Oil-eating bacteria don’t work in low oxygen water, dead zones
June 19th, 2010
Gulf oil full of methane, adding new concerns, Associated Press, June 18, 2010:
It is an overlooked danger in the oil spill crisis: The crude gushing from the well contains vast amounts of natural gas that could pose a serious threat to the Gulf of Mexico’s fragile ecosystem.
The oil emanating from the seafloor contains about 40 percent methane, compared with about 5 percent found in typical oil deposits, said John Kessler, a Texas A&M University oceanographer who is studying the impact of methane from the spill.
That means huge quantities of methane have entered the Gulf, scientists say, potentially suffocating marine life and creating “dead zones” where oxygen is so depleted that nothing lives.
“This is the most vigorous methane eruption in modern human history,” Kessler said.
The small microbes that live in the sea have been feeding on the oil and natural gas in the water and are consuming larger quantities of oxygen, which they need to digest food. As they draw more oxygen from the water, it creates two problems. When oxygen levels drop low enough, the breakdown of oil grinds to a halt; and as it is depleted in the water, most life can’t be sustained. …
In early June, a research team led by Samantha Joye of the Institute of Undersea Research and Technology at the University of Georgia investigated a 15-mile-long plume drifting southwest from the leak site. They said they found methane concentrations up to 10,000 times higher than normal, and oxygen levels depleted by 40 percent or more.
The scientists found that some parts of the plume had oxygen concentrations just shy of the level that tips ocean waters into the category of “dead zone” — a region uninhabitable to fish, crabs, shrimp and other marine creatures. …
In an e-mail, Joye called her findings “the most bizarre looking oxygen profiles I have ever seen anywhere.”