Gulf spill: Is the oil lurking underwater?
Between 20 April and 15 July, BP’s busted Macondo well released some 4.9 million barrels of oil into the Gulf of Mexico. Within weeks of the leak being plugged, researchers in the area reported on the oil’s rapid disappearance. Others are now challenging those early claims.
So is the oil gone or not?
At the surface, the oil does appear to be almost gone. But the big question is whether oil droplets are still around below the surface, and if so how long they will linger. Researchers are divided on this.
For months, the government and BP burned and skimmed oil off the surface. What’s more, hot temperatures boosted evaporation and microbial communities that consume surface oil. Estimating what’s going on further down the water column and in sediments along the sea floor – is much more challenging.
Of particular interest is the fate of enormous plumes of oil droplets that were seen near the broken wellhead when it was still gushing oil. Richard Camilli and colleagues at the Woods Hole Oceanographic Institute in Massachusetts show in a study out this week that at one point the plume was 2 kilometres wide and 200 metres high. But their measurements were made from 19 to 22 June, before the leak was plugged early this month (Science, DOI: 10.1126/science.1195223).
In another study published this week, Robert Hallberg of the National Oceanographic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, used models to estimate how long it would take the Gulf’s prevailing currents and oil-eating microbes to disperse and degrade the oil. He found that oil near the surface can abate within weeks, whereas oil trapped in the colder waters below about 1100 metres can take up to two months to disappear (Geophysical Research Letters, DOI: 10.1029/2010gl044689, in press).
Contrary to other reports, Camilli also found evidence that oil-munching bacteria were only slowly working through the suspended oil. Together, his and Hallberg’s studies suggest that oil will probably remain deep in the water column for at least another month.
But Terry Hazen, a microbial ecologist at Lawrence Berkeley National Laboratory in California, says that he has studied the same plume as the Woods Hole group. His results, which have yet to be published, show that microbes are rapidly eating up the plumes – so much so, he says, that the oil should already have vanished. Hazen is adamant: “The plume is no longer there. It’s gone.” Read full article