Scientists at the University of Illinois at Urbana-Champaign have linked an "unusual mortality event" involving bottlenose dolphins along the coast of Louisiana, Mississippi, and Alabama to the 2010 Deepwater Horizon oil spill. In a recent study published in Diseases of Aquatic Organisms, the researchers determined that fetal and newborn dolphins in the spill area were more likely to have died in utero or shortly after birth than dolphins outside the area.

From February 2010 to December 2013, the scientists evaluated 69 perinatal dolphins found stranded in areas heavily affected by the spill and compared them to 26 bottlenose dolphins unaffected by the spill, Motherboard reports. The dolphins stranded in the spill zone were much smaller than those outside of it, suggesting they were preterm fetuses or "very young newborns," the study says.

The study found that 88 percent of dolphins tested within the spill zone had some kind of lung abnormality, 87 percent showed signs of fetal distress, and 60 percent were exposed to in utero infection. The scientists also looked for other characteristics that might be indicative of oil exposure, such as fetal folds, creased dorsal fins, rostral hairs (near the mouth), and dental eruption.

The findings corroborate a similar study by the National Oceanic and Atmospheric Administration released last year. That study found that dolphins in the Gulf of Mexico between 2010 and 2012 exhibited high numbers of pneumonia, adrenal issues, and lung disease. The researchers at the University of Illinois wanted to better understand the longterm effects of the oil spill on bottlenose dolphin populations in the Gulf area. The study says more research will need to be done to determine if the oil spill had an effect on the reproductive success of the dolphins in the area.