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Dolphins are dying at an alarming rate along the Gulf Coast. No one knows why.

Why are dolphins dying on the Gulf Coast?
Dolphins are dying at an alarming rate along the Gulf Coast. No one knows why. 02:58

Scientists are puzzled by a disturbing trend in the waters along four Gulf Coast states: almost 300 dead and dying dolphins have washed ashore since February, about three times the usual number.  

From Louisiana to the Florida Panhandle, coastline residents keep seeing a dolphin die-off. They're all bottlenose dolphins, which live closest to shore, and many were adults. The single-day record is nine.

"I would say it's concerning, and bordering on alarming, primarily because it's a group of dolphins that have been impacted because of other unusual mortality events," said Erin Fougeres, who oversees the NOAA's Marine Mammal Stranding Program. Fougeres pointed out that this is the same area that was impacted by the Deepwater Horizon spill, the 2010 explosion on an oil rig that killed 11 people and carried oil hundreds of miles from the well. 

Scientists are exploring several possible causes, from the lingering effects of the oil spill to skin lesions on many recovered dolphins that indicate freshwater exposure. It could also be chemicals, pollutants, or a combination.

"It's an area where dolphins have been previously exposed to oil, they have compromised health. They have lingering health issues and so they are more susceptible to any additional stressor," Fougeres said, adding "anything could tip them potentially over the edge." 

There's a lot of work to do. "Even if the numbers stopped right now, we still have a long way to go, so the work isn't gonna end," she said, adding "We'll be figuring out which tests and which analyses we need to conduct and we're going to move forward with that."

Whatever's happening, there is no known threat to people.

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