Yahoo News 6 Jan 11;
WASHINGTON (AFP) – The huge quantity of methane released in the Gulf of Mexico last year during the worst oil spill in US history was ingested by bacteria in four months, according to a scientific study published Thursday.
Methane made up 20 percent of the huge plume of crude oil that escaped from a broken pipeline nearly one mile (1,600 meters) below the Gulf surface, after the BP-operated Deepwater Horizon platform exploded on April 20, killing 11 workers.
The leak, the worst oil spill in US history, was finally plugged on July 15, after spewing millions of gallons of crude into the Gulf.
"The methane was completely consumed by early September... it happened very quickly and it was a surprise to us," University of California Santa Barbara geochemistry professor David Valentine told AFP.
Valentine, one of the lead authors of the study in Thursday's edition of the journal Science, said the rapid "digestion" of the methane by bacteria showed the vital role microorganisms likely play in preventing greenhouse gases at the bottom of the ocean from entering the earth's atmosphere and contributing to global warming.
"They do serve an important function, and as we see here under certain conditions these bacteria can be very effective at preventing the methane from reaching the atmosphere," he added.
Valentine said research he published in September-October showed that other species of bacteria also consumed the ethane and propane released by the blast.
Bacteria also consumed some of the crude oil that was spilled in the Gulf, but researchers have yet to determine the quantities, he said, adding that chemical dispersants facilitated its absorption by the microorganisms.
In contrast to crude oil, methane and other gases naturally dissolve in ocean water before they are ingested by bacteria.
Gulf of Mexico oil leak may give Arctic climate clues
Richard Black BBC News 6 Jan 11;
Almost all of the methane released in the Gulf of Mexico oil leak was quickly swallowed by bacteria - which may give clues to climate change in the Arctic.
Writing in journal Science, US researchers report that methane-absorbing bacteria multiplied in the Gulf following the April accident.
The Arctic contains vast stores of methane, and its release could quickly accelerate warming around the world.
But scientists caution that the regions are very different.
The research ship Pisces, operated by the National Oceanic and Atmospheric Administration (Noaa), made several voyages into the Gulf in the months following the leak.
"There were thousands of different types of molecule coming out of the well, and by far the most abundant was methane," said research leader John Kessler, from Texas A and M University.
"In fact, by weight, 30% of it was methane.
"Normally we have to go around and study what's seeping naturally out of the sea floor; but this release was massive and localised."
Virtually all of the methane remained suspended and dissolved in sea water at depths of around one kilometre.
Bacteria in the water that have evolved to process naturally-seeping methane apparently increased in number, taking oxygen from the water as they did so, and mopping up the Deepwater Horizon's cargo.
The team's calculations indicate that less than one hundred thousandth of the gas released made it into the atmosphere.
Warming warning
Methane is the second most important gaseous component of the man-made portion of the greenhouse effect.
And vast quantities of it - no-one knows how much, though some estimates put it as 3,000 times the current amount in the atmosphere - lie trapped in the sea bed around the Arctic. There are other deposits around the world as well.
Some see this methane hydrate as a potential future energy source.
Others fear that if it escapes as the seas warm, it will act to amplify global warming.
In principle, the Deepwater Horizon research could help inform scientists about how serious methane releases could be - how much would be processed in sea water, and how much would make it into the atmosphere.
"In the Arctic, there definitely would be some sort of microbial response; and in most places on the sea floor that have the capacity for massive release, there will be some seepage that will help to populate the water with microbes that could respond," Dr Kessler told BBC News.
However, he cautioned, there are big differences between the Gulf of Mexico leak and potential methane sources in the Arctic.
Ed Dlugokencky, who runs Noaa's global registry of methane concentrations but was not involved in the Gulf research, agreed.
"The implications of this work for release of methane from hydrates likely only applies to deep waters, not areas where hydrates exist on shallow continental shelves such as the East Siberian Arctic shelf," he said.
"There, water is only about 40m deep, and bubbling is an important mechanism for transport of methane from the sediments to the atmosphere."
The shallower the water, the less time methane would spend in it, making absorption less likely. Temperature, currents and the types of bacteria present could be other factors important in determining how much makes it into the atmosphere.
However, Dr Dlugokencky noted that evidence of vast, rapid releases of methane from the sea floor has not been seen in ice-core records, which now trace Earth history back about 800,000 years.
Research ships make regular cruises to the Arctic and have regularly found evidence of methane bubbling into the atmopshere.
But, said Professor Graham Westbrook from the UK's University of Birmingham, there is still a lot of basic science to be done.
"We don't know the distribution of the methane hydrates - we don't know how pervasive they are in the region," he said.
"And in places like the shelf areas north of Siberia, where releases have been found, it's not clear how much of this is coming from the sea bed and how much is brought into the sea by rivers.
"Also, we don't know how much of the releases we see are down to anthropogenic warming in the last couple of centuries, and how much relates to the natural warming we've seen since the end of the last Ice Age."
