NOAA

Dolphins in Barataria Bay off Louisiana, which was hit hard by the BP oil spill in 2010, are seriously ill, and their ailments are probably related to toxic substances in the petroleum, the National Oceanic and Atmospheric Administration suggested on Friday.

As part of a continuing assessment of damages caused by the three-month spill, which began with an explosion aboard the Deepwater Horizon rig in the Gulf of Mexico, NOAA scientists performed comprehensive physicals last summer on 32 dolphins from the bay. They found problems like drastically low weight, low blood sugar and, in some cases, cancer of the liver and lungs.

Yet the most common symptom among the dolphins, found in about half the group, was an abnormally low level of stress hormones like cortisol. Such hormones regulate many functions in the animal, including the immune system and responses to threats. Scientists said the dearth of hormones suggested that the animals were suffering from adrenal insufficiency.



Lori Schwacke, the lead scientist for the health assessment, said the findings were preliminary and could not be conclusively linked to the oil spill at this point. But she said the exams were also conducted on control groups of dolphins living along the Atlantic coast and in other areas that were not affected by the 2010 spill and that those dolphins did not manifest those symptoms.

“The findings we have are also consistent with other studies that have looked at the effects of oil exposure in other mammals,” Dr. Schwacke added, citing experimental studies of mink that were dosed with oil. Some of those minks developed adrenal insufficiency.

Strandings of dolphins began rising in states along the Gulf of Mexico in February 2010, or about two months before the oil spill.

But NOAA says the strandings have returned to normal rates along the Florida coast, which was the farthest from the spill, while remaining abnormally high along the coasts of Louisiana, Mississippi and Alabama. In Barataria Bay alone, with a population of about 1,000 dolphins, 180 strandings have been reported since February 2010. In a normal year, about 20 dolphin standings would be reported in all of Louisiana, the agency said.

Ben Sherman, a NOAA spokesman, cautioned against drawing too broad a conclusion about dolphin deaths across the gulf from the findings. He said the results could provide “possible clues” to the effects of the oil spill on other dolphins in the northern Gulf of Mexico. “However, it is too soon to tell how the Barataria Bay findings apply,” he said.