Methane beneath the Greenland ice sheet shapes microbial life and influences the carbon cycle

A new study involving researchers from the Faculty of Science, Charles University, Prague, shows that methane concentration is among the key factors determining the composition of microbial communities at the margin of the Greenland Ice Sheet. The findings, published in Applied and Environmental Microbiology, provide new insights into processes that influence carbon and methane cycling in a rapidly warming Arctic.

Beneath Greenland’s vast ice cover lies a surprisingly active microbial world. Microbial communities living in sediments beneath the ice are involved in the production, consumption and transformation of methane (CH₄). New research shows that the amount of methane available may play a major role in determining which microbial communities develop in this environment.

The research team analyzed microorganisms in glacial runoff along an approximately 2,000-kilometer (1,200-mile) transect of the western margin of the Greenland Ice Sheet. Concentrations of dissolved methane varied dramatically between sites, ranging from approximately 0.4 to 50,000 nanomolar, spanning five orders of magnitude.

The researchers therefore investigated whether this striking variation was associated with differences in microbial community composition and whether methane could serve as an important source of carbon and energy for microorganisms in these environments.

Methane as an organizing force in microbial life

Using 16S rRNA gene sequencing, the researchers characterized microbial communities in glacial runoff. The communities were dominated by the genera Rhodoferax, Polaromonas, Methylotenera and Crenothrix. The latter represents an important group of microorganisms capable of using methane.

Statistical analyses showed that the concentration of dissolved methane was the strongest identified predictor of microbial community composition along the studied section of the Greenland Ice Sheet.

“The results also revealed a link between microorganisms involved in the degradation of complex organic matter and those participating in methane cycling. This suggests that interconnected microbial processes beneath the ice indicate an active carbon-processing network in this environment,” says Lia C. P. Wentzel, corresponding author of the study from the Faculty of Science at Charles University.

Methane as a strong environmental selection factor

The study also revealed a marked difference between sites with low and high methane concentrations.

At sites where dissolved methane concentrations exceeded approximately 4.9 nanomolar, microbial communities showed a stronger signal of what ecologists call homogeneous selection. In other words, environmental conditions played a greater role in determining which microorganisms were able to thrive.

At sites with lower methane concentrations, stochastic ecological processes played a greater role, particularly ecological drift and limited dispersal of microorganisms between individual locations.

The findings therefore suggest that methane availability is not merely a consequence of microbial activity beneath the ice but is also an important factor in shaping the microbial communities themselves.

An important piece of the Arctic carbon cycle

Methane is a potent greenhouse gas, and understanding its production, consumption and transport in polar regions is important for understanding the Arctic carbon cycle. The new study shows that microbial life hidden beneath the ice also needs to be taken into account when investigating methane dynamics at the Greenland Ice Sheet.

These microorganisms are not merely passive inhabitants of an extreme environment. They actively participate in the transformation of carbon and methane, while their own communities are simultaneously shaped by the amount of methane available to them.

The study thus contributes to a better understanding of how microbial ecosystems at the margins of the Greenland Ice Sheet function and of their role in carbon cycling and methane dynamics in a warming Arctic.

Who’s behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

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Andrew Zinin

Master’s in physics with research experience. Long-time science news enthusiast. Plays key role in Science X’s editorial success.

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