The Deepwater Horizon oil spill continues to cause problems for wildlife in the Gulf, and a new study finds yet another example. Researchers from the National Oceanic and Atmospheric Administration (NOAA) found that the Barataria Bay population of bottlenose dolphins have an extremely low rate of successful pregnancies.
The spill itself triggered a massive die-off of whales and dolphins, but ongoing effects are still hurting populations. Scientists began monitoring the health of the Barataria Bay population of dolphins following their exposure in 2011, as part of the Natural Resource Damage Assessment for the Deepwater Horizon oil spill. At the time, researchers found that this group of dolphins suffered from a higher prevalence of adrenal dysfunction and lung disease.
The most recent study, published in the Proceedings of the Royal Society this week, not only found a high rate of reproductive failure, but also an increase in overall mortality in the years following the spill.
The NOAA researchers found that only 20 percent of pregnant dolphins in the Barataria Bay population were able to successfully give birth to living calves. That compares with a pregnancy success rate of 83 percent observed in a similar population of dolphins living in Sarasota Bay, which was not directly affected by the spill.
Barataria Bay dolphins also have a lower survival rate compared to the Sarasota Bay dolphins. Dolphins exposed to the oil spill survived at a rate of 86.8 percent per year, compared to 95 percent of unexposed dolphins.
“This evidence suggests that dolphin reproduction and survival is being impacted by chronic disease, indicating that the effects of the [Deepwater Horizon] oil spill have been long-lasting,” the authors conclude. It’s unclear how long it will take the population to recover fully.