Deepwater Horizon Oil Caused Gulf Dolphin Deaths – Study

A new study has conclusively determined that oil from the Deepwater Horizon disaster contributed to the unusually high number of dolphin deaths in Louisiana, Mississippi and Alabama between June 2010 and December 2012. Deaths in these states remain elevated, five years after the initial explosion.

The study shows that dolphin carcasses found in the oiled areas were far more likely to have lesions on their adrenal glands and lungs – symptoms consistent with oil exposure – compared to dolphins that stranded before the spill or in unaffected areas.

“These dolphins had some of the most severe lung lesions I have seen in the over 13 years that I have been examining dead dolphin tissues from throughout the United States,” said lead veterinarian on the study Dr. Kathleen Colegrove.

A dolphin swimming in oiled waters, 2010, in Barataria Bay, La. Photo: Louisiana Department of Wildlife and Fisheries/Mandy Tumlin.
A dolphin swimming in oiled water, 2010. Photo: Louisiana Department of Wildlife and Fisheries/Mandy Tumlin.
This is by no means the first study to indicate ongoing impacts from the disaster. The results of this new study are consistent with a 2013 study that found many live dolphins in heavily-oiled Barataria Bay, Louisiana were in had symptoms of oil exposure, such as adrenal disease and lung masses. Another study looking at the timing and location of the deaths suggested a connection to the Deepwater Horizon.

According to NOAA’s Dr. Teri Rowles, all these studies have “increasingly pointed to the presence of petroleum hydrocarbons as being the most significant cause of the illnesses and deaths plaguing the Gulf’s dolphin population. This study carries those findings significantly forward.”

Rowles noted that dolphins and whales may have been particularly susceptible to injury from inhalation of oil as they hold their breath for long periods.

And while much of the agency’s research has focused on bottlenose dolphins in coastal areas, NOAA’s scientists believe there is just as much reason to be concerned about dolphins and whales that live in deep water, closer to the wellhead.

As Dr. Rowles noted, “We’re also concerned and doing investigations on animals along the continental shelf and in the deep water, including all the [dolphins and whales] that were in the area exposed to the oil during the spill. …The concerns are still the same—or increased—because the location of the animals, depth of diving and numbers of animals in that area.”

BP responded to the study by denying its conclusions outright.

“This new federal study proves conclusively that BP is misleading the American people and puts the ‘smoking gun’ in BP’s hands, said NWF’s president and CEO Collin O’Mara said in a statement. “BP needs to quit misleading the American people, accept responsibility for its actions, stop dragging this out in court, and allow restoration to begin. The Gulf has waited long enough.”

Learn more about ongoing impacts to wildlife in our new report Five Years & Counting: Gulf Wildlife in the Aftermath of the Deepwater Horizon Disaster.

Take ActionTell BP to accept responsibility for its actions by paying its Clean Water Act fines! 

Alisha Renfro, NWF’s Mississippi River Delta coastal scientist, co-authored this blog post.