Bottlenose Dolphins Oiled By Deepwater Horizon Spill are Sick and Dying

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The dolphins in the Gulf of Mexico are sick and dying, Captain Lori DeAngelis—who is more commonly known as the Dolphin Queen by the folks in Orange Beach, Alabama—told me last Christmas.  She was right.  Today, we finally have more scientific evidence as to why.

A study published yesterday in the journal Environmental Science & Technology compared bottlenose dolphins in Barataria Bay, Louisiana that were oiled by the Deepwater Horizon spill with ones in Sarasota Bay, Florida that did not come into direct contact with the oil spill and found that the Louisiana dolphins were sicker.  Much sicker.

Dolphins swimming in emulsified oil off the coast of Louisiana during the Deepwater Horizon oil spill. Credit: NRDC.

The study is the first to confirm that bottlenose dolphins in the areas heavily affected by the Deepwater Horizon oil spill are suffering injuries that are consistent with exposure to petroleum hydrocarbons.  The answer to the Dolphin Queen’s mystery of why the dolphins are dying is in the oil.  But, she knew that.


Captain Lori DeAngelis, aka “The Dolphin Queen” on her boat in Orange Beach, AL Credit: Rocky Kistner.

Ever since the Deepwater Horizon catastrophe, something has been terribly wrong with the dolphins, the Dolphin Queen warned me.  I was on a kayaking trip with a friend in the Gulf of Mexico when we got caught in a hurricane.  The Dolphin Queen invited us to wait out the storm at her house, where we ate Christmas ham with her family and listened as she talked about her favorite subject: the dolphins. 

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Kayaking in the Gulf of Mexico, December 2012.  Credit: Daniel Alvarez.

For Captain Lori, the local pods are kin.  She knows them, has a special noise she calls them with (sounds a bit like "wooo wooo"), can identify individuals by their fins, can tell you where certain pods like to hang, and doesn’t need a scientific study to know when they aren't feeling well.  

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Young adult male dolphin in Orange Beach, AL.  Credit: Jerry Cope.

Yesterday’s study was conducted as part of the Natural Resources Damage Assessment (NRDA) by a team of researchers that included government, academic, and non-governmental scientists.  The scientists found that the Barataria Bay, Louisiana dolphins—the ones that had been directly exposed to the oil spill—were ill with a variety of heartbreaking symptoms. Nearly half of the Louisiana dolphins sampled were given a “guarded or worse” prognosis, and seventeen percent were expected to die. 

Dolphins swimming in oil and chemical dispersants near Breton National Wildlife Refuge off the Mississippi coast, not far from Barataria Bay, Louisiana. Credit: NRDC.

Twenty-five percent of the Barataria Bay, Louisiana dolphins were underweight, and they were five times more likely to have moderate to severe lung disease compared to the Sarasota Bay, Florida dolphins.  Lung disease in humans and other animals, the study explains, has been linked to ingestion of petroleum hydrocarbons. 

Three of the Louisiana dolphins had no teeth or almost no teeth and three more had extensive tooth loss.  None of the Florida dolphins had tooth loss, and a healthy bottlenose dolphin normally has between 76 and 108 teeth.

One Louisiana bottlenose dolphin—that had lung disease and was in poor condition generally—was five-months pregnant.  When the scientists conducted an ultrasound, there was no heartbeat or movement: it was, in their words, a nonviable fetus

The Louisiana dolphins had clinicopathologic abnormalities—e.g., inflammation, hypoglycemia, altered iron metabolism, and hepatobiliary disease.  Almost none of the Florida dolphins had any of these abnormalities.  The Louisiana dolphins also had low concentrations of adrenal hormones.  Adrenal hormones are our “fight or flight” hormones; they kick in during stressful situations.  In humans, extreme or chronic prolonged stress has been linked to adrenal dysfunction, and the scientists explain, if left untreated in humans low adrenal levels (i.e. hypoadrenocorticism) can be life threatening, especially in times of stress or pregnancy.

“[T]he severity of disease, poor body condition, and high prevalence of abnormalities seen in the [Barataria Bay, Louisiana] dolphins is in stark contrast with the overall health status from the . . . reference site, as well as with health conditions previously documented in bottlenose dolphins from other U.S. coastal sites,” the scientists grimly conclude.

This is tragic news for the bottlenose dolphins of the Gulf, who have been dying in droves.  The dolphins in the northern Gulf of Mexico are undergoing what is referred to as an Unusual Mortality Event (UME)Over a thousand dolphins in the northern Gulf of Mexico have died in this series of mass mortality events.  There have been other UMEs in the Gulf of Mexico, but never have the dolphins experienced a die-off that lasted as long and involved as many animals or calves.


National Oceanic and Atmospheric Administration (NOAA) map of the stranding locations from the 2010-2013 Unusual Mortality Event in the Northern Gulf of Mexico.  Bottlenose dolphin strandings are represented by green circle symbols. 

The die-off is especially devastating because, as the Dolphin Queen will tell you, the Gulf’s bottlenose dolphins do not belong to a single group.  Marine scientists divide them into offshore, continental shelf, coastal, and estuary, bay, and sound populations, which do not mate with one another and are genetically distinct.  The near-coastal population breaks down further into semi-isolated communities, some with fewer than 100 animals, and these communities are probably being decimated.  


Kayaking near Orange Beach, Alabama, December 2012.  Credit: Daniel Alvarez.

Because these intimate coastal communities are often so small, the Dolphin Queen can greet her local dolphins like family. 

But, the dolphins in Barataria Bay, Louisiana  are telling us something.  Their message is in their skinny bodies, toothless mouths, diseased lungs, stressed glands, and dead calves.  They are telling us that dolphins cannot swim, breed, eat, and survive with oil.  They are telling us that the Deepwater Horizon catastrophe is far from over.