Research results published today in a special-themed issue of Endangered Species Research, document the unprecedented and long-term environmental impacts of oil exposure to marine mammals and sea turtles after the 2010 Deepwater Horizon (DWH) oil spill.

Overall, experts concluded that the Deepwater Horizon oil spill killed thousands of marine mammals and sea turtles, and contaminated their habitats. The National Marine Mammal Foundation’s Dr. Lori Schwacke and Dr. Cynthia Smith are lead authors on two of the research articles and the NMMF scientists served key roles in the investigation of injuries to marine mammals in the Gulf.

“Our research continues to paint a troubling picture of dolphin health as a result of the Deepwater Horizon disaster seven years ago,” said Dr. Smith. “These publications summarize the work that was done as part of the Natural Resource Damage Assessment, but there’s a long road ahead for recovery of the dolphin populations. Continued monitoring of their health is going to be critical.”

Distinguished as the largest offshore oil spill in U.S. history, the April 20, 2010 Deepwater Horizon incident released 134 million gallons of oil into the Gulf over a period of 87 days, fouling 1,300 miles of shoreline along five states. The spill resulted in significant environmental damage over a large area of the Gulf of Mexico and affected numerous species including bottlenose dolphins.

The research findings reported by Dr. Smith came from veterinary assessments on dolphins in Barataria Bay and Mississippi Sound, and indicate that recovery of the dolphins health has been slow. Even four years post-spill, the dolphins had a high prevalence of lung disease and showed impaired stress response. Also reported in the research released today are results of photographic surveys conducted to monitor the dolphins over the years following the spill, which found reduced survival rates and low reproductive success. Marine mammal researchers concluded that bottlenose dolphins killed by these adverse health effects contributed to the largest and longest marine mammal unusual mortality event ever recorded in the Gulf of Mexico.

The continued poor health of individual dolphins will mean declines in Gulf of Mexico dolphin populations. An analysis to predict the impacts at the population level, led by Dr. Schwacke, indicates that the population in Barataria Bay will be reduced by 50% within the decade following the spill and that full population recovery will take nearly 40 years. Because recovery of this slow-growing, long-lived species will take decades, extensive long-term monitoring and restoration are required.

A Gulf of Mexico Research Initiative (GoMRI) grant is enabling NMMF researchers to continue to study Barataria Bay dolphins to better understand why so many of those dolphins are failing to reproduce. Their ongoing research may help to inform restoration efforts in the Gulf, and will also help to predict impacts and recovery timelines for marine mammal populations involved in future oil spill events.

The Endangered Species Research special issue contains more than 20 scientific studies detailing the work of NOAA experts and partners to assess and quantify the adverse impacts from the Deepwater Horizon oil spill on these species, which are protected under U.S. laws such as the Endangered Species Act and the Marine Mammal Protection Act. It presents a synthesis of more than five years of data collection, analysis, and interpretation.

Findings from these research studies, in addition to other studies on other parts of the ecosystem, formed the basis of the natural resources damage assessment settlement with BP for up to $8.8 billion, of which $307 million will be allocated specifically to the recovery of marine mammals and sea turtles. The Endangered Species Research special issue is a historic compilation of information from both sea turtles and marine mammals impacted by the Deepwater Horizon oil spill, presented in a peer-reviewed scientific publication.

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