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Methane-Munching Microbes Hit Rock Bottom

Oct 15, 2014 02:19 PM EDT
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Certain methane-munching microbes have hit rock bottom, literally, living in rocks on the bottom of the ocean floor and soaking up large amounts of the potent greenhouse gas, according to new research.

These bottom-dwellers, described in the journal Nature Communications, are previously unknown methane sinks located in the deep sea, having such an effect that they impact global levels of the gas.

"We've recognized for awhile that the deep ocean is a sink for methane, but primarily it has been thought that it was only in the sediment," study researcher Jeffrey Marlow, a graduate student at Caltech, told Live Science. "The fact that it appears to be active in the rocks itself sort of redistributes where that methane is going."

According to the researchers, these microbes don't need oxygen to survive, but rather rely on sulfate ions present in the seawater for their energy needs. Their methane breathing system, the details of which still remain unclear, involves single-celled microorganisms dubbed "ANME" for "ANaerobic MEthanotrophs." ANME work closely with bacteria to consume methane using the ocean's sulfate.

"Without this biological process, much of that methane would enter the water column, and the escape rates into the atmosphere would probably be quite a bit higher," Marlow said in a statement.

The microbes, living in enormous rocks hundreds of feet tall, eat about 80 to 90 percent of the world's methane released through previously studied seeps, or cracks in the ocean floor.

Lead study author Victoria Orphan of Caltech and her colleagues found direct evidence of methane-breathing microbes in carbonate rocks collected from Hydrate Ridge, off the Oregon coast, as well as from cold seeps in Costa Rica and off the coast of northwestern California.

According to DNA analysis of rock samples, even though the microbes consumed methane at a slower rate than their sediment-dwelling cousins, there are presumably so many more microbes in the rock than in the dirt, its impact on global methane levels may be more significant.

Like notorious carbon dioxide, methane is a greenhouse gas capable of trapping heat from the Sun in the Earth's atmosphere. Though carbon dioxide (CO2) is more abundant, methane is actually 80 percent more potent at trapping heat than CO2.

And these methane-eating microbes, though out of site in the deep ocean, may be vital to reducing methane's role in global warming.

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