An unusually high number of newborn and fetal dolphin deaths in the Gulf of Mexico between 2010 and 2014 were likely linked to health problems caused by oil exposure from the Deepwater Horizon oil spill, according to a new research study.
The study, published yesterday in the journal Diseases of Aquatic Organisms, found that pregnant bottlenose dolphins were particularly susceptible to late-pregnancy failures and infection. In addition, the dead newborn and stillborn dolphins that were examined also had high rates of infection, in particular with pneumonia, as well as higher than normal rates of lung abnormalities.
The study is the latest addition to a growing body of evidence that the dolphin die-off between 2010 and 2014 was associated with the massive oil spill. Last year, researchers with the National Oceanic and Atmospheric Administration reported that lesions found on the lungs and adrenal glands of dolphins that died in the Gulf of Mexico were an indication of oil exposure. Similar to the perinatal dolphins examined in the most recent study, many of those dolphins too, likely died from bacterial pneumonia infections.
“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,” Teri Rowles, a veterinarian with the National Oceanic and Atmospheric Administration’s Marine Mammal Health and Stranding Response Program and a co-author on the study, said in a statement.
“These findings support that pregnant dolphins experienced significant health abnormalities that contributed to increased fetal deaths or deaths of dolphin neonates shortly after birth,” Kathleen Colegrove, a University of Illinois veterinary diagnostic laboratory professor who led the study, said in the statement.
Researchers from NOAA, the University of Illinois, the National Marine Fisheries Service and elsewhere evaluated tissue from 69 perinatal dolphins that died in the Gulf of Mexico off the coasts of Alabama, Louisiana and Mississippi — areas affected by the oil spill — and compared them to 26 perinatal dolphins found in areas not affected by the spill.
Of the dolphins from the spill sites that died in the womb or shortly after being born, 88 percent were found to have collapsed lungs, 87 percent had “fetal distress” and 65 percent had bacterial pneumonia. For perinatal dolphins from areas unaffected by the oil spill, those numbers dropped dramatically, to 15 percent, 27 percent and 19 percent, respectively.
Dolphins are not the only marine animals to bear the effects of the oil spill. Last year, the National Wildlife Federation published a report that found that between 27,000 and 65,000 Kemp’s ridley sea turtles died during 2010. Other findings included abnormal development in many fish species due to oil exposure, and oil damage to coral reefs.