Deep-sea community diversity on the U.S. West Coast: eDNA profiles of deep-sea coral and sponge community diversity from the EXPRESS program

Understanding the basic relationship between fish communities and deep-sea coral communities is important for fisheries managers to assess impacts on these communities, monitor recovery, and identify key areas for protection. In 2018, environmental DNA (eDNA) and physical samples of deep-sea corals and sponges were collected at multiple sites along the west coast of the U.S. during the EXpanding Pacific Research and Exploration of Submerged Systems (EXPRESS) October cruise. A total of 95 coral and sponge samples, to be added to species voucher collections, and 27 eDNA samples were collected along the coast. Samples were collected in National Marine Sanctuaries, as well as in areas spanning recently proposed fisheries boundary changes. These samples establish important baseline information for previously unsurveyed areas, including areas of proposed management modification, and assist with the monitoring of recovery in areas closed since 2006. eDNA samples were assayed for coral, sponge, and fish species. The individual physical coral and sponge samples were sequenced and added to the sequence reference databases used for eDNA analyses. By sequencing amplicons for octocorals, fishes, and sponges from the same water samples and comparing to comprehensive reference libraries of west coast species, we have detected a wide range of species in diverse communities. Analysis of eDNA assists with detection of species that are small or not in the immediate visual range of the ROV. Using these methods, we have begun to better characterize patterns of biodiversity associated with deep-sea coral communities.