USING SHORT-LIVED RADIONUCLIDE GEOCHRONOLOGY TO QUANTIFY BENTHIC FORAMINFERA RESPONSE TO THE BP OIL BLOWOUT

A suite of sediment cores were collected from the northeastern Gulf of Mexico in response to the British Petroleum oil blowout from August 2010 to April 2012. The coring sites have been sampled several times over the past two years using a paired coring method. One core was used to determine the abundance of benthic foraminifera (including Cibicidoides sp., Uvigerina sp., and Bulimina sp.) and the other utilized for a high resolution geochronology based on short-lived radionuclides (²¹⁰Pb and ²³⁴Th). This approach has allowed for time series (month-to-month) analysis of foraminifera abundance (by volume) in response to potential direct hydrocarbon toxicity and hypoxia due to the large amount of organic matter deposited during the blowout event. Preliminary results show a significant reduction of all benthic foraminifera genera in the surface (0-1cm) of the December 2010 cores, which is synchronous with a decrease in grain size of the bulk sediments. The dominance of Uvigerina sp. and Bulimina sp. at certain sites decreases as Cibicidoides sp. abundance increases significantly during the transition between the December 2010 cores and the February 2011 cores. There is also a significant, overall increase in benthic foraminiferal abundance during the December 2010 to February 2011 transition. This evidence suggests that the effected benthic foraminifera communities began to recover between December 2010 and February 2011. The changes in abundance of benthic foraminifera coupled with short-lived radionuclide geochronology 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 BP oil blowout.