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Researcher to shed more light on methane-making microbes in Arctic permafrost

Tuesday, April 30, 2013

LAWRENCE — As our globe continues to heat up, one grim threat to humanity — and indeed much of the planet’s biology — is the danger of increased levels of methane in the atmosphere from thawing Arctic permafrost and the rapid release of methane pockets in shallow ocean sediments. That’s because methane is a greenhouse gas 20 times more powerful than carbon dioxide over a 100-year period, according to the Environmental Protection Agency. But how likely is this scenario?

Jennifer Roberts, associate professor of geology at the University of Kansas, is researching the impact that an increase in temperature will have on microbes that inhabit permafrost. Permafrost is rich soil, rock and sediments that have been frozen for thousands of years. As it thaws due to climate change, methane trapped within the permafrost is transferred into the atmosphere. What’s worse, microbes revived in the warming soil could generate even more methane over time as they break down organic matter.

“Methane is being cycled between two types of microorganisms — methanogens, which are producing the methane, and methanotrophs, which are the organisms that use that methane as an energy source,” Roberts said. “Theoretically, methanotrophs should have higher rates of metabolism and suppress methane flux. What we found with our early work was unfortunate — these methanotrophs are nutrient-limited, and there’s no way that they can utilize this excess methane. They’re already at their maximum abundance and activity. So as methane increases, we’re going to see all of those increases go directly to the atmosphere.”

Now, Roberts is studying whether methanogens, due to limits in nutrition in Arctic soils, could be likewise restricted in their methane-generating activity. The answer to this question will be critical in modeling the amount of methane that melting permafrost might generate. Until now that answer has been hazy, even though the consequences are critical to accurately predicting methane release and its impact on global climate.

“Are the methanogens nutrient-limited?” asked Roberts. “Can we expect that they are going to run into that same limitation as the methanotrophs, in which case we have a balanced, steady-state cycling of the methane between these two groups? Or, are methanogens more efficient in regard to their nutrient needs?”

To answer these questions, Roberts will trek to the European Arctic field station in Ny-Ålesund, Svalbard, this August. On that frozen Norwegian island, she will collect the most comprehensive samples ever of soils to characterize key geochemical properties, methane concentrations, depths of the microbes’ activity in the soil and a host of other facets.

Collaborating with David Graham and Neil Gray from Newcastle University in the United Kingdom, the KU researcher will sample more sites than any previous project, with the eventual aim of giving climate modelers stronger data on the likely methane production of these arctic microorganisms.

The largest unknown in climate projections revolve around feedbacks that can help accelerate or regulate current warming. Roberts’ findings will help constrain these feedbacks for methane cycling.

“Our results are consistent with data that shows that methane release is increasing in the Arctic. If there are no moderating effects, such as limitation on production, it reinforces a need to reduce anthropogenic methane production," she said.

The National Science Foundation is supporting Roberts’ research with a two-year, $51,500 award.

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