--> Abstract: Deepwater Horizon: Coastal Ocean to Marsh Margin Sedimentary Impacts, by Kevin M. Yeager, Charlotte A. Brunner, Kevin B. Briggs, Patrick Louchouarn, Laodong Guo, Vernon Asper, Kimberly J. Schindler, Kevin M. Martin, Jeremy Prouhet, Nate Couey, and Carlo Fortner; #90124 (2011)

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AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Deepwater Horizon: Coastal Ocean to Marsh Margin Sedimentary Impacts

Kevin M. Yeager1; Charlotte A. Brunner1; Kevin B. Briggs2; Patrick Louchouarn3; Laodong Guo1; Vernon Asper1; Kimberly J. Schindler1; Kevin M. Martin1; Jeremy Prouhet1; Nate Couey4; Carlo Fortner4

(1) Marine Science, University of Southern Mississippi, Stennis Space Center, MS.

(2) Seafloor Sciences Branch, Naval Research Laboratory, Stennis Space Center, MS.

(3) Marine Sciences, Texas A&M University at Galveston, Galveston, TX.

(4) Geography and Geology, University of Southern Mississippi, Hattiesburg, MS.

Oil pollution can devastate seafloor and coastal margin environments by majorly disrupting biogeochemical processes. Oil can cause mass or selective mortality of benthic meio- and macrofauna, either directly by surface coating or hydrocarbon toxicity, or indirectly by overloading the system with organic carbon and driving enhanced microbial respiration. Additionally, reductions in benthic biomass will reduce physical mixing of the sediment by suppression of major bioturbators. Oil spilled in marine environments can be incorporated into sediments in several ways. Because much oil remains at the surface, it can be added directly to intertidal zone sediments by wave and tidal action. However, 10-30% of spilled oil can adhere to suspended particles, and sink to the seafloor, a process most active in particle-rich coastal waters like the Chandeleur Sound, the MS Sound, and the MS Bight. Emulsified oil can be ingested by filter feeders and the oil components added to bottom sediment with deposition of fecal pellets and lysed or senescent cellular materials. Finally, weathered tar balls can become dense enough to sink to the seafloor. Once weathered oil is mixed into anaerobic sediment, its rate of microbial decomposition slows dramatically. The oil can then linger in the subsurface for months to decades, adversely affecting benthic biota and their contributions to the environment.

This presentation will focus on the results of ongoing research which began in June, 2010 and is centered on understanding the impacts of oil on marine, near-shore and coastal sedimentary environments and corresponding benthic ecosystems. Research efforts have been focused on quantifying oil delivery to and distribution within sedimentary environments, measuring the resulting impacts on in-situ benthic communities, and assessing rates and pathways of oil degradation. Given the temporal and the spatial scales of the spill, sampled environments include the deep sea (abyssal plain, slope and shelf), the MS Sound, the Chandeleur Sound, island marshes of the Mississippi River delta and coastal marshes of both MS and LA. Sampling locations were chosen to maximize the likelihood that a range of oil-exposure levels could be measured. A wide-ranging and interdisciplinary suite of techniques have been brought to bear on these questions and include elements of sedimentology, organic geochemistry, benthic ecology, stable and radio-isotope geochemistry, and marine technology.