committed to mapping, from October, 1992 to February,

1993. All but the area from Islamorada south to Seven-Mile Channel had been

mapped as of this draft, with the remaining area to be mapped as soon as

weather and water conditions allow. Draft delineations and levels of impact

recorded in the air were transferred onto clean cha rts and maps in the office

and provided to the Florida *Marine Research Institute. In addition to the

.area delineated and level of severity for each site, an identifying number in

sequence from west to east was provided for inclusion in the computer mapping

data base. Representative aerial photographs (35 mm slides) were taken of many

impacted areas.

Nautical charts and topographic maps onto which delineations were placed

were:

Marquesas Keys West topographic map (1:24,000, 1971)

Marquesas Keys East topographic map (1:24,000, 1971)

Cottrell Key topographic map (1:24,000, 1972)

Key West topographic map (1:24,000, 1971)

Chart 1144.1 (1:30,000, 1991) - Key West Harbor and Approaches
Chart 11445 (1:40,000, 1991) k 0

side A - Bahia Honda Key to Sugarloaf

side B - Sugarloaf to Key West

Chart 11448 (1:40,000, 1990) Big Spanish Channel to Johnston Key

Chart 11442 (part, 1:80,000, 1981) - Sombrero Key to Sand Key

Chart 11449 (1:40,000, 1990)

side A - Matecumbe to Grassy Key

side B - Grassy Key to Bahia Honda Key

Chart 11463 (1:40,000, 1987)

side A - Elliott Key to Tarpon Basin

side B - Tarpon Basin to Matecumbe

Flight records for mapping follow:

Date Area Hours Comments

10/08/92 west of Key West 2.0

10/18/92 west of Key West 2.0

11/19/92 Key West-Boca Chica 2.3

12/12/92 Boca Chica-Sugarloaf 1.8 turbid water

1.2/13/92 Sugarloaf-Big Pine 3.0

near Big Pine 3.8 with F. Sargent/DNR

02/11/93 N. Key Largo-Matecumbe 4.0 with F. Sargent/DNR

Approximately 700 individual impacted areas have been delineated to date

along with a number of individual scars. Impacted areas range in severity from

those with only a couple Of scars to severely impacted areas with numerous

scars and grounding sites and sizeable, previously vegetated areas filled by

displaced sediment. In addition, storm generated wavewash and surge was

documented, particularly in exposed locations, to erode old scarred areas

further impacting adjacent seagrasses by burial. As noted by Matthews et al.

(1991). virtually all seagras. s banks and flats in the Keys have some prop scars

with density generally greatest near developed islands and.in areas of high

boating activity. All user groups are responsible to some degree with large

commercial and recreational vessels (>25') responsible for the largest impacts

and groundings and smaller vessels (<25') and personal watercraft responsible

for numerous small scars and recently prop dredged channels in shoreline

areas. Water depth of seagraSBeS impacted ranged from the high intertidal zone

to about 5-6 feet deep at low tide. The deeper impacts were near commercial

ports at Key West and Stock Island, northeast of Big Pine where trap boats

shortcut through shallow channels, near Marathon and Islamorada where both

large commercial and recreational vessels dock, and in and along the

Intracoastal Waterway on the bayside of the Upper Keys.

Sediments in shallow seagrass beds subject to these impacts in the Keys

are extremely variable. Conditions range from very fine, silt size material

found on the edge of Florida Bay and in shallow embayments of the Lower Keys

to coarse, well sorted material in open water banks. Fine materials are easily

resuspended, emphasizing the value of bottom stabilization by healthy

seagrasses. But even banks with deep, coarse sediments, includ ing Porites

finger coral banks like those found around Rodriguez Key in the Upper Keys and

Pye Key and Key Lois in the Lower Keys, are heavily impacted with poor chance

of recovery. Wave and current scour now prevents or retards the accumulation

of fine sediments in these scars. Many prop dredged channels (i.e. north Niles

Channel) now funnel currents altering sheet flow (and possibly animal

movement) across flats and scouring bottom sediments, often to bedrock.

Turbulence and sediment resuspension from regular, often near continuous, use

of some prop dredged channels prevents revegetation and increases turbidity in

the surrounding area. Sediment characteristics, usage, location, and energy

regime appear to be factors that determine the speed of natural revegetation.

Kenworthy et al. (1988) concluded that boat wake waves substantially elevate

the bottom shear stress along shallow seagrass beds with possible implication

for Beagrass health. This wearing away of shallow Beagrasses can be noticed'

along the edges of the open water oceanside access channels for the large

sportfishing fleet in the Upper Keys, such as at Whale Harbor and Teatable

Relief Channels. In addition, surge and sediment resuspension on the bottom

often occurs to a depth of 7 to.8 feet or more when commercial vessels hauling

heavy traps ply local waters.

Most of the impacted areas mapped were defined as light impact but many,

especially near developed islands, were assessed as moderately to severely

impacted. Acreage figures of these areas are to be generated by the DNR once

mapping is completed. Table 1 lists by site number the moderately impacted

areas from a subset of sites (Lower Keys, Marquesas Keys to about Snipe Key,

sites 1-255) for which additional information was collected. Table 2 lists the

severely impacted sites from this same subset. This information is provided as

an possible approach to closely examine the site specific basis of shallow

water impacts for the purpose of management of the problem. Considered also

for each Bite could be the history of traffic in the area and the type of

craft responsible. Assessment of the probable causes of different impacts

revealed the following (often more than one cause) reasons:

1. Vessels attempt to take shortcuts even,though water of an adequate

depth is available nearby or vessels simply pass through water too shallow for

the draft of the vessel. These actions may be either accidental or purposeful.

with the average size, draft, and power of vessels increasing in the KeYB,
locations where oversized vessels routinely plow through waters too shallow*

are becoming more widespread. The recent proliferation of "flats" boats, in the

Keys and competitive promotions by manufacturers of their vessels ability to

run through very shallow or "skinny" water has resulted in an increasing in

detrimental boating on shallow flats.

2. Vessels travel through marked channels with an inadequate number of

.markers or where the markers are poorly located, i.e. not as shown on charts

or in or immediately adjacent to shallow water. If a boater passes on the

wrong Bide of a marker located on the edge of a flat as opposed to further in

the deep part of the channel, the boater may run aground. Most KeYB boaters

are not familiar with the Coast Guard required day marker symbols and

numbering system and hence a single marker presents a problem if the boater is

unable to read the water. Many heavily impacted areas are in or near marked

channels.

3. Illegal aids to navigation (i.e. PVC markers, reinforcing steel

lengths, marker buoys) are widespread in Keys waters and proliferating

rapidly. Only the individuals placing these markers know what is intended

resulting in many boaters passing unexpectedly through shallows, often in an

unsafe fashion. Many illegal aids are placed in very restricted passageways
and some are still being placed to allow or encourage channel creation.

4. There is extensive shoreline development in the Keys adjacent to

shallow seagrass flats. Much prop scarring is a result of boaters attempting
to access shoreline residences that may or may not have a dock or from boat@rs

recreating in shallows near residences. Although current rules limit- new docks

to waters greater than 4 feet in depth at low tide, there are many existing

docks located in shallow water with poorly defined, if any, access channels.

Many old channels in open water areas are subject to filling and are now

maintained by prop dredging. Although docks cannot now be permitted in shallow

water, illegal docks are often built leading to seagraBS impacts. Many dredged

canals leading from old Bubdivisions terminate in relatively shallow water

causing access problems as population density and vessel Bize increases. High

powered Bpeed boats from residential areas race across very soft shallow flats

with little regard for depth.

5. Hundreds of commercial marinas, boat and personal watercraft rentals,

and public boat ramps are in close proximity to shallow seagraBses where few

channel markers exist. The result is that boats are concentrated in and near

shallow areas, with usage by large fish and wildlife probably decreased. The

U.S. Fish and Wildlife Service (1992) determined that boating activity was

adversely affecting wildlife resources (especially birds) in Keys wildlife

refuges. It seems likely that most large, shallow water animals (i.e. tarpon,

bonefish, permit, sharks, barracuda, snappers, stingray, eagle ray, COWfiBh,

sawfish, bottlenose dolphin, small Bea turtles, and manatee) view fast boats

as predators, with the expected reaction. Although most information is

anecdotal, many commercial and recreational fishermen believe that boating

activity affects the,habits and abundance of fish in heavily traveled areas.

Some of the worse prop dredged areas are.near marinas catering to fishermen,

where ample justification exists for providing safe, low impact boating.

6. Numbers of liveaboard vessels, both residential and commercial, have

increased rapidly in recent years. Documented were problems of anchor and

chain damage as vessels continually swing on anchor, keel andoutdrive damage

when vessels anchor in waters too shallow, and severe prop dredging by

commercial liveaboards (principally spongers) when passing from one shallow

bay or channel to another.

A review of Keys aerial photographs from the 1950s revealed that prop

dredging has occurred here for a considerable period of time. But with an

increasing and more affluent residential population, the increasing popularity

,of boating, fishing, and diving, and a vastly increased tourist population the

problem has become much more widespread. Based on extensive experience of the

contractor with the problem in the Keys it is obvious that just in the last

.few years impacts have spread and become a much more serious cumulative

problem. New prop dredged channels continue to appear, some thousands of feet

long, and now provide larger boat access into areas not previously heavily

travelled. Many shallow flats and banks are now heavily eroded due to numerous

scars and grounding events.(i.e. large bank north of the east end of the

Seven-Mile Bridge and banks north of Long Key Bridge).

Management Recommendations

The first step of identifying and managing this resource problem is now

being taken by the Florida DNR and very timely considering the level of impact

to these important public resources. Surprisingly, few if any new channel

markers have been placed in Keys waters in recent years even though public

sentiment has been strong in recent years that this effort is an. important

component of safe, low impact boating. New programs are currently underway in

both John Pennekamp Coral Reef State Park and Lignum Vitae Key State Botanical

Site to prohibit motorized access onto shallow flats and treat prop dredging

as damage to protected resources. Monitoring of the effectiveness of these and

other management strategies, both from the air and on the water, is critical

to their success. The Monroe County Department of Marine Resources is about to

release a draft Boating Impact Management Plan that may be incorporated into

the draft management plan for the Florida Keys National Marine Sanctuary.

Ample opportunity and justification now exists to manage boating impacts in

the Keys. Based on observations incorporated here a multi-faceted approach is

necessary to deal with the wide range of user groups, activities, and physical
impacts. Recommended is a 4-point approach that can form the basis for

management to eliminate or significantly reduce theimpacts at the moderately

and severely impacted sites identified here and prevent an increase at those

site only lightly impacted now.

1. Education

The Keys are one of the most popular diving and fishing destinations in

the world with millions of visitors each year. The value of education about

resource impacts is obvious but in an area where there is a continual influx

of new visitors, and seasonal and permanent residents, there must be other

mechanisms to insure compliance and accomplishment of resource management

goals. Graphic aerial photography of vessel damage to seagrasses has proven

useful in the past to educate managers, decision makers, and the public about

the issue. Acknowledging the.need to limit increases in vessel size, draft,

and power in shallow areas, and reduce these in some areas should be an

important educational goal.

2. Channel Markina

It is imperative that deviation be allowed from the Coast Guard

requirements Of Bignage and symbols that might preclude or discourage simple,
easily installed and maintained markers with directional arrows. Conventional

day markers are very useful in deep, open water channels and programs should

proceed to relocate markers to the center of channels providing buffers along

the edges of adjacent seagrass flats. Day markers should be gated in most

locations and extend well beyond the entrances to channels. In impacted,areas

where public funds are expended to protect seagrasses, mechanisms must be

developed to require the use of channels. In sensitive areas marking should be

designed to solve problems, not create new ones by improving or facilitating

boater access. Illegal aids to navigation should be removed as criteria are

established and new markers put in place. The resource benefits of an

expensive marker system are negated if illegal markers continue to be

widespread with ever increasing prop scarring around them. Benefits are also

negated if extensive prop dredging and turbidity are allowed within marked

channels.

3. Enforcement

Prop dredging and physical damage to seagrasses by vessels must be

regarded as physical destruction of protected public resources. Considerable

prop dredging in the Keys is Willful, particularly where repetitive activities

occur, and much of the rest is due to simple negligence. Interpretive

education, warnings, and citations are requirements of a successful

enforcement.program. Voluntary compliance has not p.roven adequate in the past

in the'Florida Keys to solve resource problems.

4. Restricted Boating Areas

Programs currently being put in place by the Florida DNR (Pennekamp Park

and Lignum Vitate Botanical Site) and the U.S. Fish and Wildlife Service

(Lower Keys refuges) are good examples of moderate restrictions to protect

sensitive resources from physical impacts while allowing compatible public

access. Other shallow areas are being considered for management by the Florida

Keys National Marine Sanctuary. other very shallow channels, flats...and

embayments in the Keys where there are little, if any, boating activityand

seagrass impacts should be considered for access restrictions such as idle

speed or no motor zones before problems develop. Monitoring of the success or

failure of these efforts is critical to future management of other seagrass-

areas where physical impacts and unacceptable levels of disturbance of shallow

water fish and wildlife are occurring.

References

Kenworthy, W. J., M. S. Fonseca, and G.W. Thayer. 1988. A comparison of wind-
wave and boat wake-wave energy in Hobe Sound: implications for seagrass
growth. Ann. Rep@ to U.S. Fish and Wildlife Service Sirenia Project,
Gainesville, FL , 21 pp.
Matthews. T.R., A.C. Lazar, and J.H. Hunt. 1991. Aerial observations of
boating impacts to shallow water grass beds in the Florida Keys. Report to the
Florda DNR Off. Mar. Progs. and Plan. 12 pp.

U.S. Fish and Wildlife Service. 1992. Management Agreement and Environmental
Assessement for submerged lands within
boundaries of the Key West and Great White Heron National Wildlife Refuges.
U.S.F.W.S. Regional office, Atlanta, Ga. 76 pp. plus appends.

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Table 1. Prop dredging survey summary information for moderately impacted
sites mapped from the Marquesas Keys to Snipe Key in late 1992 and early
1993 (draft).

Adjacent Probable 2
Site # Severity island cause Recomms. Comments

------ -------- ----------------- -------- -------- -------------------------------
13 M Marquesas Keys S,A E Shallow channel-between
islands with popular beaches
15 M Marquesas Keys S,A E Shallow channel between 2
islands
32 M Marquesas Keys S,I E Entrance to natural channel
46 M Boca Grande Key S,CH CH At entrance to main channel,
existing markers (#s 17 and
18) reflected on chart 11441
too far apart, marker 18 in
shallow zone, vessels pass on
shallow side.
50 M Boca Grande Key S,CH CH Markers #s 13 and 14 not
located as shown on chart
11441
75 M Archer Key S,CH EN,CH Adjacent to single marker # 8
shown on chart 11441, oversize
vessels; need gated markers.
105 M Mule Key S,CH CH,EN Confined area between channel
markers, used by oversized
vessels
113 M Mule.Key S,CH E Area of concentrated traffic
near channel markers
121 M Key West S E Isolated bank (Middle Grounds)
in center of Northwest Channel
123 M Wisteria Island S,CH,L E,EN,CH Heavily traveled anchorage on
west edge of Key West Channel
127 M Fleming Key S,CH E,CH Inadequately marked channel
through large bank
142 M Fleming Key S E,EN on inside of several markers
145 M Fleming Key S E,CH On edge of main channel near
marker
150 M Key West S,P E,EN,CH Outside of markers in access
to-Garrison Bight
151 M Key West S,CH,P E,CH Inside Garrison Bight, outside
of partly marked dredged
channel
152 M Key West S,CH,P E,CH Inside Garrison Bight, outside
of partly marked dredged
channel
155 M Sigsbee Park S E,CH At end of dredged area
156 M Key West S,A E,CH Boats accessing dredged
channel
157 M Key West S,CH,P E,EN,CH Cow Key Channel, part marked,
part not marked, high speed

1. S=shortcut, CH=markers, I=illegal aids, A=access, P=proximity, L=Iiveabor.
2. E=education, CH=new or improved markers, EN=enforcement, R=restricted area

Table 1. Prop dredging survey summary information for moderately impacted
sites mapped from the Marquesas Keys to Snipe Key in late 1992 and early
1993 (draft).
Adjacent Probable' 2
Site # Severity island cause Recomms. Comments

------ -------- ----------------- -------- -------- -------------------------------
traffic
163 M Stock Island S,p E,EN,CH Adjacent to Safe Harbor
Channel
165 M Stock Island S,P,L E,EN,CH Anchorage east of Stock island
in Boca Chica Channel
166 M Stock Island P,L E,EN Anchorage east of Stock Island
in Boca Chica Channel and near
ramp
174 M Boca Chica S E,EN At entrance to dredged part of
Boca Chica Channel
181 M Bay Keys S,I E,EN Commercial tour boats and
recreational boats accessing
Bay Keys from the south
201 M Lower Harbor Keys S,I E,EN Long, illegally marked channel
204 M Channel Key S,I E Part of old Backcountry
Waterway
207 M Channel Key S,I E,CH Cut through bank between
islands
223 M Fish Hawk Key S,I E,CH Cut through long linear bank
232 M Geiger Key S,I,A E,EN Shallow channel leaving
residential canal
236 M Saddlebunch Key S,CH E,CH On bank near marked channel
238 M Big Coppitt Key CH,A E,EN Marked access to canal trailer
park
245 M Halfmoon Key S,A,I E,EN Access to shallow embayment
251 M Mud Keys S E,CH Channel leaving Waltz Key
Basin

1. S=shortcut, CH=markers, I=illegal aids, A=access, P=proximity, L=liveabor.
2. E=education, CH=new or improved markers, EN=enforcement, R=restricted area

Table 2. Prop dredging survey summary information for severely impacted
sites mapped from the Marquesas Keys to Snipe Key in late 1992 and early
1993 (draft).
Adjacent Probable 2
Site # Severity island cause Recomms. Comments

------ -------- --------------- - ------ --------- --------------------------------
7 S Marquesas Keys S E,EN From large vessel in early
1980s, now enlarged
129 S Wisteria Island S,CH,L E,EN,CH heavily traveled anchorage on
east side of Key West Channel
138 S Fleming Key s,i E,CH At shallow end of a natural
channel
158 S Stock Island A E,EN Boats accessing residential area
in shallow water
160 S Key West A,L E,EN Cow Key Channel liveaboard
anchorage and Cow Key Channel
south of bridge
170 S Stock Island S E,EN,CH Large vessels shortcutting into
Boca Chica Channel
231 S Geiger Key S,I,A,P E,CH,EN Access to Geiger Key Marina and
area

1. S=shortcut, CH=markers, I=illegal aids, A=access, P=proximity, L=liveabor.
2. E=education, CH=new or improved markers, EN=enforcement, R=restricted area

Appendix B. Copy of a newspaper article discussing the
problem of propeller scars in shallow seagrass.
beds. Kevin Lollar, Fort Myers New-Press,
January.2, 1993.

Boaters
'cutting
their own
throats'
Props rip sea grasses

By KEVIN LOLLAR
News-Press staff writer

From the boat on the
clear water off
Pineland, it doesn't look
like much to worry
about.
Just a long white, sandy strip
where the turtle grass doesn't grow
- a prop scar from a power boat
"Boaters who go out and cut up
sea-grass beds are really cutting
their own throats," said Robert
Repenning, manager of the
Southwest Florida Aquatic
Preserves. "Most of those boaters
are out here to fish, and without sea
grasses, you won't have nearly as
many fish."
It's the old food-chain thing. Sea

See GRASS/
back page this section

GRASS:
Provide
food and
shelter
From Page 1A

grasses provide habitat for many
small creatures, which are eaten by
larger creatures, which are, in turn,
eaten by even larger creatures, such
as snook, sea trout and redfish.

One square meter of sea grass
for example, can contain 3,000
polychates (small marine worms)
and 1,500 amphipods (small
crustaceans), important food
sources on the lower end of the
chain.

Besides that, two dozen species of
shrimp, 148 species of algae, many
species of crab (including blue and
stone crabs), snails and other
mollusks, sponges, and plenty more,
live in sea-grass beds.

"We're talking a lot of
productivity here," Repenning said.
"If you follow it up the food chain, it
eventually becomes valuable to us.

"For fish, sea-grass beds are a
supermarket and a home. They
provide food and shelter-little fish
can hide to keep from being eaten by
big fish. Sea-grass beds provide all
the stuff fish need to get going."

Now, think about this: 70 percent
of Florida's commercially valuable
fish spend all or part of their lives in
sea grasses.

Sea grasses also help keep water
clear by trapping fine sediments and
particles; they stabilize the bottom
with their roots, much as land
grasses prevent soil erosion; and
floating sea-grass leaves carry
nutrients to other areas.

Obviously, sea grasses are a vital
part of Florida's ecosystem, but on
both coasts, sea-grass beds are being
cut to pieces by boaters. The Keys
have the most seriously scarred
grass beds-estimates go as high as
10,000 acres of prop damage.

Any heavily traveled shallow
waterway, though, including the
beds off Pineland, will be
crisscrossed with scars.

Prop scarring is not just clipping
the tops of sea grass with a propeller.
It's plowing through the sediment,
hacking up roots and all.

And when you talk prop scarring,
you're talking almost exclusively
about recreational boaters.

"A lot of people blame
commercial fisherman because they
see the commercial guystaking their
boats into places recreational boats
can't go." Repenning said, "But
commercial boats can run in six

Florida Marine Institute
PATHS OF DESTRUCTION: Propelller scars slice like claw marks across sea-grass beds near Pine Island in this photograph taken from
a Florida Marine Patrol plane. Most prop damage in grass beds is done by recreational boaters.

"We're talking a lot
of productivity here.
If you follow it up the
food chain, it eventually
becomes valuable to
us."
ROBERT REPENNING
Southwest Florida
Aquatic Preserves
________________________

inches of water and not scar the
bottom. The commercial fisherman
know where they can go without
getting into trouble."

A small prop scar can take up to
five years to heal; large scars can
take 10 years.

In many cases, prop scarring
arises from boater ignorance.

"A lot of people move down here
from the Midwest, where they're
used to boating on the Great Lakes in
hundreds of feet of water with deep-
draft boats." Repenning said. "They

put those boats in Charlotte Harbor
and start running aground every turn
they take.

"Unfortunately, to run a boat in
Florida, all you need is money to buy
or rent a boat. There's no skill
required."

Many boaters don't know how to
read the water. Many don't know,
until too late, that water levels can
change from a safe six feet to an
unsafe six inches in an instant. Some
areas aren't well marked, and even
in marked areas, some people don't
understand the markers.

Then, again, some people just
don't care, said Jud Kenworthy, a
research biologist for the National
Marine Fisheries Service.

"There's just kind of an
unlimited-access attitude that goes
with being on the water," he said.
"It's a big open space; you're free to
go where you want to go out there.
These people lack an understanding
of the value of the resource."

Certainly, some boaters will say,
"Hey, so what if I run my boat
through a sea-grass bed? What
harm's a little scar going to do?"

Lots, said Frank Sargent, a

remote sensing analyst at the Marine
Research Institute in St. Petersburg.

"It's really a major problem in
Florida," he said. "Granted, your're
going to have some areas that get
scars and won't really be harmed.
but it's the repeated scarring that
does the damage. It takes a lot of time
for sea grasses to get re-established,
and some never do."

Sea grasses are constantly
threatened by human activities-
dredging and filling, oil spills,
temperature changes from power

plant discharge, various kinds of
pollution.

Although the individual resident
really can't do much about these
threats, he or she can help sea
grasses by simply not chopping up
the grass beds with his boat.

"If you can't convince people
with arguments about resource
management, ask them how much
the paid for their boat," Repenning
said. "Sucking up a bunch of mud can
just burn a motor up. And running
aground can sure bang up your hull."

TIPS
________________________________________________________________________

Read the water. Grass grass is shown as light
beds look like dark areas green or "Grs."
in the water. Polarized Stay in deep water. If near
sunglasses help you see shallow water, drive
grass beds. cautiously and slowly.
Pay attention to channel If you do run aground,
markers. stop engine and tilt the
Use navigation charts: Sea motor up; pole or walk the
boat back to deep water.

Appendix C. Site specific actions to manage and protect
shallow water seagrass habitats in the Windley
Key area. Proposed by Curtis R. Kruer, the
subcontractor for the Florida Keys portion of
this project.

DRAFT PROPOSAL TO MANGE AND PROTECT SHALLOW WATER SEAGRASS HABITATS
IN THE WHALE HARBOR CHANNEL/WINDLEY KEY AREA

Background

The area proposed to be managed is in the upper Florida Keys
(fig.1) and encompasses a variety of shallow marine habitat types
as a result.of the change form exposed ocean conditions to more
protected waters of Florida Bay (Fig. 2). It also includes the
most heavily prop scarred shallow seagrass area in the Florida Keys
(Hunt et. al. 1991, pers. observs.). Recent comparison of aerial
photographs of the area in the md 1980s to current conditions
revealed substantial increases in prop dredging and the loss of
seagrass cover on shallow flats and the edges of channels.
Additional channels have been cut through very shallow water and
mangroves by personal watercraft and small outboards. Intense
boating and personal watercraft activity results form 4 commercial
marinas, including the large sportf ishing vessel fleet at the
Holiday Isle and Whale Harbor marinas, located on either side of
Whale Harbor Channel. Unregulated thrillcraft use from rentals at
these and other marina occur virtually nonstop during daylight
hours. Racing power boats are a common sight and powerboat races
are routinely run in the area. Numerous illegal aids to navigation
have been placed with some markers and signage evidently recently
pla@ed as a result of requirements on submerged lands leases.

The seriousness of physical impacts, the extent of sovereign lands,
and the diversity of boating activity here all combine to create a
management opportunity that, if successful, can be used as a
prototype for management of other impacted areas. The fact that
the area is outside of an otherwise protected park or preserve
lends significance to a local, state, and federal effort to design
and implement management.

Proposal to Manage Boating Impacts

1. The area (see attached NOAA chart) extending from beyond the
seaward edge of the Atlantic Ocean seagrass flats north to the
boundary of Everglades National Park should be managed as a unit.
This area is about 5 square miles, including land area . A
computer mapping data base would be necessary to define natural
habitats, water depths, channels, and land based and marina
facilities. Only one facility exists on the Florida Bay side of
U.S. 1 here, the rest are on the Atlantic Ocean side. With
available aerial photography (early 1971, 1983, and 1992), a
historical perspective could be put on prop dredging and wave
energy scour of seagrasses.

2. Management needs to be designed and implemented a sa collective
"special area" effort by local, state, and federal agencies with
responsibilities to protect and manage submerged natural resources.
Specific goals need to be established at the onset, such as a
reduction by 90% of new prop scars over a given time frame,
eliminated boating accidents, and management without precluding

traditional uses of these waterways (transit, fishing, swimming).
Monitoring of the effectiveness of the plan after implementation is
critical to its success and its value as a precedent.

3. Requirements of state submerged lands leases need to be
incorporated into this management plan and possibly modified to
meet the needs of resource protection. Existing legal authority to
protect public resources in these waters need to be clearly
established an shortfalls identified.

4. The following four point plan needs to be incorporated into the
overall management of the area. Seagrass protection programs being
implemented at the John Pennekamp Coral Reef State park and
Lignumvitae Key State Botanical Site, as well as elsewhere in
Florida, should be reviewed.

a. Edu cation

The management plan and its requirements need to be widely
publicized in the vicinity with land based signage and literature
provided at marinas and rental facilities. Conditions of state
lands leases to the marinas could include a responsibility to
insure future production and distribution of materials. Promoted
has to be a recognition of the severe and worsening impacts
currently resulting from manfs activities. Promoted also must be
the concept of the need for a radical change in the way shallow
waters of the Keys are used. Individually, the activities may be
relatively harmless, but the cumulative impact of numerous, often
constant activities, and the productive habitats in which they
occur are the root of the problem.

b. Channel Marking

critical to the success of any plan is the marking of passageways
for vessels to transit from marina facilities and docks to open
waters of the Atlantic or'Florida Bay. Virtually every access
point through.shallow waters (< - 41 MLW) could be managed with
markers. A minimum number of markers should be placed but this
depends.on implementation of other points in the plan. A review of
aerial photographs and navigational charts for the area show that
the marking of 2-3 transit channels on each side of U.S.,1 could
provide access to open waters (Fig. 2). Mark access, where
adequate depths exist, f rom marina and other dock facilities along
shorelines would be necessary to lead to the transit channels. It
appears that additional conventional large day markers would be
appropriate in the main oceanside channel while stout PVC with
distinctive arrows would best for the other channels. Only the
main channel into the ocean and the entrance to the marina basin at
Holiday Isle currently has Coast Guard approved day markers.

c. Enforcement

Necessary to insure compliance with the plan and critical to
meeting established resource protection and improved safety goals.

Increased attention t6 the area initially may be necessary.
Simplified management would make for efficient and effective
enforcement.

d. Restricted Boating. Zones

Consistent with resource protection plans for similar stateowned
bottoms in waters of the Pennekamp and Lignumvitae areas is the
concept of no combustion engine zones in water shallower than 3
f eet deep at low tide (tops and edges of banks) and idle speed
zones near shorelines and offshore from bank edges. In combination
with marking, these management tools provide the means to stop prop
scarring in specific areas and provide safe access to an from
marked channels (Hunt et. al., 1991). The Florida Keys National
Marine Sanctuary Advisory Council has recently approved a
resolution recommending setting idle speed zones within 600f of
shorelines and the edges of seagrass flats in the Keys. Recent use
of shallow areas as commercial watersports zones would be
eliminated as incompatible with resource protection. Consideration
should be given to making the main offshore channel to the ocean
(about one mile long) an idle-speed zone to enhance safety and
protect the bank edges from continued erosion and destabilization
by large vessel wakes.

Appendix D. Agencies which have expressed an interest in actively participating in the
Department of Natural Resources seagrass propeller scar damage management and education
project.

Lee County - Department of Natural Resources
Chuck Litowski

Collier County - Department of Natural Resources
Mack Hatcher or Maura Kraus

Sarasota County - Department of Natural Resources
John McCarthy, Ed Freeman, Belinda Perry and George Tatge.

Monroe County Division of Marine Resources
George Garret and Doug Gregory

Pinellas County - Department of Environmental Management
Will Davis and Eric Fehrman

Florida Inland Navigation District.
David Roach and Brent Waddel

Jupiter Inlet District
Mike Rella

Brevard County Office of Natural Resource Management
Conrad White

Indian River County
Roland Deblois, Environmental Planner

Martin County
Mark Tamblyn, Environmental Planner

NOAA COASTAL SMICES CTR LIBRARY
ll ......
-'-j @[email protected] 1