Exposure to Deepwater Horizon oil caused illnesses that resulted in the early deaths of baby dolphins from 2010 into 2014 and possibly beyond, a new study finds.
Published in the journal Diseases of Aquatic Organisms, the study is a continuation of a number of research projects into the high number of dolphin deaths along the northern Gulf of Mexico in the wake of the 2010 oil spill. In this newest study, the researchers found that 88 percent of the stillborn and dead young dolphins found in areas impacted by the oil had abnormal lungs compared to 15 percent of young dolphins found in other areas.
The collapsed lungs of these young dolphins show they either died in the womb or shortly after being born, according to the report by the National Oceanic and Atmospheric Administration and a number of research partners.
The latest report builds on a body of research that has gone on since the 2010 oil Deepwater Horizon disaster.
A 2015 study showed stranded dolphins in the oiled area had a much greater chance of lung and adrenal gland damage than other dolphins. A 2013 study found dolphins in Barataria Bay, one of the more heavily oiled areas in Louisiana, were seriously ill. Almost half of the 32 dolphins sampled in that study were found to be in bad health, with almost 17 percent not expected to live much longer.
In the most recent study, researchers determined that the highest number of the dead, young dolphins were found in 2011, a year after the oil spill. Because bottlenose dolphins carry their young for an average 380 days, the young dolphins could have been exposed to oil during the previous year while in the womb. Although 2011 was the peak, the higher than normal death rates of young dolphins continued after that, said Jenny Litz, biologist with NOAA’s Marine Mammal Program.
“Reproductive success has been damaged, and it’s not clear how long those effects will go on,” Litz said. “It’s how long it will last that’s in question.”
A study on live dolphins in Barataria Bay released in November, showed that dolphins were having problems having calves. The study found about 20 percent of the dolphins sampled produced a viable calf compared to an 83 percent success rate reported previously in areas without oil damage.
Stephanie Venn-Watson, director of the Translational Medicine and Research Program with the National Marine Mammal Foundation, said the type of adrenal gland disease found in the adult dolphins fits with the number of young dolphins they found dead.
“Animals that have this type of adrenal disease run the risk of late term pregnancy problems,” Venn-Watson said. “It begs the question of other long-term impacts on other species.”
Litz said the studies focused on dolphins living near shore or in estuaries and it’s likely offshore dolphins experienced similar problems.
“It will be important to monitor these populations long term,” Litz said.
All the researchers agreed that it’s likely that other marine animals have had similar problems.
“It’s a species (dolphins) we can most easily study,” Kathleen Colegrove, the study’s lead author and veterinary pathology professor at the University of Illinois Chicago-based Zoological Pathology Program. “What we may be looking at is the tip of the iceberg.”
It’s too early to say how the dolphin deaths and problems reproducing will have on the long-term population of the animal, but researchers said they will continue monitoring.
“Dolphins are a long-lived species, so it could be years before we know the full impact,” Colegrove said.
An Unusual Mortality Event of dolphins in the northern Gulf of Mexico has been running since 2010, although there are investigations on whether it’s time to close that, Litz said.
The peak mortality was between 2010 and 2014; however there was a more recent uptick in deaths along the coast of Mississippi and the panhandle of Florida.
There was a red tide in the area during that time, so researchers are looking into that as well, Litz said.
The study is the result of teamwork of researchers from the University of Illinois, National Marine Mammal Foundation, NOAA, the Dauphin Island Sea Lab and University of South Alabama, the Institute for Marine Mammal Studies in Mississippi, the Louisiana Department of Wildlife and Fisheries, Animal Health Center in British Columbia, the Mote Marine Laboratory in Florida, the University of Georgia and the University of North Carolina.
Follow Amy Wold on Twitter, @awold10.