Atlantic and Gulf Rapid Reef Assessment

Initial Flagrra Field Report on

Coral and Algal Communities

The reefs of the Florida Reef Tract are the only living tropical coral reef system in the continental United States. However, several interacting factors have contributed to the consideration of this ecologically, economically, and aesthetically unique system as an “ecosystem at risk”. The geographical location of Florida reefs near the northernmost limit of reef development and adjacent to a large and rapidly growing urban center makes this system specially vulnerable to coral disturbances like eutrophication, sedimentation, and pollution commonly associated with coastal development.

Southeast Florida has considerable industrial and agricultural activities that are important sources of pollution in nearshore waters. The Florida Reef Tract and the two adjoining coastal lagoons, Biscayne Bay and Florida Bay (Fig. 2), are sites of extensive recreational and commercial harvesting of fish and shellfish. These activities provide a multi-million dollar annual income to the local economy, but have resulted in significant overfishing and depletion of harvested fish stocks. During the summer of 2003, a team of scientists from the University of Miami surveyed reef communities of the Florida reef tract using the AGRRA Protocol to evaluate the current status of Florida’s reefs by documenting the condition of coral, fish, and macroalgal communities. Here only are the initial results of assessment of the coral and Algal communities.

Figure 1. The selected sites for FLAGRRA in four different regions

Figure 3. Mean colony size (±1 S.E.M) of colonies of Montastraea cavernosa, M. faveolata, Siderastrea siderea, and Porites astreoides by habitat type.

Results

· Coral Community Composition--A total of 3049 stony corals were measured at the 45 sites surveyed during FLAGRRA. The three most abundant coral species were Porites astreoides and Siderastrea siderea, which represented 18 and 17% of all colonies encountered respectively. Colonies of the genus Montastraea, one the main reef-building taxon in the region are 21.5 % of all colonies.

· Coral Cover-- Percent coral cover showed defined habitat as well as region-specific patterns. When data were grouped by habitat, mean coral cover was significantly higher on lagoon patch reef habitats (30%) compared to spur and groove (18%) and hardbottom habitats (7%) (ANOVA, p < 0.01). However, mean coral cover on spur and groove habitats was significantly higher on the Lower Keys compared to similar habitats of the Upper Keys (t test, p < 0.01).

· Colony Size-- For the most abundant coral species (see above), mean colony size was significantly smaller on hardbottom habitats of the Florida Keys (see figure 3) compared to patch reefs and spur and groove habitats (ANOVA, p <0.01). While the mean size of Montastraea colonies was higher in the Middle and Lower Keys (Fig 1.), the opposite patterns were documented for Siderastrea siderea and Porites astreoides, which have larger colony diameter in the northern regions of the Florida Reef Tract.

· Partial Mortality--When all colonies were grouped together, the mean of old partial mortality for the Florida Keys was 18.4% while recent partial mortality was only 0.6 %. Levels of old partial mortality in the ten most abundant stony coral species ranged from 9-48 %. Acropora spp. and Montastraea spp. had the highest average percent old mortality (18.4%) in the entire Florida Keys Reef Tract, while Porites astreoides had the lowest (0.6%).

· Coral Diseases--The incidence of coral diseases was low in the Florida Keys as only 29 corals colonies were infected (0.95 % of colonies). The diseases or syndromes identified during our surveys included dark spot syndrome (mainly on S. siderea), white band disease (on Acropora), black band disease, and yellow blotch disease (on Montastraea spp.).

· Juvenile Corals--Fifteen juvenile coral species or genera were observed during FLAGRRA (Table 1). The three most abundant juvenile corals were S. siderea (31.6 % of colonies), P. astreoides (19.5 %) and S. radians (14 %).

· Macroalgal Community Composition and Urchin Abundance-- CCA (crustose corallines) was the predominant functional group on reefs of the Upper and Lower Keys due mainly to the presence of spur and groove habitats in these two regions. The abundance of D. antillarum was extremely low; only 4 urchins were recorded from a total of 269 10-m² transects. The low abundance prevented any analyses of urchin distribution data based on habitat or region.

· Acroporid Populations-- Isolated colonies or patches with scattered colonies of A. palmata were also observed at French Reef, North-North Dry Rocks, Elbow Reef, Sombrero Reef, Looe Key Reef, and Western Sambo Reef. A total of 189 A. palmata colonies were measured in these surveys. Mean coral cover on these sites was 17.1 % (S.E.M = ± 8.8) and ranged from 1-32 %. Mean colony size of Acropora palmata was similar in the Upper Keys and the Lower Keys (t test, p > 0.1).

Participants: Diego Lirman (Field Coordinator), Robert Ginsburg, Marilyn Brandt, Wade Cooper, Amit Hazra, Jonathan Kool, and Aletta Yniguez.

Return to AGRRA home page	.	Last updated: 24 June 2004
Robert N. Ginsburg Atlantic and Gulf Rapid Reef Assessment MGG-RSMAS, University of Miami 4600 Rickenbacker Causeway Miami, FL 33149 USA	.	Tel: (305) 421-4664 Fax: (305) 421-4094 Email: agrra@rsmas.miami.edu URL: http://www.agrra.org/

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