Characterizing Geomorphology of Connected Coral Mounds by Gulf Stream Influence on the Lower Stetson Mesa off the Southeast U.S. Coast.

The Stetson Mesa is an incredibly biodiverse region of great interest to NOAA and the scientific community, because its close proximity to the Gulf Stream allows for high-current environments and habitats of benthic communities. The mesa is located on the western portion of the Blake Plateau on the continental margin off the Southeastern U.S. coast, where water depths range from approximately 600 to 900 m. NOAA’s Office of Ocean Exploration and Research (OER) conducted seafloor mapping and ROV dives from aboard the NOAA Ship Okeanos Explorer during Windows to the Deep 2019: Exploration of the Deep-sea Habitats of the Southeastern United States, EX1903. While mapping this area, the ROV Deep Discoverer was sent on multiple dives to collect high-definition video on the seafloor geomorphology and benthic communities. This study focuses on two portions of the lower Stetson Mesa, at sites referred to as Canaveral Deep and the Stetson Mesa South where numerous mounds, made of deep-sea coral communities built over time on top of stony coral rubble, were mapped. The type of coral mounds examined are classified as ‘connected mounds’ as they are adjacent to one another and aligned across the flow of the Gulf Stream’s current. These connected mounds and their many features are believed to be influenced by the Gulf Stream and its warm, nutrient- and food-rich water. The purpose of this study is to compare and characterize this type of mound at the two study sites which both lie between water depths of 700 and 800 m, directly under the main Gulf Stream axis. Surfaces obtained from multibeam sonar data were used to examine bathymetry, slope and backscatter intensity. Results on the distribution of deep-sea coral connected mounds will be presented, including potential sites for other deep-sea coral habitats in the region.