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Gulf of Mexico oil spillOil-eating bacteria responsible for oil plumes, dispersants vanishing

Published 5 August 2010

The plumes of dispersant and oil in the Gulf’s deep waters that were causing anxiety among biologists have gone away; scientists say the reason is oil-eating bacteria; the bacteria in the Gulf’s deeper waters may have reacted so fast thanks in part to being primed by natural oil seeps along the sea floor; given that oil stopped flowing two weeks ago, scientists say it is not surprising that the plumes are now largely gone

Oil consuming microbes such as the Munox above, made short shrift of the Gulf spill oil plumes // Source: innworldreport.net

Just two weeks after BP capped its broken Deepwater Horizon well, the plumes of dispersant and oil in the Gulf’s deep waters that were causing huge anxiety among biologists have gone away. This may mean concerns over the spill’s widespread environmental damage were exaggerated — though some ecologists remain cautious.

We can’t find oil at the surface and, as of this week, we cannot find it deep down either,” says Terry Hazen, a microbial ecologist at the Lawrence Berkeley National Laboratory in California, whose research has focused on the area within 100 kilometers of the wellhead.

Sujata Gupta writes that Hazen thinks he can explain why the plumes are gone. He had previously collected water samples from inside and outside of the plumes, which he kept at 4 °C— the coldest temperature along the floor of the Gulf. Within days, he found that the microbial populations in the samples began to shift in favor of those able to break down oil. The findings tally with those of other ecologists working in the field. Hazen also found that the oil disappeared faster still in the presence of Corexit 9500A, the dispersant used by BP in the Gulf waters.

Gupta writes that oil-eating bacteria in the Gulf’s deeper waters may have reacted so fast thanks in part to being primed by natural oil seeps along the sea floor. All things considered, and given that oil stopped flowing two weeks ago, says Hazen, it is not surprising that the plumes are now largely gone.

Further afield, others say the signs of the leak are lingering. Just a week ago “there was a sheen miles wide and long,” says coastal ecologist Michael Blum of Tulane University in New Orleans. “My impression is there’s plenty of oil still on the water and on shorelines – but not necessarily as thick as it once was.”

Nor does oil in water account for all of the spill. Andreas Teske of the University of North Carolina, Chapel Hill, points out that its less-degradable components, like the asphaltenes found in tar balls, may have sunk to the sea floor where they could stick around for months or years.

Moreover, the increase in microbes means more biomass at the bottom of the food chain, says James T. Hollibaugh at the University of Georgia in Athens. As these microbes consume oxygen, they could further harm species already affected by the spill, says Teske.

Gupta notes that some researchers see a lesson in the microbial studies. In future, oil companies prospecting new deep-sea sites should study the local microbial communities and prefer those primed for oil consumption, says Gary King, a microbial ecologist at Louisiana State University in Baton Rouge.

The findings may even provide some validation for BP’s controversial decision to release unprecedented volumes of dispersant into the Gulf, says King. By breaking up oil into droplets, dispersants will have provided microbes with greater access to their meal.

Some fear that the visible disappearance of the oil might detract from long-term research projects into the impacts of the spill. Last week, incoming BP chief executive Bob Dudley said it was time to scale back parts of the clean-up effort.

Hopefully, the oil’s disappearance does not “prove that we should be out there drilling more holes faster,” Hollibaugh says. “I think caution is warranted here.”

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