Comparing Seabed Geomorphology at Several Methane Seeps Found Along the North Carolina – Virginia Margin

NOAA Office of Ocean Exploration and Research conducted multibeam bathymetric surveys of the southeast U.S. continental margin aboard the NOAA Ship Okeanos Explorer from May 30^th through July 12^th, 2019. The goal of the Windows to the Deep 2019 expedition (EX1903) was to collect information about previously unknown or poorly understood deepwater habitats along the southeastern United States. A number of the expedition’s dives were conducted to investigate active methane seep sites identified through multibeam analysis of the water column. The remotely operated vehicle (ROV) Deep Discoverer investigated two seep sites along intercanyon ridges of different depths at Bodie Island (360-415 m) and Norfolk Seep (1,600 m). ROV dive videos revealed some active methane bubbles, unknown chemosynthetic habitats with the presence of seep-associated bacterial mats, and sizable beds of the chemosynthetic mussel Bathymodiolus childressi. These mussels were observed growing on and around authigenic carbonate outcrops. Video and bathymetric data from the Pea Island seeps (328-511 m) explored during expedition EX1806 were compared with the Bodie Island seep site due to its proximity and similar depth. Multibeam sonar data collected during EX1903 and previous Okeanos Explorer mapping cruises were used to generate high resolution bathymetry, slope, and backscatter intensity surfaces to investigate the geomorphology, and characterize the methane seep sites at different depths.