Red Crabs as Sentinel Organisms in Exposure of Deep-Sea Benthos to Macondo Oil Following the Deepwater Horizon Oil Spill

The Deepwater Horizon (DWH) oil spill was unique because unlike most oil spills, a substantial fraction of the released oil was deposited on deep-sea floor as both particulate oil close to the Macondo well and as oily floc further from the well. In late 2010/2011 and in 2014, benthic macrofauna, including large populations of the deep-sea red crab (Chaceon quinquedens), were collected from the deep seafloor to determine if there was forensic evidence for their exposure to the spilled Macondo oil. In this study, polycyclic aromatic hydrocarbons and biomarkers (triterpane and steranes) were measured in more than 1700 dissected red crab tissue samples, in order to assess the concentrations and distributions (chemical fingerprint) of any oil present within the tissues. Results show that red crabs clearly were exposed to Macondo oil from the DWH oil spill—and as such can be considered as sentinel organisms for oil exposure in deep benthic environments. Specific results included (1) among various tissue types studied, the red crab hepatopancreas provided the most sensitive and diagnostic chemical fingerprints by which to assess exposure of these animals, (2) the highest exposures of red crabs to Macondo oil in 2010/2011 occurred closest to the well although exposures up to 14 km southwest of the well were identified, (3) detection of Macondo oil residuals in red crabs was consistent with spatial distribution of spill-impacted deep-sea sediments, and (4) exposures were lower in 2014 but still recognized, particularly within the more recalcitrant biomarkers.