Comparison of Ridge Scarp Edge Geomorphology and Associated Benthic Habitats on the Southeast U.S. Continental Margin

Elizabeth Bieri, College of Charleston, Department of Biology, Charleston, SC, United States and Leslie Sautter, College of Charleston, Geology and Environmental Geosciences, Charleston, United States
As part of the East Coast Mapping Expedition (EX1403) in 2014 and the Windows to the Deep expeditions in 2018 and 2019 (EX1806 and EX1903), scientists from NOAA’s Office of Ocean Exploration Research (OER) aboard the NOAA Ship Okeanos Explorer mapped portions of the Blake Plateau on the southeast U.S. continental margin using multibeam sonar data. During expeditions EX1806 and EX1903, the ROV Deep Discoverer conducted multiple dives on the edges of at least seven ridge scarps and collected high definition video of deep-sea coral habitat. This study concentrates on the ridge scarp edges present on the Stetson Mesa, a feature located on the western Blake Plateau with depths ranging from 600 to 900 m. Situated under the Gulf Stream, water temperature, current velocity and nutrient abundance are high in this area. High resolution bathymetry and subsequent exploration has revealed hundreds of mound features, suggesting that these mounds may well host significant deep-sea coral populations. This study focuses on the geomorphologic features referred to as ridge scarp mounds and examines them as potentially favorable habitat for benthic communities, including deep-sea corals. Ridge scarp mound features within the Stetson Mesa were surveyed to understand the relationships between geomorphology and associated biota. Findings were compared to ridge scarps lacking mounds in the Central Plateau and the Richardson Hills region of the Blake Plateau, both of which are located northeast of the mesa with depths ranging from 700 to 900 m. Footage from ROV dives was used to compare resident biota in each of the three study sites. Recognizing types of morphological features that promote deep-sea coral growth is critical to assessing potential distribution of organisms on the Blake Plateau as well as managing and protecting their essential habitats.