DOCUMENTING THE SPATIAL AND TEMPORAL RESPONSE OF BENTHIC FORAMINIFERA FOLLOWING SUBSURFACE OIL RELEASES IN THE GULF OF MEXICO

A series of sediment cores collected from the Gulf of Mexico (2010-2014) were used to assess the spatial and temporal impacts on the benthos, quantify the recovery of benthic foraminiferal (BF) community and shell chemistry (δ¹³C) following the Deepwater Horizon (DWH) event. A significant decline in BF density (80-93%) and diversity recognized since 2010 has been attributed to both a 2-3-fold increase in polycyclic aromatic hydrocarbon concentrations and increasing reducing conditions in surface sediments. At certain sites, a recovery in density occurred in late 2011, while at other sites density did not recover until 2012. Independent of location, the δ¹³C record of BF carbonate showed a marked depletion in 2010 that has further intensified through 2012. This suggests that BF not only incorporated petroleum carbon into their shells directly following the DWH event, but that they were continually respiring a petroleum carbon source for more than two years afterwards. Using both δ¹³C and Δ¹⁴C mass balance approaches, 1-2.5% of total respired carbon assimilated into BF carbonate from 2010 to 2012 was comprised of petroleum carbon. BF community change and trophic implications over this time-series will be discussed and compared to the record of recovery in the Southern Gulf of Mexico following the IXTOC event (1979). This continuing research identifies specific biological responses to physical and chemical changes in the sediments and identifies benthic community recovery rates following a deep-water petroleum release.