Dolphins living in one of the areas most severely impacted by the 2010 BP oil spill suffer from lung problems consistent with oil exposure, according to the Natural Resource Damage Assessment (NRDA). In 2011, researchers for the NRDA discovered that 48 percent of bottlenose dolphins in Barataria Bay, Louisiana had a “guarded or worse” prognosis, and 17 percent had a “poor or grave” prognosis, meaning they were not expected to survive.

Researchers conducted health assessments of dolphins in Barataria Bay – an area with “heavy and prolonged oiling” – a year after the BP oil spill and examined another group of dolphins in Sarasota Bay, Florida, where oil was not observed, to compare results.

According to the study, which was published in the journal Environmental Science & Technology, Barataria Bay dolphins were 5 times more likely to have moderate to severe lung disease, characterized by symptoms such as lung masses. Researchers also found that 25 percent of dolphins were significantly underweight.

Disease conditions in Barataria Bay dolphins were significantly greater in prevalence and severity than those in Sarasota Bay dolphins, as well as those previously reported in other wild dolphin populations. Many disease conditions observed in Barataria Bay dolphins are uncommon but consistent with petroleum hydrocarbon exposure and toxicity. In the months following the DWH [Deepwater Horizon] spill, dolphins were observed in oiled waters, including BSE [bay, sound, and estuary] waters, at times swimming through surface oil and with oil adhering to their skin. Dolphins therefore had potential for exposure to oil through direct contact at the surface and in the water column, through incidental ingestion from water or sediments while feeding, and through ingestion of contaminated prey.

The dolphins exhibited lung damage and adrenal hormone abnormalities not seen before in other dolphin populations. “I’ve never seen such a high prevalence of very sick animals – and with unusual conditions such as adrenal hormone abnormalities,” Lori Schwacke, lead author of the study, said in a NOAA press release.

Early Wednesday, a BP spokesman disputed the results of the study, and claimed that BP has “repeatedly requested access to the dolphin health data,” the Times-Picayune reports. However, NOAA scientists said that BP officials were provided with data from the study at a press conference on Wednesday afternoon, and were even present during the testing of dolphins in Barataria Bay in 2011. BP has also been paying for the NRDA research.

In August, a study by the non-profit whale research organization, Ocean Alliance, determined that the sperm whale population in the Gulf of Mexico “may be the most polluted in the world” due to the BP oil spill.

Iain Kerr, CEO of Ocean Alliance, said that cell samples taken from sperm whales in the Gulf of Mexico have higher concentrations of metals and elements found in crude oil than any other sperm whale population in the world.

Because whales and dolphins are at the top of the food chain, their health can tell researchers a lot about the health of the Gulf ecosystem as a whole. Toxins absorbed by animals from the bottom of the food chain up would eventually be present in larger predators’ bodies. Whales and dolphins are therefore good bioindicators of the entire ecosystem and, in this case, good indicators of the effects of the oil spill.

In a statement issued early Wednesday, BP spokesman Jason Ryan said the symptoms identified in the dolphin study “have been seen in other dolphin events that have been related to contaminants and conditions found in the northern Gulf,” and said the symptoms are consistent with those observed in dolphins suffering from morbillivirus and brucellosis.

During the Wednesday press conference, Dr. Teresa Rowles, a co-author of the study and leader of the NOAA Marine Mammal Health and Stranding Response Program, said that researchers have already ruled out morbillivirus and “have no evidence at this time that brucellosis is the overarching cause of the unusual mortality event in the northern Gulf.”

Image via: Environmental Science & Technology

Alisha is a writer and researcher with Ring of Fire. You can follow her on Twitter @childoftheearth.