THE CHARACTERIZATION AND SEDIMENTATION DYNAMICS OF THE PELAGIC SEDIMENT SUPPLY TO THE DEEP SEA CORAL ECOSYSTEM (DSCE) OF THE EAST FLORIDA LOPHELIA REEF

Biogenic ooze, which is carbonate sediment composed of at least 30% skeletal remains of marine organisms, covers an extensive area of the Blake Plateau located on the continental shelf off the east coast of Florida. The plateau includes a region known as the east Florida Lophelia reef, which contains a 222 km belt of numerous deep-sea coral mounds that grow to heights of over 168 m. These mounds contain branching corals that baffle pelagic sediment and develop into large bioherms that provide habitat for a countless number of deep-sea organisms. Research pertaining to the characterization and sedimentation dynamics of the biogenic ooze precipitating on the east Florida Lophelia reef region is scarce. Sediment samples were collected in situ from a submersible, at a depth of 782 m from gullies between Lophelia coral mounds on the unconsolidated surface of the east Florida Lophelia reef region. Microscopic examination of the samples resulted in the identification of 15 different thecosome pteropod species (holoplanktonic mollusks) and an overall sediment composition consisting of 85.6% pteropods, 8% forams, 3.1% gastropods, 2.3% bryozoan/coral fragments, and less than 1% of other microfossils (heteropods, echinoids, scaphopods, etc.). This unique assemblage of well-preserved microfossils is classified as pteropod ooze (>25% pteropods). Styliola subula is the most abundant pteropod species comprising 46% of the sediment. In 1965 the Deep Sea Drilling Project (DSDP) extracted drill cores from the Blake Plateau that revealed a surficial unit of post-Miocene foraminiferal-pteropod calcilutite up to 6.1 m thick, indicating ongoing ooze sedimentation in this region. Paull et al. (2000) has described core samples retrieved from deep-sea coral mounds in an adjacent region known as the Florida-Hatteras slope. Their study found biogenic sediment fill containing pteropods that act as cement for deep-sea lithoherm growth and the discovery of an exposed benthic substrate defined as a ‘pteropod crust’. The samples analyzed for our study reveal a sediment composition of planktonic origin depositing in the east Florida Lophelia reef region. This suggests that the pteropod ooze may be the basis for coral mound development in Deep-Sea Coral Ecosystems (DSCE’s).