Last month I wrote about the two-inch layer of “slime snot” that scientists found on the floor of the Gulf of Mexico 16 miles from the site of the Deepwater Horizon blowout. I learned about this discovery from Vernon Asper, a professor of marine sciences at the University of Southern Mississippi, during a private briefing at Stennis Space Center. At the time, Asper and his colleague Samantha “Mandy” Joye, a professor of marine sciences at the University of Georgia, were awaiting an analysis of the gooey material.
“We can’t absolutely say that it’s oil,” Asper told us. “But it sure looks like oil, it smells like oil, and it is not found great distances from the well site.”
Now, according to a prominent geochemist, there’s substantial evidence that the sediment beneath the Gulf is indeed contaminated with oil from the BP disaster -- a finding that has put the somewhat forgotten spill back in the news again.
Yesterday I talked by phone with David Hollander, an associate professor of chemical oceanography at the University of South Florida. Hollander was speaking from aboard the R/V Weatherbird II, a research vessel that is exploring the northern Gulf looking for contamination from the spill. Hollander’s crew has been taking sediment-core samples 20 to 26 nautical miles north and east of BP’s Macondo well, in the region of DeSoto Canyon, a nutrient-rich erosional valley off the Florida coast. His research zone is located farther from the well than Joye and Asper’s, and in the opposite direction.
Last August Hollander used an oil-patch trick from the 1930s: He shone an ultraviolet light on the sediment. “It reflected back at us like a constellation of stars,” he says -- an observation he calls “consistent with the settling of a fine mist of oil microdroplets.”
A molecular analysis showed that the fluorescing particles were indeed petroleum hydrocarbons. But did they come from the Macondo well?
To find this out, Hollander performed a test called compound-specific isotope analysis. “We can measure the concentration of different types of carbon atoms to develop a fingerprint on over eight separate compounds,” he explained. Earlier, he had used this method to determine that the chemical signature of the oil in the Gulf’s underwater plumes matched that of the oil from the BP spill. This time he applied the analysis to the sediment goo.
“Geochemists are very prudent,” he said. Without molecular proof, “we were very reluctant to say it was BP oil.” But when Hollander performed the analysis -- the results have just come back, he says -- “it was a perfect match. Probability-wise, for one to match that kind of fingerprint by chance would be miraculous.”
Hollander described the layer as “rubbery, almost gelatinous” -- a mixture of oil and bacteria feeding on it. “There’s no doubt the microbes are working their way through the oil,” he said. “That doesn’t mean the material isn’t toxic.” Even if it’s below government toxcity standards, he says, it can have debilitating effects -- weakening fish, for example, so they’re more vulnerable to predation. Length of exposure matters too: “If you’re contaminated by these chemicals for a long time, even if the concentrations are low, they can have an effect.”
Exactly what that effect is. scientists don’t know yet. Hollander is particularly anxious about small organisms at the bottom of the food chain, including fish eggs and fish larvae. Already a marine bacteria and a one-celled marine dinoflaggellate east of Macondo have shown “very, very repressed” photosynthesis, he says.
Hollander also worries because 2010 has been a year of strong “upwelling” -- movement of water away from the coast -- “which will dose the upper continental slope and shelf with hydrocarbon contaminants.” Hollander plans to keep monitoring the damage; he will be making research trips into the Gulf for the next 16 months.