NEW ORLEANS — Vast amounts of natural gas contained in crude escaping from the blown Gulf of Mexico oil well could pose a serious threat to marine life by creating "dead zones" where oxygen is so depleted that nothing lives.
The danger presented by the methane has been largely overlooked, with early efforts to monitor the oil spill focusing on the more toxic components of oil. But scientists are increasingly worried about the gas that can suffocate sea creatures in high concentrations.
At least 4.5 billion cubic feet of natural gas — and possibly almost twice that amount — have leaked since April 20. That's based on estimates from the U.S. Geological Survey's "flow team" that 2,900 cubic feet of natural gas are escaping for every barrel of oil.
"This is the most vigorous methane eruption in modern human history," said John Kessler, a Texas A&M University oceanographer.
Scientists, including those working with the flow team, estimate that methane makes up between 40 percent and 70 percent of what is spilling into the Gulf.
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.
Methane is a colorless, odorless and flammable substance that is a major component in the natural gas used to heat people's homes. Petroleum engineers typically burn off excess gas attached to crude before the oil is shipped off to the refinery. That's exactly what BP is doing with gas it started capturing from the leak 15 days ago.
A BP spokesman said the company was burning about 30 million cubic feet of natural gas daily on a ship at the surface, adding up to about 450 million cubic feet since the containment effort started.
But that figure does not account for gas that eluded containment efforts and wound up in the water, leaving behind huge amounts of methane. Scientists are still trying to determine how it could damage the Gulf and its creatures.
The high-pressure seafloor leak is spewing like a fire hose, causing oil and gas to dissolve into tiny droplets that are less likely to rise to the surface. Adding to the effect, more than a million gallons of chemical dispersants have been pumped into the gusher by BP — a bid to stop oil from reaching the coast that comes at the expense of the Gulf's deeper waters.
The National Science Foundation funded research on methane in the Gulf amid concerns about the depths of the oil plume and questions what role natural gas was playing in keeping the oil below the surface, said David Garrison, a program director in the federal agency who specializes in biological oceanography.
"This has the potential to harm the ecosystem in ways that we don't know," Garrison said. "It's a complex problem."
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.
Kessler has encountered similar findings. Since he began his on-site research on Saturday, he said he has already found oxygen depletions of between 2 percent and 30 percent in waters 1,000 feet deep.
Shallow waters are normally more susceptible to oxygen depletion. Because it is being found in such deep waters, both Kessler and Joye do not know what is causing the depletion and what the impact could be in the long- or short-term.
In an e-mail, Joye called her findings "the most bizarre looking oxygen profiles I have ever seen anywhere."
Representatives of the National Oceanic and Atmospheric Administration acknowledged that so much methane in the water could draw down oxygen levels and slow the breakdown of oil in the Gulf, but cautioned that research was still under way to understand the ramifications.
"We haven't seen any long-term changes or trends at this point," said Robert Haddad, chief of the agency's assessment and restoration division.
Haddad said early efforts to monitor the spill had focused largely on the more toxic components of oil. However, as new data comes in, he said NOAA and other federal agencies will get a more accurate read on methane concentrations and the effects.
"The question is what's going on in the deeper, colder parts of the ocean," he said. "Are the (methane) concentrations going to overcome the amount of available oxygen? We want to make sure we're not overloading the system."
BP spokesman Mark Proegler disputed Joye's suggestion that the Gulf's deep waters contain large amounts of methane, noting that water samples taken by BP and federal agencies have shown minimal underwater oil outside the spill's vicinity.
"The gas that escapes, what we don't flare, goes up to the surface and is gone," he said.
Steven DiMarco, an oceanographer at Texas A&M University who has studied a long-known "dead zone" in the Gulf, said one example of marine life that could be affected by low oxygen levels in deeper waters would be giant squid — the food of choice for the endangered sperm whale population. Squid live primarily in deep water, and would be disrupted by lower oxygen levels, DiMarco said.
Brown reported from Billings, Mont.
Copyright © 2010 The Associated Press. All rights reserved.
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