Methane dynamics regulated by microbial community response to permafrost thaw

• Published in: Nature (London) Vol. 514; no. 7523; pp. 478 - 481
• Main Authors: McCalley, Carmody K., Woodcroft, Ben J., Hodgkins, Suzanne B., Wehr, Richard A., Kim, Eun-Hae, Mondav, Rhiannon, Crill, Patrick M., Chanton, Jeffrey P., Rich, Virginia I., Tyson, Gene W., Saleska, Scott R.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23-10-2014; Nature Publishing Group
• Subjects: 140/125; 140/58; 45/23; 704/106/47; 704/158/2466; 704/158/47; 704/158/855; Anaerobiosis; Arctic Regions; Atmosphere - chemistry; Biogeochemistry; Biologi med inriktning mot mikrobiologi; Biology with specialization in Microbiology; Carbon cycle (Biogeochemistry); Carbon dioxide; Carbon Dioxide - metabolism; Carbon dioxide emissions; climate change; Community composition; Ecosystem; Ecosystems; Emissions; Environment; Environmental aspects; ENVIRONMENTAL SCIENCES; Freezing; Frozen ground; Greenhouse gases; Humanities and Social Sciences; Isotopes; letter; Methane; Methane - analysis; Methane - metabolism; Methanogenesis; Microbial activity; Microbial ecology; Microorganisms; multidisciplinary; Permafrost; Science; Soil Microbiology; Stable isotope analysis; stable isotopes; Studies; Sweden; Thawing; Wetlands; Arctic Regions; Sweden
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature13798

The abundance of key microbial lineages can be used to predict atmospherically relevant patterns in methane isotopes and the proportion of carbon metabolized to methane during permafrost thaw, suggesting that microbial ecology may be important in ecosystem-scale responses to global change.
Microbial influence on permafrost methane release
Thawing of permafrost — the frozen subsoil found in arctic and sub-arctic regions — is seen as a potential cause of soil carbon loss with accompanying emissions of the greenhouse gases methane and carbon dioxide. Carmody McCalley
et al
. use a natural landscape gradient of permafrost thaw in northern Sweden as a model to investigate the role of microbial communities in regulating methane cycling. They show that the abundance of key microbial lineages can be used to predict atmospherically relevant patterns in methane isotopes and the proportion of carbon metabolized to methane during permafrost thaw, suggesting that microbial ecology can play an important role in the ecosystem-scale responses to global change.
Permafrost contains about 50% of the global soil carbon
1
. It is thought that the thawing of permafrost can lead to a loss of soil carbon in the form of methane and carbon dioxide emissions
2
,
3
. The magnitude of the resulting positive climate feedback of such greenhouse gas emissions is still unknown
3
and may to a large extent depend on the poorly understood role of microbial community composition in regulating the metabolic processes that drive such ecosystem-scale greenhouse gas fluxes. Here we show that changes in vegetation and increasing methane emissions with permafrost thaw are associated with a switch from hydrogenotrophic to partly acetoclastic methanogenesis, resulting in a large shift in the δ
13
C signature (10–15‰) of emitted methane. We used a natural landscape gradient of permafrost thaw in northern Sweden
4
,
5
as a model to investigate the role of microbial communities in regulating methane cycling, and to test whether a knowledge of community dynamics could improve predictions of carbon emissions under loss of permafrost. Abundance of the methanogen Candidatus ‘
Methanoflorens stordalenmirensis
’
6
is a key predictor of the shifts in methane isotopes, which in turn predicts the proportions of carbon emitted as methane and as carbon dioxide, an important factor for simulating the climate feedback associated with permafrost thaw in global models
3
,
7
. By showing that the abundance of key microbial lineages can be used to predict atmospherically relevant patterns in methane isotopes and the proportion of carbon metabolized to methane during permafrost thaw, we establish a basis for scaling changing microbial communities to ecosystem isotope dynamics. Our findings indicate that microbial ecology may be important in ecosystem-scale responses to global change.