Marine Mammals and Respiration: Evidence of Poor Pulmonary Health in Bottlenose Dolphins Following the Deepwater Horizon Oil Spill

Abstract

ABSTRACT The Deepwater Horizon (DWH) disaster resulted in large-scale contamination of bays, sounds, and estuaries in the northern Gulf of Mexico (GoM), home to multiple stocks of bottlenose dolphins. Inhalation, direct aspiration, ingestion with subsequent aspiration, and dermal absorption of oil and its toxic components were all considered possible routes of exposure for dolphins living within the oil spill footprint. To determine if dolphins were adversely impacted, capture-release health assessments were performed in heavily-oiled Barataria Bay (BB), Louisiana, and in Sarasota Bay (SB), Florida, a comparison site with no DWH oil contamination. Initial studies were conducted as part of a Natural Resource Damage Assessment (2011–2014), with follow-on studies supported by the Gulf of Mexico Research Initiative (2016–2018). To specifically evaluate pulmonary health, transthoracic ultrasound techniques previously developed for managed dolphins were applied to wild dolphins. Results showed that BB dolphins were ~5 times more likely to have moderate to severe lung disease than SB dolphins in 2011, the year following the spill. Concurrent pathology investigations of dead dolphins in the northern GoM reported similar pulmonary findings. In 2013 and 2014, moderate to severe lung disease persisted among BB dolphins, and remained elevated relative to the prevalence at the SB comparison site. More recent live animal health assessments (2016–2018) showed long-term persistence and potential worsening of moderate to severe lung disease in BB dolphins, specifically in animals alive during the oil spill (prevalence of 0.20, 0.35, and 0.55 in 2016, 2017, and 2018, respectively). Long-term monitoring of dolphin populations is critical to fully understand the potential for and timeline of individual and population recovery from the impacts of a large-scale oil spill event, as well as the cost-benefit trade-offs for restoration activities. In particular, BB dolphins provide valuable insight into the long-lasting effects of oil and oil-related contaminants on animal, human, and ecosystem health.