Decades after the Deepwater Horizon oil spill, local dolphins are still suffering

An oil rig explosion off the coast of Louisiana killed eleven workers on April 20, 2010. The world then watched helplessly as BP oil spurted into the Gulf of Mexico for 87 days, killing millions of marine animals. .

The dolphins who survived one of the worst environmental disasters of all time still appear to be suffering the effects more than a decade later.

Comparison of populations of bottlenose dolphins (Tursiops truncatus) from Barataria Bay in Louisiana who live in the oil exposure area of ​​people in Sarasota Bay in Florida, who have not been exposed to severe pollution, the researchers found that there are still disturbing health differences between them.

Previous studies have already revealed the short-term impacts of the oil spill on dolphins in Barataria Bay, including abnormal adrenal function, lung disease, impaired reproduction, immune system problems and reduced survival. Dolphins living in the spill area only gave birth to live calves 19 percent of the time.

Oiled dolphin swimming in the northern bay of Barataria. (Louisiana Department of Wildlife and Fisheries)

Analyzing tissue samples from 34 Barataria Bay dolphins, University of Connecticut veterinary scientist Sylvain De Guise and colleagues found immune system deficiencies in 2018 similar to those found in the population in 2011. They then performed lab tests on cells from dolphins and mice to confirm whether exposure to the oil can trigger these conditions.

“The parallel between the findings in dolphins exposed from the Deepwater Horizon spill and laboratory mice experimentally exposed to oil was impressive and really helped to establish the weight of evidence between oil exposure and specific effects. on the immune system, ”De Guise explained.

Mice exposed to the oil and dolphins had an increased proliferation of T lymphocytes (white blood cells) and more cells that suppress the immune system – regulatory T cells. These cells usually prevent autoimmune diseases.

Although immunological changes were also seen in dolphins exposed to other stresses, such as toxins from algae blooms, the pattern of changes was different from that seen in dolphins in Barataria Bay.

Studies in rodents have previously linked these changes in the immune system to increased susceptibility to disease. De Guise’s team showed that these immune differences could also be transmitted by rodents exposed to oil pollution to their young. And since the changes weren’t just present in older dolphins, the team is concerned that these impairments are passed down through generations of dolphins.

There is, however, another potential explanation for this.

“It is possible that there is continued exposure to Deepwater Horizon oil that may not have been completely removed from the Barataria Bay ecosystem,” the team wrote in their article.

Samples of sediment from the marshes of Barataria Bay showed that the oil concentrations were still 10 times higher than before the spill, eight years later. More research will be needed to determine exactly what is going on.

Researchers fear that the long-term effects of oil spills will be limited to dolphins. We still know little about the long-term health effects of other species like turtles. Immune effects have also been reported in humans who have worked to clean up oil spills, suggesting that there is a common response to oil exposure in mammals.

“The long-term effects and the potential for multigenerational effects raise significant concerns for the recovery of dolphin populations after the spill,” De Guise said.

This research was published in Environmental toxicology and chemistry.