Slow recovery of Barataria Bay dolphin health following the Deepwater Horizon oil spill (2013-2014), with evidence of persistent lung disease and impaired stress response

The 2010 Deepwater Horizon (DWH) disaster resulted in large-scale oil contamination of the northern Gulf of Mexico. As part of the Natural Resource Damage Assessment designed to investigate the potential impacts of the DWH oil spill, comprehensive health assessments were conducted on bottlenose dolphins Tursiops truncatus living in oiled bays (Barataria Bay [BB], Louisiana, and Mississippi Sound [MS], Mississippi/Alabama) and a reference bay with no evidence of DWH oil contamination (Sarasota Bay [SB], Florida). As previously reported, multiple health issues were detected in BB dolphins during 2011. In the present study, follow-on capture-release health assessments of BB dolphins were performed (2013, 2014) and indicated an overall improvement in population health, but demonstrated that pulmonary abnormalities and impaired stress response persisted for at least 4 yr after the DWH disaster. Specifically, moderate to severe lung disease remained elevated, and BB dolphins continued to release low levels of cortisol in the face of capture stress. The proportion of guarded or worse prognoses in BB improved over time, but 4 yr post-spill, they were still above the proportion seen in SB. Health assessments performed in MS in 2013 showed similar findings to BB, characterized by an elevated prevalence of low serum cortisol and moderate to severe lung disease. Prognosis scores for dolphins examined in MS in 2013 were similar to BB in 2013. Data from these follow-on studies confirmed that dolphins living in areas affected by the DWH spill were more likely to be ill; however, some improvement in population health has occurred over time.