British Petroleum-leased oil rig that exploded in 2010 caused deaths and disease in marine life

Dolphins swimming in the oil-contaminated waters of the Gulf of Mexico after the 2010 BP spill suffered unusual lung lesions and died at high rates because of petroleum pollution, according to US scientists.

The report in the peer-reviewed journal PLOS ONE on Wednesday presents the strongest evidence to date the environmental disaster that was unleashed when the BP-leased Deepwater Horizon rig exploded on April 20, 2010, pouring 4.9 million barrels of oil into the sea, was the reason for an unusually high number of dead or dying bottlenose dolphins washing up on the shores of Louisiana, Mississippi and Alabama.

Dolphins take big, deep breaths right at the surface of the water, where oil sheens are most concentrated, and "where there is a good chance of inhaling oil itself", said lead author Stephanie Venn-Watson, a veterinary epidemiologist at the National Marine Mammal Foundation.

"Dolphins were negatively impacted by exposure to petroleum compounds following the Deepwater Horizon oil spill, and exposure to these compounds caused life threatening adrenal and lung disease that has contributed to increased dolphin deaths in the northern Gulf of Mexico," she said.

Unusual lesions in the lungs and adrenal glands, which regulate hormones and stress response, were a key sign that something was wrong with dolphins in the area of the spill, according to the research that compared autopsies of 46 dolphins that were stranded and died in the spill area from June 2010 to August 2012 to a comparison population of stranded dolphins off the Gulf coast of Florida.

"We found that dolphins that died after the oil spill had distinct adrenal gland and lung lesions that were not present in the stranded dolphins from other areas," said Kathleen Colegrove, a veterinary pathologist at the University of Illinois.