Dolphins swimming through oil on the surface of the Gulf of Mexico, during the 2010 Deepwater Horizon oil spill. Source: NOAA
Bottlenose dolphin in the northern Gulf of Mexico are exhibiting signs of severe health issues according to the preliminary results of physical examinations given to 32 live dolphins last summer.
The examinations were conducted in Louisiana’s Barataria Bay, one of the areas most heavily impacted by the Deepwater Horizon oil spill a year earlier, during which nearly 5 million barrels of crude were estimated to have leaked into the Gulf over the course of 3 months.
According to marine mammal biologists, “many of the dolphins in the study are underweight, anemic, have low blood sugar and/or some symptoms of liver and lung disease. Nearly half also have abnormally low levels of the hormones that help with stress response, metabolism and immune function.”
Although preliminary, the results are being shared now in an effort to help rescuers and veterinarians can better care for live, stranded dolphins and to be on the lookout for similar health conditions.
Since February 2010 — 2 months prior to the April 20 explosion that caused the worst offshore oil spill in U.S. history — more than 675 dolphins have stranded in the northern Gulf of Mexico (from Franklin County, Florida, to the Louisiana/Texas border) – much higher than the average rate of 74 dolphins per year, prompting NOAA to declare an Unusual Mortality Event (UME) and investigate the cause of death for as many of the dolphins as possible.
The overwhelming majority of dolphins stranded in the region have been found dead. Of the 33 that were stranded alive, 7 have been taken to facilities for rehabilitation.
Potentially more toxic to marine life than oil from the ruptured well was the unprecedented, deepwater use of 1.1 million US gallons (4,200 m3) of chemical dispersants, sprayed into the water at the site of the leak in order to disperse the oil before it could reach the surface.
Along with its local, state and federal partners, NOAA is researching the mechanisms by which Gulf dolphins may have been exposed to oil and toxic chemicals, whether through ingestion, inhalation or externally.
Dolphins may have routinely ingested oil from sediments or water while feeding or by eating whole fish, including internal organs and fluids such as liver and bile, which can harbor chemical contaminants.
