Quantitative Habitat Characterization and Benthic Assemblage Structure of Deep-Water Scleractinian Reefs Off Eastern Florida

Eight deep-water coral sites were surveyed in November 2005 during 11 dives with the Johnson-Sea-Link submersible along the eastern continental margin of Florida from St. Augustine to Miami. Sites included unconsolidated sediment/coral bioherms, rocky lithoherms and the Miami Terrace escarpment. Photographic transects using high-resolution video and digital still images documented at each site. Observations were made over a depth range of 282-871 m. In situ temperatures ranged from 6 to 9°C. We examined 31 video transects and extracted over 2500 images for habitat characterization and quantitative analyses of percent coverage by substrate type and densities of major macrobenthic assemblage components using the Coral Point Count software (CPCe). All organisms larger than ~10 cm in each image were identified to the lowest possible taxonomic level. Substrate categories included living and dead standing coral, coral rubble, sediment, rock rubble, and hard substrate (e.g., pavement, boulders). The branching azooxanthellate scleractinian corals Lophelia pertusa and Enallopsammia profunda dominated five and six sites, respectively. The percentage of live coral varied among sites, regardless of the dominant species in that area. Sites dominated by L. pertusa showed greater accumulation of sediment, while E. profunda was most often associated with lithoherms, though both species were observed in both habitats. Distributions of corals and other organisms were related to depth, bottom topography and physical environmental conditions. Associated taxa included Madrepora oculata (Scleractinia), Keratosis flexibilis and Plumarella pourtalesii (Octocorallia), Stylasteridae, and numerous Hexactinellida and Demospongiae (e.g., Phakellia sp., Pachastrella sp., Aphrocallistes sp. and Heterotella sp.). The results will be applicable to managers in developing plans for conservation and protection of these fragile deep-water resources.