Baby Dolphin Deaths Linked To Deepwater Horizon Oil Spills

The high mortality rate among several stillborn and juvenile dolphins in the Gulf of Mexico, from 2010 and 2014, was due to chronic illnesses in mothers impacted by oil spills from the Deepwater Horizon spill.

Experts from the University of Illinois at Urbana-Champaign in a four-year study looked at the death of 69 perinatal common bottlenose dolphins in regions that were most affected by the spill, including Alabama, Louisiana and Mississippi, apart from the death of 26 in areas outside the spill zone.

There were substantial differences between fetal and newborn dolphins on the beaches inside as well as outside the area. Many more perinatal dolphins were found in the spill zone in 2011 than at any other spot. Dolphins that died in the womb or just after birth, were smaller than others stranded in previous years or in regions outside the spill zone.

With the gestation period for bottlenose dolphins being 380 days, perinatal dolphins stranded in the early months of 2011 might have got affected by petroleum products released in the earlier years, when they were still their mothers' wombs.

"Dolphin dams losing fetuses in 2011 would have been in the earlier stages of pregnancy in 2010 during the oil spill," explained  Kathleen Colegrove, a University of Illinois veterinary diagnostic laboratory professor, who led the study.

About 88 % of the dolphins showed lung abnormalities, including partially or completely collapsed lungs. Their unusually small body sizes also indicate that they died in the womb or soon after they were born, before their lungs could develop.

Late-term pregnancy failures, such as fetal distress and in-utero infections included bacterial infections affecting the brain, lungs, bones and reproductive function were also detected.

"These findings support that pregnant dolphins experienced significant health abnormalities that contributed to increased fetal deaths or deaths of dolphin neonates shortly after birth," Colegrove added. "These diseases in pregnant dolphins likely led to reproductive losses."

"Our new findings add to the mounting evidence from peer-reviewed studies that exposure to petroleum compounds following the Deepwater Horizon oil spill negatively impacted the reproductive health of dolphin populations living in the oil spill footprint in the northern Gulf of Mexico," said Dr. Teri Rowles, a veterinarian with the National Oceanic and Atmospheric Administration's Marine Mammal Health and Stranding Response Program and a co-author.

Their findings were recently published in the journal Diseases of Aquatic Organisms.