A new study has found that dolphins in the Louisiana bay, which was polluted by BP's offshore oil spill in 2010, have a harder time reproducing, according to CBC News. Researchers tracked 10 pregnant dolphins over the course of four years and found that only two of them ended up successfully giving birth.

"The take-home message is that this dolphin population, as well as other dolphin and whale populations that were exposed to the Deepwater Horizon oil, will take a long time to recover," said Lori Schwacke, lead researcher of the study.

Hundreds of dead dolphins have continued to wash ashore since the spill, and the new research shows that the ones that have survived may be suffering from damage to their reproductive systems, according to Mongabay. Furthermore, the researchers observed a unique behavior among the female dolphins whereby they push their dead babies through the bay waters.

"You have to connect the dots, and the dots have not been connected," said Moby Solangi, the head of the Institute for Marine Mammal Studies in Gulfport, Miss. "We have to look at the overall ecosystem to see how these animals will recover."

In addition to reproductive damage, many dolphins suffer from skin lesions as a result of the spill, The Pensacola News Journal reported.

The study was published in the Nov. 4 issue of the Proceedings of the Royal Society B.