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How the Deepwater Horizon Oil Spill is Affecting Bottlenose Dolphins a Decade Later

The Deepwater Horizon Oil Spill occurred in 2010 and was the largest oil spill in U.S. history. Though it was an incredibly traumatic event, it provided a very important research study that covers the dangerous effects of exposure to toxic chemicals and how living near oil spills can affect the short and long term health of animals and people.

In this webinar, Lori Schwacke, Cynthia Smith, and Len Thomas discussed the health and population trends of bottlenose dolphins in Barataria Bay. The NOAA conducted a Natural Resource Damage Assessment (NRDA) between 2010 to 2015 to look at the effects of the oil spill. The NRDA studied stranded and dead dolphin tissue that gave insight into how dolphins were affected. The assessment conducted physical examinations, photo-ID studies, and remote biopsy sampling to assess the long term effects and reproductive rates of dolphins.

In order for the NRDA to be successful, a baseline needed to be estimated so that they could compare data from after the oil spill to before. When an oil spill is occurring dolphins can absorb oils and other toxins through inhalation, aspiration, and ingestion. They are also considered to be more susceptible to the toxicity because the toxins go straight to their lungs and when they take deep breaths of air to dive deep the toxins stay in their body for a long period of time. The bottlenose dolphins in Barataria Bay in 2011 were five times more likely to have moderate to severe lung disease than dolphins who were not exposed; this was determined by the analysis of bottlenose dolphin cohorts in Sarasota Bay and Barataria Bay.

The lung scores in dolphins between Barataria Bay and Sarasota Bay after the oil spills were significantly different and confirmed that lung disease in dolphins was amplified by the oil spill.

It was proposed by NOAA that it would take approximately 10 years for the dolphins in the area to recover, but the 50 year Deepwater Horizon Restoration Project will affect that process. The restoration project was put into effect to clean up the oil and restore the natural habitat by directing fresh water from the Mississippi to be released into the bay to restore the wetlands, but this process was incredibly harmful to dolphins; freshwater causes salinity to decrease making it inhabitable and since it is unlikely that they will move it will result in the dolphins experiencing a vast amount of health issues. As it will now take decades for the dolphin population to recover, continued examination is crucial.


Health trends and population trajectory for Bataria Bay common bottlenose dolphins [Video file]. (2021, July 15), from


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