Editor'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.

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