Characterizing the Deep Sea Benthic Foraminifera Impact and Response to the Deepwater Horizon Blowout in the Northeastern Gulf of Mexico

Sediment cores were collected from the northeastern Gulf of Mexico to assess changes in deep-sea benthic foraminifera related to the Deepwater Horizon blowout, which occurred from April to July of 2010. Short-lived radioisotope geochronology (²¹⁰Pb and ²³⁴Th) and organic geochemical toxicity assessments were also made to relate changes in sediment accumulation rate and sediment toxicity levels with benthic foraminifera. Cores collected in December 2010 indicate a community-wide event characterized by a decrease in concentration and benthic foraminifera mass accumulation rate (BFMAR) in the surface 10 mm relative to the down-core mean in all benthic foraminifera. Cores collected in February 2011 document a site-specific response and possible community recovery. In the site closer to the wellhead (45 NM, NE) there is evidence of a recovery in the benthic foraminifera community in both the concentrations and BFMAR. However, the site farther afield (60 NM, NE) records a continued depletion event characterized by a further decrease in benthic foraminifera concentrations and BFMAR down to zero values. Among the many questions to address, [(1) the mechanism for the decline (anoxia, hydrocarbon toxicity, etc.), (2) the trophic implications and (3) the spatial extent of the decline] perhaps the most important is the determination of recovery time for the system. Further analysis of benthic foraminifera abundance from cores collected after February 2011 (September 2011 and August 2012) will address the pressing issue of how long it will take for the benthic communities to recover from an event such as the Deepwater Horizon blowout. The records of benthic foraminifera abundance coupled with short-lived radionuclide geochronology and organic geochemical toxicity has shown to be effective in documenting and quantifying the benthic community response and will continue to be a valuable tool in determining the long-term effects of the Deepwater Horizon oil blowout on a larger spatial scale.