A study from the National Oceanic and Atmospheric Administration, published last week in the peer-reviewed journal Environmental Science and Technology, produced the strongest evidence to date linking mass dolphin deaths in the Gulf of Mexico to petroleum hydrocarbon exposure and toxicity. The focus of the study, 29 dolphins from Barataria Bay (an area heavily oiled during the BP spill), were found to have lung disease, abnormally low levels of adrenal gland hormones, liver problems and other health effects which are rare but consistent with exposure to oil.
A quarter of the dolphin subjects were found to be significantly underweight, 48 percent were given a guarded prognosis, and 17 percent were in poor or grave condition, meaning they were expected to die soon. The study concludes that the health effects seen in the Barataria Bay dolphins are significant and likely will lead to reduced survival and ability to reproduce.
In an earlier NOAA study in 2011, preliminary research findings indicated oil and Corexit physically stressed Gulf dolphins to death by decreasing their immunity and making them more susceptible to diseases such as brucella and morbillivirus. Morbillivirus was found to be the cause of a majority of dolphin deaths in a recent die off pattern along the Eastern Seaboard throughout the year.
According to a New York Times piece from last Sunday, in the past year at least 1,000 bottlenose dolphin carcasses (eight times the historical average) washed up on beaches in New York, Virginia, the Carolinas, Georgia and Florida. In Florida, 80 dolphins who live permanently in the state’s polluted Indian River Lagoon estuary have died while 233 were reported dead in the northern Gulf of Mexico this year.
While effects of the BP oil spill and corexit haven’t been ruled out as a factor in the East Coast dolphin deaths, research on some of the dead dolphins in the Florida estuary found high levels of mercury, fungal diseases, antibiotic-resistant bacteria, oral-genital tumors and emaciation, most likely a result of environmental pollution.