Benthic foraminiferal morphological response to the 2010 Deepwater Horizon oil spill

Abstract

The 2010 Deepwater Horizon (DWH) oil spill released 4.0 million barrels of petroleum into the Northern Gulf of Mexico (NGoM), causing a substantial Marine Oil Snow, Sedimentation and Flocculent Accumulation (MOSSFA) event. Benthic foraminifera have successfully been used as bioindicators of the event with an 80–93% decline in density coinciding with the oil spill, followed by a recovery period to a steady state within three to five years. Here we present the results of a size and morphological study of four species of benthic foraminifera which remained abundant through the DWH oil spill (Uvigerina peregrina, Brizalina subaenariensis var. mexicana, Bulimina marginata and Cassidulina teretis) to understand how different species were impacted and why such a loss in density occurred. Short-lived radioisotope dating distinguished the pre-DWH and post-DWH depth intervals from 2010 to 2015. The species exhibit shape changes in response to the oil and MOSSFA processes and the pre-DWH length/width ratios of Uvigerina peregrina and Brizalina subaenariensis var. mexicana are significantly different than post-DWH length/width ratios within the cores. Reduced oxygen levels were likely a long-term (3–5 years) driver of this shape change and enhanced organic carbon concentrations were a short-term (1–2 years) driver. This study demonstrated the importance of the benthic foraminiferal morphological response to the DWH oil spill and furthers our understanding of the strategies of taxa that occurred abundantly throughout the record.