What Lies Beneath

Research team finds large amounts of “degraded” oil in Gulf

10-04-2010 // Craig Guillot
Leilani Munter

A research team from Columbia University recently discovered large traces of degraded oil deep in the water column of the Gulf of Mexico. While this oil is in a less toxic form, experts say it still has the potential to cause “sub-lethal” effects that could impact the microbial ecosystem. And the worst part is that its real impacts may not be known for years to come.

The research team was lead by Ajit Subramaniam, an Associate Research Professor from the Lamont-Doherty Earth Observatory at Columbia University. The team traveled by vessel from August 21 through September 16 to a series of stations starting at the wellhead itself then going 100 miles southeast and backtracking 40 miles to the west. Using optical tools and fluorescents, the team set out to determine if there were oil plumes in the water and how deep oil was in the Gulf. Subramaniam said they found areas where “degraded” oil appeared to be present from as shallow as 100 meters from the surface all the way down to 1,200 meters below the surface.

“We found these in several layers and we often found layers stacked upon one another. A lot of the degraded oil appears to be moving around the Gulf, perhaps in different directions,” said Subramaniam.

Impacts May Not Be Known for Years

Subramaniam stresses that all of the oil is “degraded” and in a more diluted form. The team did not find any traces of what one might think of in terms of fresh, thick oil. While that is good news and lessens the blow of direct impacts on wildlife through toxicity and consumption, Subramaniam said the impacts from the degraded oil could take years to be known.

“Just because it is degraded doesn’t mean it has gone away. The risk to wildlife now is bioaccumulation and that will take place over a much longer time frame. I think we’ll have to watch this over the next four or five years,” said Subramaniam.

Doug Inkley, senior wildlife biologist with the National Wildlife Federation, said that the oil, even in its current degraded form continues low level exposure to organisms in the environment. These sub-lethal effects can have long-lasting impacts on birds and aquatic species that can take years to unfold and discover. Inkley points to a Canadian study where captive mallards were given small amounts of oil. The birds would go through their feeding cycle and exhibit normal behaviors but did not produce fertile eggs as sub-lethal neurological effects caused their mating behaviors to change.

Lessons from Exxon-Valdez

Inkley also points to Prince William Sound where two decades after the Exxon-Valdez disaster, the herring population has yet to rebound. Inkley said that in the first year of the Alaskan disaster, everything appeared to be fine with the herring. After four years, there was a major population crash and data reveled that during the year of the spill, the reproduction rate had dropped dramatically.

“The question is, what sub-lethal effects is the oil going to have on the hundreds of organisms that are exposed to it?” said Inkley.

Subramaniam also added that the team found evidence of an “oily snow” that had fallen on the sea floor in some areas. While the toxicity of oil can be minimized as it is diluted, he also expressed concern about the natural gas and methane that is potentially being consumed by such microbes.

“I would like to see over time if there has been a fundamental shift in the microbial ecosystem and if the bacteria populations in the Gulf of Mexico have shifted. We’re going to have to watch this,” he said.

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