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Researchers
investigated the deaths of perinatal dolphins, like this one, found in
regions affected by the 2010 Deepwater Horizon oil spill.© Louisiana Department of Wildlife and Fisheries
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April 12, 2016 - GULF OF MEXICO - Scientists have finalized a four-year study of newborn and fetal
dolphins found stranded on beaches in the northern Gulf of Mexico
between 2010 and 2013. Their study, reported in the journal
Diseases of Aquatic Organisms,
identified substantial differences between fetal and newborn dolphins
found stranded inside and outside the areas affected by the 2010
Deepwater Horizon oil spill.
The study team evaluated 69 perinatal common bottlenose
dolphins
in Alabama, Louisiana and Mississippi, the areas most affected by the
spill, and 26 others found in areas unaffected by the spill. The work
was conducted as part of an effort to investigate an "unusual mortality
event" in the Gulf primarily involving bottlenose dolphins, beginning in
early 2010 and continuing into 2014.
Scientists saw higher numbers of stranded perinatal dolphins in
the spill zone in 2011 than in other years, particularly in Mississippi
and Alabama, the researchers report. The young dolphins, which
died in the womb or shortly after birth, "were significantly smaller
than those that stranded during previous years and in other geographic
locations," they wrote.
Bottlenose dolphin gestation takes about 380 days, so
perinatal
dolphins that died in the early months of 2011 could have been exposed
in the womb to petroleum products released the previous year,
said University of Illinois veterinary diagnostic laboratory professor
Kathleen Colegrove, who led the study. Colegrove works in the
Chicago-based Zoological Pathology Program at the U. of I.
"Dolphin dams losing fetuses in 2011 would have been in the earlier stages of pregnancy in 2010 during the oil spill," she said.
The researchers report that
88 percent of the perinatal dolphins
found in the spill zone had lung abnormalities, including partially or
completely collapsed lungs. That and their small size suggest
that they died in the womb or very soon after birth—before their lungs
had a chance to fully inflate.
Only 15 percent of those found in areas unaffected by the spill had this lung abnormality, the researchers said.
The team also found that the spill-zone dolphins were
"particularly
susceptible to late-term pregnancy failures, signs of fetal distress
and development of in utero infections including brucellosis," a
bacterial infection that can affect the brain, lungs, bones and
reproductive function. Extensive testing found no evidence that an
unusual or highly pathogenic Brucella strain was involved.
"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 said.
A previous study by many of the same researchers revealed that nonperinatal
bottlenose dolphins stranded
in the spill zone after the spill were much more likely than other
stranded dolphins to have severe lung and adrenal gland damage
"consistent with petroleum product exposure."
"These diseases in pregnant dolphins likely led to reproductive losses," Colegrove said.
"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 on the study.
More information: KM Colegrove et al. Fetal distress and in utero
pneumonia in perinatal dolphins during the Northern Gulf of Mexico
unusual mortality event, Diseases of Aquatic Organisms (2016). DOI: 10.3354/dao02969
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PHYS.
