The ecology and distribution of reef-building corals on four south Florida reefs

Burns, Thomas

This study examined the structure and diversity of the scleractinian corals on four reefs in Biscayne National Park: Pacific, Ajax, Long, and Triumph Reef. The shallow fore-reefs exhibited lower species diversity and coral cover than did deeper areas. It is hypothesized that cold temperatures and tropical storms are the most important environmental factors affecting these reefs. Graphs and tables present the data. Line-intercept transects in three depth-zones between the surface and 18 m on four consecutive shelf-edge reefs in South Florida (25° 29' to 25° 22' N) were used to study the structure and diversity of the hermatypic coral (Scleractinia) community. Low diversities, low coral cover and colony abundance, and the small size of colonies indicated that this area is not an optimum habitat for reef-corals. Temperature sensitive acroporids and other shallow fore-reef species were scarce and small. Species diversity, evenness, and Shannon-Wiener diversity in most cases increased with depth. Montastrea annularis and other corals reached greater abundance and size in the deep fore-reefs. The results suggest that cold surface water in winter is the major control of the distribution of hermatypic corals with depth on these reefs. The shallowest zone is stressed more frequently and severely by water temperatures below the tolerance levels of all but the hardiest corals. Differences in the abundance of several species and diversity among the four neighboring reefs indicate that exposure to environmental stress varies within the 13 km from Triumph to Pacific Reef. Hydrodynamic conditions varying with the location of reefs may determine magnitudes of stress or frequencies of disturbance from cold or sediment-laden bay water flowing out of tidal passes.

The ecology and distribution of reef-building corals on four south Florida reefs

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