Food galore
January 7, 2011
Methane made up nearly a fifth of the huge plume of pollution that escaped from BP's broken pipeline in the Gulf of Mexico last year.
Yet within four months of the disaster, bacteria had eaten most of this powerful climate-warming gas before it had the chance to make its way into the atmosphere, according to the study published this week in the journal, Science.
"The methane was completely consumed by early September," said David Valentine, one of the study's lead authors, in an interview with the AFP news agency. "It happened very quickly and it was a surprise to us."
Methane's role in the Gulf spill
The Gulf of Mexico oil spill was triggered when BP's Deepwater Horizon rig exploded and sank in April last year, killing 11 people on board.
A damaged well head on the sea floor was only plugged months later in July.
Some 4.9 million barrels of crude oil escaped, including 200,000 tons of methane, the most abundant of the hydrocarbons released in the disaster.
In comments to Reuters, Valentine, a geochemistry professor at the University of California Santa Barbara, said the spill served as a kind of "accidental experiment" for observing how ecosystems respond to large injections of methane.
In this case, bacteria that feed on methane jumped in population in response to the sudden surge of available food.
"Given observations about how slowly methane is normally consumed, we didn't think the (bacteria) population was up to the challenge at all ... we thought it would be a lot slower," he said.
Implications for climate change?
This could prove to be good news in the struggle to limit climate change.
Many scientists are concerned about the enormous quantities of methane currently stored below the planet's oceans.
Methane is a greenhouse gas which has about 20 times the warming potential of carbon dioxide once in the atmosphere.
It is feared that if sea temperatures rise sufficiently, vast amounts of frozen methane on the sea floor could escape, leading to runway increases in global temperatures.
Some scientists hypothesize that this was the cause of a large increase in global temperatures around 55 million years ago, yet the findings from the Gulf of Mexico oil spill suggest the release of methane may not happen as swiftly as first thought.
Yet Valentine was cautious about extrapolating too much from the team's findings.
"Our work provides needed context to the arguments surrounding methane hydrates, but does not exclude competing processes," he told Deutsche Welle.
Other effects include depletion of oxygen in water
Scientists have also been keen to observe the side effects of microbes breaking down the oil spill.
One of these is the depletion of oxygen in the water, know as hypoxia.
The rapid growth of bacteria in marine environments often leads to oxygen depletion and so-called dead zones where other marine species cannot survive.
These can often be found in waterways polluted with agricultural runoff, especially fertilizers that encourage blooms of micro-organisms.
Yet this doesn't appear to have been so severe following the Gulf oil spill. Although some one million tons of dissolved oxygen were depleted, the phenomenon happened across a sufficiently wide area to avoid hypoxia.
Author: Nathan Witkop (AFP, Reuters)
Editor: Cyrus Farivar