An oil rig explosion off the coast of Louisiana killed eleven workers on April 20, 2010. The world then looked helpless when BP oil spilled into the Gulf of Mexico for 87 days, killing millions of marine animals.
Dolphins that have survived one of the worst environmental disasters ever seem to be suffering the effects over a decade later.
Comparing numbers of common sharp dolphins (Tursiops truncatus) of Barataria Bay in Louisiana that lives within an area where oil is visible from numbers from Sarasota Bay in Florida, which has not been exposed to severe pollution, researchers have found that between health differences still exist.
Previous studies have already revealed the short-term effects of oil spills on Barataria Bay dolphins, including unusual adrenal function, lung disease, impaired reproduction, immune system problems and reduced survival. Dolphins living in the area only shed live calves 19 percent of the time.
Oil dolphin swimming in North Barataria Bay. (Louisiana Department of Wildlife and Fisheries)
Analyzing print samples from 34 Barataria Bay dolphins, University of Connecticut veterinary scientist Sylvain De Guise and colleagues found deficiencies in the immune system in 2018 similar to those found in the population in 2011. They then performed laboratory tests on dolphin and mouse cells to determine the presence of oil. it can promote these conditions.
“The parallelism between results in dolphins revealed after the Deepwater Horizon spill and laboratory mice exposed to oil was impressive and helped to raise the weight of evidence between oil exposure and specific effects on oil. the immune system, “De Guise explained.
Both the mice exposed to oil and the dolphins had increased T lymphocyte (white blood cell) proliferation and more cells that suppress the immune system – T regulatory cells. those cells prevent autoimmune diseases.
Although immunological changes were observed in dolphins exposed to other pressures, such as toxins under algal blooms, the pattern of changes was different from those seen in Barataria Bay dolphins.
Studies in rodents have linked a link between changes such as the immune system and increased susceptibility to disease. De Guise’s team showed that these protective differences could be passed on from rodents exposed to oil contamination to their young. And since the changes weren’t just present in the older dolphins, the team is concerned that these deficiencies are being passed on through generations of dolphins.
However, there is another possible explanation for this though.
“It is possible that there is an ongoing exposure to Deepwater Horizon oil that may not have been completely removed from the Barataria Bay ecosystem,” the team wrote in their paper.
Samples of Barataria Bay bog sediments showed that oil density was still 10 times higher than it was before the spill, eight years later. More research will be needed to find out exactly what is happening.
Researchers are concerned that the long-term effects of oil spills may not be limited to dolphins. Little is known yet about the health consequences of other long-lived species such as turtles. Immunosuppressive effects have been reported in humans who have worked to clean up oil spills, suggesting a common response to oil exposure over mammals.
“The long-term effects and the potential for multi-generational effects raise serious concerns for the recovery of dolphin numbers after the outbreak,” said De Guise.
This research was published in Environmental Toxicology and Chemistry.