Temperature differently affected methanogenic pathways and microbial communities in sub-Antarctic freshwater ecosystems
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2021Metadata
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Lavergne, Céline
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Temperature differently affected methanogenic pathways and microbial communities in sub-Antarctic freshwater ecosystems
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Abstract
Freshwater ecosystems are responsible for an important part of the methane (CH4) emissions which are likely to
change with global warming. This study aims to evaluate temperature-induced (from 5 to 20 ◦C) changes on
microbial community structure and methanogenic pathways in five sub-Antarctic lake sediments from Magallanes
strait to Cape Horn, Chile. We combined in situ CH4 flux measurements, CH4 production rates (MPRs),
gene abundance quantification and microbial community structure analysis (metabarcoding of the 16S rRNA
gene). Under unamended conditions, a temperature increase of 5 ◦C doubled MPR while microbial community
structure was not affected. Stimulation of methanogenesis by methanogenic precursors as acetate and H2/CO2,
resulted in an increase of MPRs up to 127-fold and 19-fold, respectively, as well as an enrichment of mcrAcarriers
strikingly stronger under acetate amendment. At low temperatures, H2/CO2-derived MPRs were
considerably lower (down to 160-fold lower) than the acetate-derived MPRs, but the contribution of hydrogenotrophic
methanogenesis increased with temperature. Temperature dependence of MPRs was significantly
higher in incubations spiked with H2/CO2 (c. 1.9 eV) compared to incubations spiked with acetate or unamended
(c. 0.8 eV). Temperature was not found to shape the total microbial community structure, that rather exhibited a
site-specific variability among the studied lakes. However, the methanogenic archaeal community structure was
driven by amended methanogenic precursors with a dominance of Methanobacterium in H2/CO2-based incubations
and Methanosarcina in acetate-based incubations. We also suggested the importance of acetogenic H2-
production outcompeting hydrogenotrohic methanogenesis especially at low temperatures, further supported by
homoacetogen proportion in the microcosm communities. The combination of in situ-, and laboratory-based
measurements and molecular approaches indicates that the hydrogenotrophic pathway may become more
important with increasing temperatures than the acetoclastic pathway. In a continuously warming environment
driven by climate change, such issues are crucial and may receive more attention.
Patrocinador
French ministries MAEDI (Ministere des Affaires Etrangeres et du Developpement International)
MENESR (Ministere de lEducation nationale, de l'Enseignement superieur et de la Recherche)
Chilean CONICYT (Comision Nacional de Investigacion Cientifica y Tecnologica) ELAC2014_DCC-0092
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Environment International 154 (2021) 106575
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