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What's killing the Gulf of Mexico's dolphins?
Two years after the BP oil spill, the Gulf is still suffering a historic dolphin die-off. Experts say oil is a likely culprit, but evidence remains elusive.
Thu, Apr 19 2012 at 4:32 PM
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SEA MINUS: Bottlenose dolphins and other marine mammals have been mysteriously dying by the hundreds along the Gulf Coast since early 2010. (Photo: Stephen McCulloch, HBOI/NOAA)
In just two years, more than 600 bottlenose dolphins have washed onto U.S. shores from the Gulf of Mexico, about 95 percent of them already dead. Such "unusual mortality events" have hit Gulf dolphins before, but this one is different. In terms of total deaths, calf deaths and overall duration, it's unprecedented in recorded history.
And it conspicuously parallels another unusual event for the Gulf Coast: the BP Deepwater Horizon oil spill, which also began two years ago.
Scientists still can't definitively link the two disasters, and large numbers of dolphins actually started washing ashore in February 2010, two months before the spill began. But the problem has grown much worse in the two years since, and given its historic severity — especially in Louisiana's Barataria Bay, which was heavily oiled in 2010 — there is concern on the Gulf Coast that oil is at least playing a role.
"The Barataria Bay dolphins have severe health problems that are not showing up in dolphins from the un-oiled area, and have not been seen in previous studies of dolphins from other sites along the Atlantic coast or the Gulf of Mexico," explains a fact sheet from the National Oceanic and Atmospheric Administration, which is studying the die-off. These dolphins "are underweight, have low hormone levels, low blood sugar, and some show signs of liver damage," NOAA reports, adding that their symptoms "are consistent with those seen in other mammals exposed to oil."
Not only do the symptoms raise red flags, but so do the numbers and locations of dying dolphins. From 2002-2009, Louisiana averaged 20 dolphin strandings per year, but then had 139 in 2010, 91 of which occurred after the BP spill began. 2011 was even worse, with 159 strandings statewide — almost eight times the '02-'09 average. Alabama and Mississippi had four and five times the normal stranding rate in 2011, respectively, and 100 cetaceans have already washed up across the Gulf Coast in 2012. Yet strandings are back to normal in Florida, which is farther from the spill site.
"This magnitude of strandings in the northern Gulf is unprecedented," NOAA explains. "Further, there is no evidence that two of the most common causes of previous dolphin die-offs in the Gulf, morbillivirus and marine biotoxins, are the cause of this UME." NOAA does note that 11 stranded dolphins have tested positive for Brucella bacteria, but as veterinary epidemiologist Stephanie Venn-Watson told the New Orleans Times-Picayune last year, that doesn't necessarily rule out oil. "The dolphins may be more susceptible to severe infection because their immune system is not working well," she said, "or the pathogen ... becomes stronger and thus are able to do more damage."
Here's a NOAA bar chart of all marine-mammal strandings along the U.S. Gulf Coast since 2010, compared with the 2002-'09 baseline (note that April 2012 doesn't have a full month's worth of data yet):
And here's a NOAA map of all the 2012 strandings through April 15 (click the image to enlarge, and compare to similar maps for 2011 and 2010):
If these "severely ill" dolphins really were sickened or at least weakened by BP oil, NOAA lists the following ways it could have happened:
- Inhaling vapors at the water's surface.
- Ingesting oil from the sediment or water while feeding.
- Eating whole fish, including internal organs and fluids, such as liver and bile, which can harbor chemical contaminants.
- Absorption through their skin.
There are nine different dolphin species in the Gulf of Mexico, plus Bryde's whales, sperm whales, orcas and several other types of smaller toothed whales. But while many of these cetaceans gravitate toward deep waters, bottlenose dolphins are the only ones found in all Gulf coastal habitats — NOAA estimates their overall population to be around 10,000. A tenth of those are thought to live in Barataria Bay.
Of course, dolphins and whales aren't the only ones affected by the Gulf oil spill. Eleven people lost their lives when the Deepwater Horizon exploded, and countless more have suffered from the spill's ecological and economic effects. More than 200 million gallons of crude flowed into the Gulf between April and July 2010 — followed by thousands of gallons of chemical dispersants — wreaking havoc with a wide range of sea creatures, including plankton, fish, crabs and coral. A three-year, $112 million research project is now examining how much lasting damage this has done.
And, as Al Jazeera English reported this week, Gulf animals are already showing strange deformities — even those that weren't alive in 2010. Young killifish are growing up with misshapen hearts, for example, while shrimp whose grandmothers were exposed to the oil spill are being born without eyes. See the video report below:
The dolphin deaths have proved especially compelling, though, both because dolphins are a sentinel species and because they're smart, charismatic mammals like us. On top of that, their current plight is worse than anything the Gulf has seen in decades — and it might be even worse than we realize. Matthew Huelsenbeck, a marine scientist with Oceana, tells the Sarasota Herald-Tribune that the 600 dolphins stranded since April 2010 may represent just 2 percent of the total number killed.
NOAA plans to issue a final report on the Barataria Bay dolphins within the next six months, but cautions that "results for other areas will take longer, because new samples are still being collected." Meanwhile, if you're on the Gulf Coast and find any oiled, injured or dead marine animals, NOAA asks that you call one of these numbers:
Dolphins and whales
1-877-WHALEHELP (1-877-942-5343)
Manatees
Florida: 1-888-404-FWCC (1-888-404-3922)
Louisiana, Mississippi and Alabama: 1-904-731-3079
Sea turtles
Texas: 1-866-TURTLE5 (1-866-887-8535)
Louisiana: 1-337-962-7092
Mississippi: 1-888-SOS-DOLPHIN (1-888-767-3657)
Alabama: 1-866-SEA-TURT (1-866-732-8878)
Florida: 1-888-404-FWCC (1-888-404-3922)
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I live in the Panhandle of Florida and on the Bay. We used to see dolphins swim by almost daily before the oil spill. Now we see none. That is really scary. It is very very sad for us, because that used to be the highlight of our day to watch them swim by.
The actual count is 47 dolphins dead, The area in question has always been tough on them ,because ,Navy somar.
The actual count is 47 dolphins dead, The area in question has always been tough on them ,because ,Navy somar.
Oil in the gulf, fracking in Pennsylvania polluting ground water. We are destroying ourselves before our very eyes for the almighty oil and gas. This is one sorry state of affairs. No clean water, no safe fish to eat.
Could it be the solar flares? I see the chart does not go back beyond the last solar maximum. It would be nice to see a time frame from 2000 and on.
(So long! And, thanks for the fish!)
You're kidding, right? Of COURSE it was the BP oil spill. We are just now finding out that they lied and covered up the true amount of oil that blasted into the gulf. Those guys should be hung.
It's less the oil, and much more the extremely toxic "Corexit" dispersant chemical. The problem may have disappeared from public view, but the stuff is still down there..... many thousands of feet, in the low spot - it hasn't 'dispersed'. Eventually it may rise like a B-movie monster to invade our beaches again.....
I live on the Gulf Coast near Mobile, ALabama. Tar balls still wash up in Gulf Shores. Many fish caught out in the area affected by the spill in the Gulf have black stripes on them and open sores. Of course it's the oil. There is no other logical reason that dolphins would die and wash up on the beaches that were affected by the disaster. Use some common sense people. Why are we even debating this? BP and its partners on that rig need to be held responsible for this as well.
It's the damn dispersant used to keep it out of sight , but not in reality, disapear. Much worse than the oil itself. Yet the FDA continues to approve it's use. Madness.
We are doomed. The greed will destroy us all.
Is it not possible to autopsy a dolphin?
education, been to our schools lately, do you speak spainish? aveage student reading level 4th grade. prime material for wars that we never win. toxic world.
its over, this earth, is done. radition,oil spills, dumping garbage, we are passed the point of no return, there is no way we will be able to clean this mess up, ever.
If we vote Mitt into office the off and on shore drill will just get worst and he doesn't care about green energy either.
when you say green energy do you mean companys like solnydra
Most investments succeeded. A few failed.
I hope that we can introduce a new form of educational system that will just help us live together period.
If we established an environment of mutual concern, responsibility, and guarantee -- we would inevitably come to be concerned, responsible guarantors for the planet.