Hard Substrata Community Patterns, 1-120 M, North Jamaica

Tropical marine communities from shallow-water (<30 m) carbonate environments are often dominated by hermatypic scleractinian corals with lesser amounts of crustose coralline algae and endolithic demosponges. Living cover is typically high (80-100%7p). Along the north-central coast of Jamaica and at many western Atlantic sites, communities existing below 55 m inhabit a vertical to overhanging wall of reef limestone, the deep fore reef, which extends to approximately 130 m. At 60 m the community resembles that of shallower water, although scleractinians are less abundant and encrusting and erect demosponges are much more abundant. Coralline algae and macroalgae are also important space occupants at 60 m and living cover approaches 65%. Encrusting sponges and coralline, filamentous, and macroalgae predominate in the middle region of the deep fore reef. A low-diversity assemblage occupying 40% of the substratum and dominated by diminutive encrusting and endolithic? demosponges and largely endolithic filamentous algae occurs from 100-130 m, the lower limit of the deep fore reef. Community structure and zonation on the shallower reefs is controlled by a number of biotic and abiotic factors, most notably predationlgrazing, light intensity, and turbulence. On the deep fore reef, grazing and turbulence are greatly reduced. While reduced in intensity, light continues to exert a strong influence on community bathymetric zonation. Sedimentation also exerts an important control on the spatial distributionf the deep fore-reef biota with the most diverse assemblages flourishing in areas protectedfrom sediment. Despite aregime of reducedisturbance in deep water, community diversity remains relatively constant to a depth of 90-100 m.