Tracking Macondo Oil in the Marsh: Sampling directly via sediment and indirectly via ants

On April 20, 2010, the Macondo well in Mississippi Canyon 252 blew and the well gushed oil uncontrollably into the sea and subsequently into the saltmarsh. Aromatics were measured and found to increase until May 2011. In Sept 2012, Hurricane Isaac remobilized oil in the marsh further increasing aromatics once again and oiled areas of marsh that were previously not contaminated with Macondo oil. Over the course of the next year, monthly samples were taken and the aromatics decreased. Also, a large number of extracted oil samples emerged in the marsh that matched the Macondo oil, but differed significantly from the original patterns seen which we started calling "Pattern A" and "Pattern B." Additionally, in 2013 an uptick in aromatic compounds was observed at previously-oiled sites and lesser so at some previously-unoiled sites. Associated with this increase in aromatics was a shift from mostly Pattern A oil to more Pattern B oil or a combination of Pattern AB.

Previously, we've shown that the ants in the marsh are intimately connected to the terrestrial food web and that they are good indicators of the presence of stressors that affect food availability for vertebrates such as fish and birds. Initially populations of ants survived the oiling of the marshes but the population crashed in the summer of 2011 in response to the decreased food availability in the marsh. We started to see recovery of ants in the oiled areas in August 2012, but the populations were annihilated by hurricane Isaac. The ants largely recovered in the unoiled plots, but not in oiled plots in 2013, which matches the uptick in the aromatic compounds measured at the same sites. In 2015, we started to measure recovery of the ant population in the oiled areas but lack hydrocarbon data at this time to associate with the recovery.