After the Deepwater Horizon oil spill in 2010, dolphins living in the area had changes in the activity of genes that regulate lung tissue growth and immune system responses
Dolphins living off the coast of Louisiana during and after the massive Deepwater Horizon oil spill in 2010 have genetic changes that could serve as a “canary in the coal mine” for future disease, according to researchers who analysed the animals’ blood samples.
“[Gene expression] is a very, very sensitive indicator that can let us know something’s going wrong long before we see illness or deaths in the population,” says Jeanine Morey at GEL Laboratories in South Carolina, who worked at the National Marine Mammal Foundation at the time of the study.
The largest marine petroleum spill, the Deepwater Horizon disaster churned around 800 million litres of crude oil into the Gulf of Mexico after an oil rig sank in April 2010. The impacts on wildlife were staggering, with fish, birds and marine animals dying in huge numbers. But the long-term consequences of the spill on wildlife are less understood, which led Morey to investigate how common bottlenose dolphins (Tursiops truncatus) were faring.
She and her team analysed the health records and blood samples of 71 wild dolphins captured and released between 2013 and 2018. During hands-on exams, biologists assessed each animal’s physical health, including their heart and lung function, and performed ultrasounds on pregnant females.
The researchers lacked data on dolphins before the spill, so they compared more than 11,000 genes of individuals living in oil-impacted Barataria Bay, Louisiana, with those from dolphins living in Sarasota Bay, Florida, which was spared from the spill. Some of the Louisiana dolphins lived through the disaster, while others were born after.
The analysis revealed thousands of differences in gene expression in animals in the disaster region compared with those outside the affected area. The gene PRG3, which is linked to declining lung health in humans, was expressed 8.2 times higher in dolphins that lived through the disaster than in those born after. Morey notes that dolphins in the contamination zone that had lung issues documented in their physical exams were more likely to have disruptions in the genes that regulate the growth of new lung tissue. The researchers also found elevated expression of a collection of genes associated with immune responses in dolphins from the contaminated zone.
The greatest differences in gene expression were seen in animals studied in 2013, the date closest to the disaster.
While the researchers were able to draw preliminary links between changes in gene expression and physical health symptoms, they caution that their sample size is small. They also note the difficulty of isolating the damage caused by the spill from damage that may be due to other pollutants in the ocean.
Journal reference: PLoS ONE, DOI: 10.1371/journal.pone.0272345
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