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water column, thereby helping to build seagrass beds. Halodule
wrightii and the two species of Halophlla arc much smaller and
generally are considered to be fringing or pioneer species that
inhabit tho margins of major seagrass beds and tolerate environmental
conditions not suitable for the larger species.
The unique aspect of seagrass communities in the Florida Big
Bend area is the extended nature of the deeper, fringing zone
dominated by H. decipieno, H. engelnannl, and various macroalgal
species. Ground-truth data indicate that macroalgae account for an
average of 21% of total blade density seen here. Ground-truth data
also indicate that approximately 44% of the area mapped as sparse
seagrass beds on the basis of aerial photographs, was live-bottom
habitat that could not be differentiated from seagrass beds in the
aerial Imagery.
In addition to the spatial zonation patterns of seagrasses noted
in this study, seasonal variability in seagrass bed density and
species composition was evident, especially in the sparse offshore
beds. At moot offshore Signature Control Stations sampled during
Cruise 2 (February), blade densities were 50% to 90% lower than those
noted during Cruise 1 (October to November), and H_. declplena had
disappeared. Halophlla engelmannl persisted, but many Instances of
wave stress and uprooting were evident during Cruise 2. Temperature,
light, and wave action are likely to be important variables
influencing both spatial and seasonal abundance patterns in these
deep seagrass beds.
The ecology of deepwater seagrass/algal beds In the Florida Big
Bend area has not been studied, but these habitats could play
Important roles In this productive environment. Future studios
should focus on primary productivity, influential environmental
variableo, and associated flora and fauna of Big Bend area seagrass
beds.
Literature Cited
Chelsea International Corporation. 1983. National Marine Sanctuary
Site Evaluations Recommendations and Final Reports. A report
for the National Oceanic and Atmospheric Administrative, Office
of Ocean and Coastal Resource Management Sanctuary Program
Division. Contract No. NA82-SAC-00647.
Continental Shelf Associates, Inc. 1983. Annotated bibliography of
publiohod research dealing with light/seagrass relationships. A
report for tha Florida Department of Environmental Regulation,
Tallahassee, FL. 13 pp.
Continental Shelf Associates, Inc. 1984. Seagrass beds and
surficial sodlmant types found in Clearwater Harbor-St. Joseph
8ound, Florida. A report for the U.S. Army Corps of Engineers,
Mobile District, Mobile, AL.
Dawes, C. J., K. Bird, M. Durako, R. Gooddard, w. Hoffman, and R.
Mcintosh. 1979. Chemical fluctuations due to seasonal cropping
effects on an algal seagrass community. Aquat. Bot.
6(1):79-86.
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