Comparison of Individual Deep-Sea Coral Mounds at Three Sites in Relation to Proximity to the Gulf Stream

As part of the Atlantic Seafloor Partnership for Integrated Research and Exploration (ASPIRE) campaign, the NOAA Ship Okeanos Explorer conducted two expeditions within the Blake Plateau. Located on the continental margin of the southeast United States, the Blake Plateau is a wide and relatively flat expanse of the continental slope extending off the coast from North Carolina down to Florida, with depths ranging from 600 to over 1800 m. During the expedition Windows to the Deep 2019: Exploration of the Deep Sea Habitats of the Southeastern United States (EX1903 Legs 1 & 2), bathymetric data were collected using multibeam sonar, and high definition videos were captured using the ROV Deep Discoverer. ROV dives examined previously unmapped areas along the Blake Plateau Knolls (754-826 m depth range) and within the Central Plateau (786-863 m), and explored deep-sea coral mounds found on the Stetson Mesa (770-805 m). Home to the site of the “Million Mounds” area, Stetson Mesa lies on the western edge of the Blake Plateau and is located approximately 160 km off the coast of and nearly parallel to Florida. The mesa sits directly beneath the Gulf Stream, which provides beneficial conditions in support of deep-sea coral communities. The stony coral form dense colonies which build atop each other over time to form bioherms, or mounds. A recent study classified these mounds into three categories: individual, connected and ridge-scarp. Bathymetric data gathered at the Blake Plateau Knolls, located approximately 330 km off the coast southeast of Savannah, revealed undiscovered individual mounds. EX1903 Dives 04 and 05 provided ground truth imagery in support of live coral communities. Three study sites within the Blake Plateau that contain examples of individual mounds at similar depths were selected, located within Stetson Mesa, the Central Plateau, and the Blake Plateau Knolls. Using bathymetry, slope, and backscatter intensity, this study compared the geomorphic characteristics of coral mounds and their resident communities within and outside the influence of the Gulf Stream’s primary axis.