Oceanographic drivers of deep-sea coral species distribution and community assembly on seamounts, islands, atolls, and reefs within the Phoenix Islands Protected Area

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Auscavitch, S. R., Deere, M. C., Keller, A. G., Rotjan, R. D., Shank, T. M., & Cordes, E. E. Oceanographic drivers of deep-sea coral species distribution and community assembly on seamounts, islands, atolls, and reefs within the Phoenix Islands Protected Area. Frontiers in Marine Science, 7, (2020): 42, doi:10.3389/fmars.2020.00042.The Phoenix Islands Protected Area, in the central Pacific waters of the Republic of Kiribati, is a model for large marine protected area (MPA) development and maintenance, but baseline records of the protected biodiversity in its largest environment, the deep sea (>200 m), have not yet been determined. In general, the equatorial central Pacific lacks biogeographic perspective on deep-sea benthic communities compared to more well-studied regions of the North and South Pacific Ocean. In 2017, explorations by the NOAA ship Okeanos Explorer and R/V Falkor were among the first to document the diversity and distribution of deep-water benthic megafauna on numerous seamounts, islands, shallow coral reef banks, and atolls in the region. Here, we present baseline deep-sea coral species distribution and community assembly patterns within the Scleractinia, Octocorallia, Antipatharia, and Zoantharia with respect to different seafloor features and abiotic environmental variables across bathyal depths (200–2500 m). Remotely operated vehicle (ROV) transects were performed on 17 features throughout the Phoenix Islands and Tokelau Ridge Seamounts resulting in the observation of 12,828 deep-water corals and 167 identifiable morphospecies. Anthozoan assemblages were largely octocoral-dominated consisting of 78% of all observations with seamounts having a greater number of observed morphospecies compared to other feature types. Overlying water masses were observed to have significant effects on community assembly across bathyal depths. Revised species inventories further suggest that the protected area it is an area of biogeographic overlap for Pacific deep-water corals, containing species observed across bathyal provinces in the North Pacific, Southwest Pacific, and Western Pacific. These results underscore significant geographic and environmental complexity associated with deep-sea coral communities that remain in under-characterized in the equatorial central Pacific, but also highlight the additional efforts that need to be brought forth to effectively establish baseline ecological metrics in data deficient bathyal provinces.Funding for this work was provided by NOAA Office of Ocean Exploration and Research (Grant No. NA17OAR0110083) to RR, EC, TS, and David Gruber

Biogeographic Patterns Among Deep-Sea Benthic Megafaunal Communities Across the Drake Passage (Southern Ocean)

The Southern Ocean has long been recognized as a biogeographic discontinuity for marine organisms. The Drake Passage, a region bounded by the South America shelf to the north and the Western Antarctic Peninsula to the south, represents a convergence of several biogeographic sub-regions, yet many benthic communities throughout the region remain poorly characterized. This work seeks to provide a survey and comparison of nine deep-sea benthic communities across the Drake Passage using recently collected seafloor imagery and environmental data from cruises in 2008 and 2011. Over one thousand images across nine sites were examined for species composition, megafaunal density, and seafloor substrate characteristics. Towed camera observations revealed substantial sponge and coral diversity and abundance among several sites throughout Burdwood Bank, Cape Horn, as well as two offshore seamounts. Sars and Interim Seamounts exhibited multiple unique assemblages of invertebrate faunas including cold-water corals, anemones, and sponges compositionally similar to adjacent shelf environments. Multivariate biogeographic analyses among megafaunal communities suggest bathymetric patterns consistent within major Southern Ocean water masses including Subantarctic Mode Waters, Antarctic Intermediate Waters, and Circumpolar Deep Waters. As a result of this exploratory assessment, seamounts should be a focus of further examination of benthic communities throughout the Southern Ocean to provide insight to the role that these features play in defining regional biogeographic patterns