Deep-Sea Benthic Footprint of the Deepwater Horizon Blowout

Citation: Montagna PA, Baguley JG, Cooksey C, Hartwell I, Hyde LJ, et al. ( Deep-Sea Benthic Footprint of the Deepwater Horizon Blowout Paul A. Montagna 0 Jeffrey G. Baguley 0 Cynthia Cooksey 0 Ian Hartwell 0 Larry J. Hyde 0 Jeffrey L. Hyland 0 Richard D. Kalke 0 Laura M. Kracker 0 Michael Reuscher 0 Adelaide C. E. Rhodes 0 Fabiano Thompson, Universidade Federal do Rio de Janeiro, Brazil 0 1 Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, Corpus Christi, Texas, United States of America, 2 Department of Biology, University of Nevada-Reno, Reno, Nevada, United States of America, 3 National Centers for Coastal Ocean Science, National Oceanic and Atmospheric Administration, Charleston, South Carolina, United States of America, 4 National Centers for Coastal Ocean Science, National Oceanic and Atmospheric Administration , Silver Spring, Maryland , United States of America The Deepwater Horizon (DWH) accident in the northern Gulf of Mexico occurred on April 20, 2010 at a water depth of 1525 meters, and a deep-sea plume was detected within one month. Oil contacted and persisted in parts of the bottom of the deep-sea in the Gulf of Mexico. As part of the response to the accident, monitoring cruises were deployed in fall 2010 to measure potential impacts on the two main soft-bottom benthic invertebrate groups: macrofauna and meiofauna. Sediment was collected using a multicorer so that samples for chemical, physical and biological analyses could be taken simultaneously and analyzed using multivariate methods. The footprint of the oil spill was identified by creating a new variable with principal components analysis where the first factor was indicative of the oil spill impacts and this new variable mapped in a geographic information system to identify the area of the oil spill footprint. The most severe relative reduction 2 of faunal abundance and diversity extended to 3 km from the wellhead in all directions covering an area about 24 km . Moderate impacts were observed up to 17 km towards the southwest and 8.5 km towards the northeast of the wellhead, covering an area 148 km2. Benthic effects were correlated to total petroleum hydrocarbon, polycyclic aromatic hydrocarbons and barium concentrations, and distance to the wellhead; but not distance to hydrocarbon seeps. Thus, benthic effects are more likely due to the oil spill, and not natural hydrocarbon seepage. Recovery rates in the deep sea are likely to be slow, on the order of decades or longer. - Funding: Sample collection during cruises on board R/V Gyre and R/V Ocean Veritas during the Response phase was funded by BP and NOAA as part of the DWH Response effort through funds from BP under the direction of the DWH Unified Area Command (UAC). Sample analysis and production of this paper was funded in part by contract DG133C06NC1729 from the National Oceanic and Atmospheric Administration (NOAA) via subcontract 1050-TAMUCC from Industrial Economics as part of the Deepwater Horizon Oil Spill Natural Resource Damage Assessment (NRDA). Christopher Lewis (Industrial Economics, Inc.) and Rob Ricker (NOAA) reviewed and commented on earlier versions of the manuscript. The views expressed herein are those of the authors and do not necessarily reflect the views of NOAA or any of its personnel. The study design and scope of work for the present deep-water/soft-bottom benthic study was approved jointly by representatives of the DWH NRDA Trustees and BP; neither party had a role in the corresponding sample processing, data analysis, decision to publish, or preparation of the manuscript. Pre-approval to submit the manuscript for publication was provided by representatives of the NRDA Trustees. Competing Interests: The authors have the following interests. Sample collection during cruises on board R/V Gyre and R/V Ocean Veritas during the Response phase was partly funded by BP as part of the DWH Response effort through funds from BP under the direction of the DWH Unified Area Command (UAC). Christopher Lewis (Industrial Economics, Inc.) reviewed and commented on earlier versions of the manuscript. The study design and scope of work for the present deep-water/soft-bottom benthic study was approved jointly by representatives of the DWH NRDA Trustees and BP. There are no patents, products in development or marketed products to declare. This does not alter the authors adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors. The Deepwater Horizon (DWH) accident in the northern Gulf of Mexico occurred on April 20, 2010 at a water depth of 1525 meters, in Mississippi Canyon Block 252, releasing an estimated 4.6 million barrels ( = 193 million U.S. gallons, or 731 million liters) of oil to the Gulf of Mexico through July 15, 2010 [1]. While oil-budget estimates indicate a majority of the oil had been removed by cleanup operations and other natural mechanisms [2], up to 35% of the hydrocarbons were trapped and transported in persistent deep-sea plumes [3]. Thus, the DWH blowout actually presents two incidents: the familiar buoyant oil spill with surface effects of short residence times, and the novel deepwater plume with chronic subsurface effects that suppress population recovery of exposed animals [4]. In addition, there were likely mid-water impacts to plankton and a variety of mid-water species. Oil in the deepwater plume was transported to deepwater sediments via multiple pathways, e.g., direct sinking of oil, adsorption of small oil droplets (alone or mixed with dispersant) onto suspended organic and inorganic particles in marine snow, incorporation into sinking copepod fecal pellets in either surface or sub-surface layers, onshore-offshore transport of oil-laden particles, sinking of heavier oil by-products resulting from the burning of oil, or settling of oilmud complexes resulting from the injection of drilling muds during top-kill operations [5]. Heavy metals such as barium are components of drill cuttings, drill fluids, and other containment fluids commonly used during offshore oil-drilling operations [6,7] and were likely released and deposited to the bottom during the blowout event. Contaminants transported to the seafloor may pose risks to benthic fauna, particularly those living within or in close association with bottom substrates and unable to avoid exposure due to their relatively sedentary existence. Potential ecosystem service losses are of concern because these fauna serve vital functional roles in the deep-sea ecosystem including biomass production, sediment bioturbation and stabilization, organic matter decomposition and nutrient regeneration, and secondary production and energy flow to higher trophic levels [8,9]. In many places, the deep-sea benthos represent important reservoirs of marine biodiversity [10,11,12,13]. High benthic species diversity has been reported for the Gulf of Mexico with a maximum on the mid to u (...truncated)