A rosy scenario unfolds in gulf
WASHINGTON - Federal scientists are reporting the best possible scenario unfolding for BP's leaked oil in the Gulf of Mexico: Microbes are munching the underwater oil, but the process is not robbing the waters of too much oxygen and creating "dead zones" for marine life.
Oxygen levels in some places where the oil spilled are down by 20 percent, but that's not nearly low enough to create zones where fish can't live, according to a 95-page report released Tuesday.
In an unusual move, BP released 771,000 gallons of chemical dispersant at the leaking wellhead, about a mile deep, instead of just on the water surface, to break up the oil into tiny droplets.
That has made it easier for the oil-eating microbes to do their job, though scientists hoped the oil was not degrading at a rate that would cause problems with lack of oxygen.
"Has it hit the sweet spot? Yes. Was it by design? Partly," said Steve Murawski, the National Oceanic and Atmospheric Administration senior scientist who headed the federal team.
Oxygen levels would have to drop an additional 70 percent for waters to be classified as dead zones, he said.
The Gulf of Mexico already has a yearly problem with a dead zone - the size of Massachusetts this year - caused by farm runoff moving down the Mississippi.
Federal officials had been tracking oxygen levels and use of chemical dispersants since the oil spill. Had the oxygen plummeted to near-dangerous levels, the dispersant use would have been stopped, said Greg Wilson, science adviser at the Environmental Protection Agency's emergency management office.
Dispersant use is the subject of fierce debate. While dispersants make it easier for bacteria to degrade the oil, they also tend to hide oil below the surface, leading to concerns about toxicity.
One reason oxygen levels haven't dropped too low in areas where dispersants were used is because of natural mixing in the gulf, which keeps bringing oxygen into areas with lowered oxygen levels, Murawski said.
There are indications bacteria are eating the oil thousands of feet underwater because oxygen levels have sagged at those depths. The finding also lends weight to claims last month by the government that much of the oil has degraded, dissolved, or evaporated, Murawski said.
The new work is based on data collected from May through August at 419 locations by nine government and private research ships.
Larry McKinney, director of a Gulf of Mexico research center at Texas A&M University in Corpus Christi, said the new federal data showed that it was a "nearly perfect" outcome. McKinney was not involved in the report.