Unusual String Of Bottlenose Dolphin Deaths Linked To BP Oil Spill

First published on ClimateProgress.org, a project of the Center for American Progress Action Fund, which was recently named one of Time magazine’s Top 25 blogs of 2010.

An “unusual mortality event” among marine mammals — primarily bottlenose dolphins — in the northern Gulf of Mexico has been linked to BP’s historic 2010 oil spill in the Gulf of Mexico.

In research published Wednesday in the journal PloS One, a team of marine scientists from across the country documented a large cluster of dolphin strandings and deaths in the Gulf of Mexico between 2010 and June 2013. Of those strandings and deaths, they said, most occurred in areas impacted by the 2010 BP Deepwater Horizon oil spill.

“[T]he location, timing, and magnitude of dolphin stranding trends observed following the [BP] oil spill, particularly statewide for Louisiana, Mississippi, and Alabama, overlap with the location and magnitude of oil during and the year following [the] spill,” the research reads. “In comparison, the [Gulf of Mexico] coasts of Florida and Texas experienced little to no oiling, and … these areas lacked significant annual, statewide increases in stranded dolphins.”

The peer-reviewed research is just the latest linking the Deepwater Horizon spill to extreme health problems in dolphins, particularly in Louisiana’s Barataria Bay. In a previous study published in 2013, scientists have said that the 4.2 million barrels of oil sloshed into the Gulf of Mexico may be linked to deteriorating dolphin health including missing teeth, lung disease, and hormonal imbalances. That study was funded by BP.

“I’ve never seen such a high prevalence of very sick animals,” said National Oceanic and Atmospheric Administration researcher Lori Schwacke, the lead author of the 2013 study.

BP has vehemently denied that the oil spill was the direct cause of any adverse impacts to dolphin health. Indeed, neither of the studies imply direct causation — they merely note an overlap in the time of the spill and the discovery of sick or dead animals. BP has also noted that prior to the spill, there had been little to no studies of dolphin health, making it difficult to discern whether those problems were ongoing. Health assessments of the Gulf have shown other conditions unrelated to the oil spill that are detrimental to marine mammal health, including other types of pollution and cold temperatures. Because of that variability, the oil giant has made the case that the spill “didn’t ruin the Gulf.”

“It’s important to note that unfortunately these large die-offs of dolphins aren’t unusual,” the company said in a statement to the Times-Picayune. “The study states that there were ten [unusual mortality events] involving bottlenose dolphins documented in the Gulf prior to 2010. Over the past years there have been dolphin UMEs relating to dolphins all over the world, with no connection to oil spills.”

Wednesday’s research also acknowledges that the BP oil spill was not the initial cause of the unusual mortality event, noting that the blowout happened approximately 3 months after scientists had already declared that an unusual mortality event among bottleneck dolphins was occurring in the immediate area. But it speculates that the spill may have have worsened the situation. It says that “large increases in mortalities of birds, turtles, and mammals” were documented in the days and months following the oil release, and pointed out that the longest cluster of dolphin deaths occurred in Louisiana’s Barataria Bay between August 2010 and December 2011, where oil from the spill was present.

“Combined exposures of pregnant females to unusually cold temperatures, freshwater runoff, and DWH oil have been proposed as the cause of the higher numbers of perinate strandings during 2011,” the study reads.

The court case over how much money BP should be liable for the 2010 spill — the largest in U.S. history — is ongoing. Just last month, a Louisiana federal judge ruled that BP should only be held responsible for spilling 3.19 million barrels of oil into the Gulf, which is about a million barrels fewer than the U.S. government’s 4.2 million barrel estimate. Because of that ruling, BP’s maximum fine of $18 billion was decreased to $13.7 billion.

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