Study Links Infant Dolphin Deaths to GoM Spill

In a study released Tuesday, researchers led by Kathleen Colegrove of the University of Illinois at Urbana-Champaign found high levels of in utero mortality from bacterial pneumonia in beached infant dolphins along the Gulf Coast from 2010-2013 – the years following the Deepwater Horizon blowout and spill. 

The authors said that the study builds on earlier research suggesting a connection between the health of local dolphin populations and the Deepwater Horizon incident, and that the previously observed poor health of adult dolphins in the affected region may have resulted in degraded maternal immune systems – potentially leading to an inability to resist infection and the high observed rate of miscarriage and infant mortality.  

"As part of an investigation into the potential impact of the . . . oil spill, health assessments conducted during August 2011 on live [mature] dolphins within the . . . region demonstrated a high prevalence of advanced lung disease . . . poor body condition, and overall guarded to poor prognoses for survival. Corresponding to these changes noted in live dolphins, [mature] dolphins dying in Louisiana, Mississippi, and Alabama from 2010−2012 had an increased prevalence of . . . bacterial pneumonia. Any of these abnormalities could have led to abortion in pregnant dolphins.

“Given that the high prevalence of brucellosis [lung infections] and greatest increases in [fetus] strandings were not apparent until after the oil spill, there may have been oil-associated factors that led to an increase in failed pregnancies, one of which may have included altered maternal immune system function resulting in increases in illnesses."

Previous studies of terrestrial mammals have shown a link between exposure to hydrocarbons and immune system degradation, and studies in human populations have shown a link between exposure to hydrocarbons during pregnancy and an increased risk of miscarriage, the study said. 

However, the authors were careful to note that more study would be needed to establish a causal link between the 2010 spill and the unusual increase of infection-related miscarriages in the local dolphin population from 2010-2013. "Pregnant dolphins from Alabama and Mississippi, especially during 2011, were susceptible to earlier fetal losses than had been reported in previous years and to Brucella-associated abortion . . . [but] there continues to be a need to understand why dolphins were particularly susceptible to late-term fetal loss in this [unusual mortality event], including the potential contributing role of the Deepwater Horizon oil spill."