Methane-Generating Microbes In Arctic Lake Sediments

A new study finds that in scenarios of increasing global temperatures, methane-generating microbes, found in thawing lake sediments may ramp up production

Though methane stays in the atmosphere for far less time than CO2, it is 25X more potent during that period. Concerns about methane have risen because of concerns about possible leaks due to increased natural gas, which produces far less CO2 than coal, and that methane may be released as climate changes.

Researchers found that the methane detected in in lake sediments in this region can arise from both ancient theremogenic sources deep in the earth, or from shallow contemporary biological sources. Interestingly, the coastal plain inthe NorthSlope of Alaska is estimated to contain 53-billion cubic feet of natural gas trapped under the permafrost ice cap.The work inGeobiologyillustrates how the decomposition of organic matter in thermokast lake sediments can produce up to three times more biological methane gas emissions when subjected to increased temperatures in a simulated environment.

Thermokarst lakes occur as permafrost thaws and creates surface depressions where meltwater accumulates , converting what was previously frozen land into small freshwater lakes with active decomposing sediment layers. Methanogensis from microbial communities found in these changing environments has been less studied than direct emissions

"The large amount of organic matter stored in the thaw layer between the water column and the permafrost table serves as a significant source of carbon for methanogensis," explained Paula Matheus Carnevali, a doctoral student at Nevada's Desert Research Institute and the study's lead author. "Identifying and understanding the production sources of methane will improve our ability togenerateaccurate predictions about the changing climate in the Arctic."

The study focused on methane dynamics within 16 sediment cores collected over a period of four years from two Alaskan thermokarst lakes, near Barrow, Alaska. Samples were obtained from three sites, one proximal to an active, submerged natural gas seep and another from a site approximately one-kilometer away from the seep site. The second lake was located about 13-km to the northwest, and did not have visibly active seeps.

Source: Science 2.0

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