Seafloor Mapping for Predicting Deep-Sea Coral Habitat, Southeast U.S. Continental Margin

Mikayla Drost and Leslie Sautter, College of Charleston, Geology and Environmental Geosciences, Charleston, SC, United States
During two Windows to the Deep expeditions in 2018 and 2019, the NOAA Office of Ocean Exploration and Research (OER) collected multibeam sonar data and high definition video of the seafloor off the southeast U.S. coast. These expeditions sought to gather critical baseline data on poorly understood areas of the continental margin where deep-sea coral habitats might occur. High definition video collected by the ROV Deep Discoverer was used to ground truth bathymetric surfaces generated from multibeam sonar data obtained from the NOAA Ship Okeanos Explorer. Utilizing the high-resolution bathymetric data collected by NOAA OER over the last two years, maps of areas known to host deep-sea corals were created. Two types of coral, the stony coral Lophelia pertusa and several species of bamboo corals (Family Isididae), were examined specifically. Their habitats are described and compared using bathymetric and in situ video data. This study focuses on several areas off Florida, Georgia, and South Carolina, where study sites range in depth between 700 to 900 m, 1200 to 1300 m, and 1600 to 1800 m. Sites are predominately located in areas directly under or highly influenced by the Gulf Stream. Previous work revealed little to no consistent association among slope, backscatter intensity and the presence of L. pertusa, and instead concluded that geomorphology is a better way of identifying potential habitat. Little is known about where bamboo corals are likely to be found, and their association with L. pertusa, two of the primary motivations behind this study.

High resolution video footage from the ROV Deep Discoverer was also used to identify key types of coral in various habitats. Dive track information was translated onto bathymetric surface maps. These data were used to examine backscatter intensity, slope, and the general geomorphology of the habitat areas preferred by both bamboo coral and L. pertusa. Habitat characteristics were subsequently compared to better understand the specific conditions in which these deep-sea corals are likely to thrive. As more information is collected and understood about the conditions favored by deep-sea corals, scientists can better inform the government and fisheries on how to protect and manage these vital areas.