It's been six years since the Deepwater Horizon oil spill, and scientists are still working to get a fuller picture of how it's affected wildlife. Here's more bad news to add to the pile: the oil spill has been linked to an increase in deaths of newborn and fetal dolphins in affected areas.
A new study, published April 12 in Diseases of Aquatic Organisms, also connected the oil spill to lung problems in juvenile dolphins. It's a reminder of just how disastrous the oil spill has been.
In the study, which ran from 2010 to 2014, US researchers tracked dead fetal and newborn dolphins both inside, and outside, the spill zone. They ended up evaluating 69 common bottlenose dolphins in Louisiana, Alabama and Mississippi—places that got the worst of the spill—and 26 more dolphins found in areas that weren't in the spill zone.
There were more stranded newborn and fetal dolphins found inside the spill zone in 2011 compared to other years, especially in Mississippi and Alabama; and the animals were "significantly smaller" than those in unaffected areas, or those that washed up in the years before the spill, they write.
More disturbing, 88 per cent of the stranded dolphins found in the spill zone had abnormalities in their lungs, including organs that were partially or completely collapsed. Outside the spill zone, just 15 per cent of the animals they found had this type of problem, which could suggest they died before birth, or right after—before their lungs could properly inflate.
"Dolphin dams losing fetuses in 2011 would have been in the earlier stages of pregnancy in 2010 during the oil spill," said lead author Kathleen Colegrove, a professor at the University of Illinois, who adds that the gestation of a bottlenose dolphin takes about 380 days.
This isn't the first study to link reproductive problems in dolphins to the Deepwater Horizon spill. The same team was behind another report linking dolphins' oil exposure to lung damage and other significant problems.
"These dolphins had the most severe lung lesions I have ever seen in dolphins in the US," Colegrove said at the time.
Scientists like to point out that finding a link isn't the same as proving a cause. Still, a growing body of work is starting to outline some disturbing effects suffered in dolphins after the spill.