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Oil Pollution is Making Gulf Dolphins Sick

The views expressed are those of the author and are not necessarily those of Scientific American.


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For eighty-seven days in 2010, 210 million gallons of oil from wells below the Deepwater Horizon poured into the Gulf of Mexico. Researchers announced recently that as a result, Bottlenose dolphins in Louisiana’s Barataria Bay are suffering from a host of maladies, including lung disease and adrenal problems. They’re also losing their teeth. The research was conducted in August 2011, by a team of governmental, academic, and non-governmental scientists as part of the post-spill Natural Resource Damage Assessment.

To understand what the effects of oil contamination were on marine mammals like dolphins and whales, the team conducted health assessments on thirty-two Barataria Bay dolphins in 2011, a site chosen because that area was heavily oiled during and after the spill. The team compared those dolphins to twenty-seven from Sarasota Bay, Florida, where researchers were already conducting a decades-long study of dolphin health, and which was lucky enough to remain oil-free following the blowout.

The team sampled each dolphin’s blubber, collected blood and urine samples, conducted ultrasounds, took body-size measurements, and more. The results were published in December in the journal Environmental Science and Technology.

I have an article in today’s edition of the Washington Post Health and Science section describing the findings of the assessment. Here are some highlights:

“There’s disease in any wild population,” said lead researcher Lori H. Schwacke, branch chief of the National Oceanic and Atmospheric Administration’s Centers for Coastal Ocean Science. “But we just haven’t seen animals that were in such bad shape as what we saw in Barataria Bay.”

Veterinarians collect a urine sample from a 16-year old adult male bottlenose dolphin caught near Grand Isle, Louisiana. His evaluation determined he was significantly underweight, anemic, and had indications of liver and lung disease. Radio and satellite linked tags were attached before he was released.

The researchers were particularly surprised to find that the Barataria Bay dolphins had unusually low levels of the adrenal hormones cortisol and aldosterone, compared with the Sarasota dolphins. When faced with a stressful situation, the adrenal glands typically pump out hormones, which in turn increase heart rate and blood sugar, preparing the animal for a fight-or-flight response. That response allows the dolphins to respond appropriately to stressful or threatening situations, such as being attacked by a predator.

About 25 percent of the Barataria Bay dolphins were also found to be significantly underweight in comparison with just one of the Sarasota Bay dolphins. Many had low blood sugar, and several had low red blood cell counts. For six of the Barataria Bay dolphins — but none of those from Sarasota Bay — blood tests revealed liver abnormalities.

“Some of the animals’ lung disease [was] so severe that we did consider those conditions life-threatening,” said researcher Cynthia R. Smith, executive director and director of medicine for the National Marine Mammal Foundation. At least one of the dolphins that the team examined died about five months later; a necropsy resulted in the relatively rare diagnosis of bacterial pneumonia.

It’s worth pointing out that the cetacean populations in the northern Gulf of Mexico are stranding in record numbers, something that NOAA refers to as an “unusual mortality event,” or UME. What’s interesting is that the UME began several months before the Deepwater Horizon blowout.

What the research makes clear, especially by comparing the Barataria Bay dolphins to those from Sarasota, is that the oil contamination is seriously affecting the health of marine mammals (and other marine life as well). But some parts of the Gulf, including Louisiana’s Barataria Bay, were already bad news for dolphins and other animals. The oil is but one from an array of environmental stressors and pollutants, which also includes shipping noises, toxic algal blooms, other types of industrial runoff, and more.

Head on over to the Washington Post to read the entire thing.

Researchers measure a dolphin's tail in Barataria Bay.

Researchers measure a dolphin's dorsal fin in Barataria Bay.

Schwacke L.H., Smith C.R., Townsend F.I., Wells R.S., Hart L.B., Balmer B.C., Collier T.K., De Guise S., Fry M.M. & Guillette L.J. & (2013). Health of Common Bottlenose Dolphins (Tursiops truncatus) in Barataria Bay, Louisiana, Following the Deepwater Horizon Oil Spill, Environmental Science & Technology, 131218010126007. DOI:

All images via NOAA/Fisheries, used with permission.

Jason G. Goldman About the Author: Dr. Jason G. Goldman received his Ph.D. in Developmental Psychology at the University of Southern California, where he studied the evolutionary and developmental origins of the mind in humans and non-human animals. Jason is also an editor at ScienceSeeker and Editor of Open Lab 2010. He lives in Los Angeles, CA. Follow on . Follow on Twitter @jgold85.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. tuned 10:48 am 03/5/2014

    Fossil Fuel Monsters couldn’t care less if everything dies off except themselves.

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  2. 2. aliceparker 12:19 am 03/7/2014

    Great reporting, Jason. Sad for the dolphins. Reminds me of the studies my uncle did after the Exxon Valdez. Have we learned nothing??

    Link to this
  3. 3. ramfroggie 1:40 pm 03/10/2014

    Horrendous. Just horrendous and heartbreaking. There is no excuse for this and I am so done hearing about how it’s recovered and how things are back to normal. No, they aren’t, and they won’t be. SHAME.

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  4. 4. 14353262 11:03 am 05/6/2014

    it is good to see that scientist are taking an interest in the well being of bottle nose dolphins. the oil spills in the gulf of mexico had a tremendous negative impact on these beautiful creatures. much is needed to be done to prevent another oil spill so that these dolphins can live in a peaceful environment.

    Link to this

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