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Deepwater spill survey: Contaminated Gulf kills thousands of sea cucumbers

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


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Texas A&M, sea cucumber, DeepwaterEditor’s Note: A team of researchers led by John Kessler, Texas A&M College of Geosciences chief scientist and assistant oceanography professor, has traveled to the Deepwater Horizon disaster site to study the methane leaking into the Gulf of Mexico (along with tens thousands of barrels of crude oil) daily at the site of the damaged Macondo 252 well. Kessler, along with David Valentine (a professor of marine sediment geochemistry, biogeochemistry and geomicrobiology at the University of California, Santa Barbara) and the rest of his colleagues are hoping to come away with a rough estimate of the spill’s size by the time his team returns home on June 20, followed by more accurate estimates as they complete their analysis of the information collected. Other objectives of the expedition onboard the RV Cape Hatteras include trying to determine how the methane might be removed from the water (whether eaten by waterborne microorganisms or released into the atmosphere) and how methane concentrations will change over time. Rainer Amon, a Texas A&M associate professor of marine sciences and oceanography, filed the following dispatch. This is the team’s second blog post for Scientific American.



Monday, June 14, 2010


This is our second day at sea in the general area of the Deepwater Horizon oil spill. So far we have kept about seven miles [11 kilometers]  away from the epicenter of the spill. My role during this cruise is to trace the subsurface plume of oil and gas using a sensor that measures fluorescence bouncing back from certain dissolved molecules with polyaromathic hydrocarbons being one of them. Using this sensor along with other measurements like dissolved oxygen and light transmission we readily located a subsurface plume to the southwest of the spill.

The dimension of the plume, which is located at a depth of 1,100 meters, is about seven kilometers wide and about 50 meters tall. We don’t know yet what the concentration of hydrocarbons is in this plume is, but my colleagues will certainly put a number on this feature soon. The next few days we will continue to use the sensors to follow the plume and look for other plumes to the south and east of ground zero.

Texas A&M, Deepwater, sea cucumber

Starting yesterday night we have been seeing a large number of dead sea cucumbers floating on the surface. These animals live on the bottom of the ocean where they feed on sediment and suspended organic matter. I would estimate the number of dead sea cucumbers to be in the thousands and their cause of death is obviously related to the oil spill. Possible causes include direct contact with oil, the dispersant or oxygen depletion as a result of the spill. A detailed study of the benthic environment is necessary to get a detailed picture of the damage done to this environment and how it affects the ecological condition of the Gulf of Mexico.

Image of dead sea cucumbers on the surface of the Gulf of Mexico near the Deepwater site courtesy of Rainer Amon



Close-up image of a sea cucumber courtesy of Benutzer:Cubanito, via Wikimedia Commons





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  1. 1. Mike Selene 2:30 pm 06/15/2010

    "their cause of death is obviously related to the oil spill"

    Unless the scientific method has been temporarily suspended in the Gulf of Mexico, these sea cucumbers "likely " died as a result of the spill. Rainier, and all writers should be clearer in their separation of conjecture and evidence supported supposition.

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  2. 2. Mikekerr 6:33 pm 06/15/2010

    Good report Rainer, keep on top of this – Texas could be next or a hurricane could put this in our lap. Obviously an analysis of dead sea cucumbers is appropriate along with random water samples inside and outside the plume at various depths to find out what other organisms might be affected. Both animal and plant life.
    Would be ideal to know if it were effects from the oil, gases or the chemical dispersants. I have heard nothing from EPA or BP that stated the dispersants were pre-tested and labeled for this use? Why not – even garden herbicides or water weed chemicals are tested and labeled? How would they affect any possible ship based or land desalination process – toxic or not?
    Should we be now rapidly growing and more intensively studying all ocean microbes which feed upon and break down petroleum chemicals? That would seem wise, especially in the area of sensitive wetlands, marshes, fish/shrimp nurseries or oyster beds. The huge difference in climate, water temperature and environment between the Valdez incident and LA would seem to make bioremediation a very helpful process.

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  3. 3. doug123sa 9:39 pm 06/15/2010

    Oh please, the scientific method requires skepticism not silliness. The timing and location of the mass killings are painfully unlikely to be coincidence. Regardless, you offer no reason that "likely" is more appropriate than "obviously" — both indicate probability and opinion.

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  4. 4. rumurd 10:41 pm 06/15/2010

    We are talking about far more than the scientific method here but the ongoing credibility of scientific commentary. As the climate change debate has shown, science has to tread carefully in separating belief from fact. While the oil-spill may be the obvious and likely cause of the sea cucumber mortality, scientists must still be careful about adopting a swaggering certainty in the absence of definitive data. Such moral conviction creates scope for abuse and can lead to other, less rational, conclusions and opinions being proferred with the semblance of scientific authority.

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  5. 5. Abadavas 12:38 am 06/16/2010

    Dr. Kessler can you measure the cavication of the plumes generated by the vent? What’s the potential of the loss of bouncy on the sea surface surrounding the blowout?

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  6. 6. coastalaggie 2:13 pm 06/16/2010

    Is there a plan to measure water column toxicity? If so, what method(s) do you plan to use?

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  7. 7. Hawaii woman 3:38 pm 06/16/2010

    In Hawaii, each sea cucumber hosts it’s own crab and fish. The hosts death indicates their death too.

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  8. 8. Neptunerover 5:05 am 06/17/2010

    All those floating dead sea cucumbers; it’s like a Biblical sign.

    How much dead stuff rises to the surface anyway? No doubt there’s much more death hidden under the surface. Nothing with a shell is going to float.

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  9. 9. Musty 9:48 pm 06/17/2010

    I agree 100% that the scientific community should be clearer in their separation of conjecture and evidence supported supposition.

    As far as we know all the water fowl that are covered in crude oil probably got that way from working at Jiffy Lube.

    Best part is high levels of refined oil is being detected in the Gulf water now getting there from peeps who are taking advantage of the situation and dumping it, oh wait those careless water fowl are at it again.

    Peace out

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  10. 10. dsurf 1:56 am 06/18/2010

    Is the mass die-off of sea cucumbers more likely attributed to the oil or the dispersants? It would be interesting to note whether this reduction in population is occurring farther afield from the spill. I have personally witnessed an unusually large number of dead sea cucumbers on local Florida beaches, but all signs thus far indicate the Loop Current has not yet pulled these toxic products to Miami. What does long-term flow modeling look like for spread of the COREXIT into the environment?

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  11. 11. rmwamon 7:07 pm 06/26/2010

    Since I was the source of the initial report on the mass mortality of sea cucumbers here is some clarification after our unfortunate loss of communications during most time of the expedition. I finally managed to catch some of the half decomposed specimen from the oil slick and after looking at them closely it turned out they are in fact mesopelagic (living at depth between few hundred to a 1000 m) larvaceans of the species Pyrosoma atlanticum. Those animals are not familiar to most people due to their remote habitat, they can occur in large numbers at depth and usually sink to the sea floor after dying. In this case however, they floated to the top in large numbers which remains a mystery. Cause of the mass mortality is not clear (not the focus of our expedition) but along with chemical (toxic) causes we need to consider physical causes (accumulation of gas in their body cavities and subsequent increased buoyancy). In either case I would reiterate that the cause of death for those larvacaeans has something to do with the change in the physical or chemical environment around the former DH platform inflicted by the accident.

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