Green Blog: Scientists Solve the Paradox of Why Oeans Exude So Much Methane

Four percent of the methane found in the earth?s atmosphere comes from oceans. But for decades, researchers have been flummoxed by how that could be. The only known biological source of methane is a class of microorganisms that produce methane when they are alive but die when exposed to oxygen. How could these microorganisms, called methanogens, be so plentiful in the oxygen-rich ocean?

A new paper?in the journal Science proposes a plausible explanation for this seemingly impossible reality, which is known as the ocean methane paradox.

To back up a bit: in 2008, David Karl, a researcher at the University of Hawaii, and Edward DeLong, a researcher at M.I.T., had proposed that marine microbes, always starved for phosphorus, can use methylphosphonic acid to obtain this nutrient. Methane is a byproduct of their absorption of phosphorus.

The glaring problem was that methylphosphonic acid had been found only in chemical research labs, not in nature.

William Metcalf, a professor of microbiology at the University of Illinois and the principal investigator for the article published in Science, did not set out to explain the ocean methane paradox. His lab was trying rather to discover new antibiotics for fighting pathogens that are resistant to multiple drugs.

Specifically, he was hunting for a class of molecules found in nature, phosphonates, which have great pharmaceutical potential. The research involved scanning genome sequences in search of particular genes that are known to be associated with the production of these compounds.

Dr. Metcalf thought he had found a promising source of phosphonates in?Nitrosopumilus maritimus, one of the most common organisms in the ocean. But the researchers found that one of its genes didn?t actually produce phosphonates, but methylphosphonic? acid.

The discovery goes a long way to providing the missing piece of the ocean methane puzzle. ?Yes we?ve solved an interesting little mystery,? Dr. Metcalf said. ?But I think it?s much more than that.?

While 4 percent of the world?s methane ?doesn?t sound like a lot,? he said, methane is 20 times as potent as carbon dioxide as a greenhouse gas. Understanding the sources of methane and where it is stored is therefore critical in accurately assessing climate changes, he explained.

Dr. Metcalf pointed out that some scientists have advocated fertilizing the ocean to stimulate the growth of algae that would absorb carbon dioxide. But it?s ?really essential to fully understand the system before you even think about manipulating it,? he said.

?One of the things you would use to fertilize the ocean is phosphorus,? he said. ?More phosphorus in the ocean would mean that microbes wouldn?t break down methylphosphonic acid to get at it, so perhaps less methane would be produced.?

Dr. Metcalf said said he was not advocating a solution like adding phosphorus to the ocean, but emphasizing the importance of fully understanding the processes by which methane is produced.

Source: http://green.blogs.nytimes.com/2012/09/04/solving-the-ocean-methane-paradox/?partner=rss&emc=rss

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