On April 20, 2010, a Deepwater Horizon oil well drilling platform spilled millions of gallons of oil into the Gulf of Mexico following an explosion. According to the National Oceanic and Atmospheric Administration (NOAA), the event became the largest marine oil spill in United States history, with oil reaching the coastlines of Louisiana, Mississippi, and Alabama.
In the succeeding years, an unusual mortality event for cetaceans occurred in the region. As of April 3, 2016, there were 1,591 reported stranding events in the northern Gulf of Mexico.
New research published in Diseases of Aquatic Organisms has focused on newborn and fetal bottlenose dolphins found stranded on beaches in the northern Gulf of Mexico. And the researchers have found what they consider substantial differences between the baby dolphins stranded within the oil spill region and outside the oil spill region.
In their study, the researchers compared 69 perinatal common bottlenose dolphins—found in the oil spill region—with 26 others, which were found stranded in South Carolina and Florida.
From January 2010 through December 2013, 769 dolphin strandings were reported with total body lengths recorded. One-hundred seventy-one, or 22 percent, had a body length under 115 centimeters, considered perinatal.
“There was also a significant increase in the number and prevalence of stranded perinates in Mississippi and Alabama during 2011, and these perinates were significantly smaller than those stranded during previous years in other geographic locations,” the researchers wrote. “The stranding of shorter perinates may indicate that more pre-term dolphins died in utero and were aborted during 2011 in Mississippi and Alabama.”
“Dolphin dams losing fetuses in 2011 would have been in the earlier stages of pregnancy in 2010 during the oil spill,” said study author Kathleen Colegrove, who is a veterinary diagnostic laboratory professor at the University of Illinois, in a statement.
Dolphin gestation usually takes around 380 days.
The researchers found that 88 percent of the perinatal dolphins found in spill regions had lung abnormalities, including partially or completely collapsed lungs. Only 15 percent of perinatal dolphins found outside the spill zone had such lung abnormalities. The former were also more susceptible to brucellosis, an infection that affects the brain, lungs, bones, and reproductive function, with 61 percent compared to 24 percent (for dolphins outside the spill region).
“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,” said NOAA veterinarian Teri Rowles, in a statement.
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