Microbial diversity and activity in the active layer of thawing permafrost: a case study in Northern Norway
Quabron, Gilles
Promotor(s) : Joaquim-Justo, Célia ; Lee, Hanna
Date of defense : 3-Sep-2018 • Permalink : http://hdl.handle.net/2268.2/6023
Details
Title : | Microbial diversity and activity in the active layer of thawing permafrost: a case study in Northern Norway |
Author : | Quabron, Gilles |
Date of defense : | 3-Sep-2018 |
Advisor(s) : | Joaquim-Justo, Célia
Lee, Hanna |
Committee's member(s) : | Romain, Anne-Claude
Falzone, Claudia |
Language : | English |
Number of pages : | 76 |
Keywords : | [en] permafrost thaw [en] microbial diversity [en] microbial activity [en] palsa [en] 16s rRNA [en] qPCR [en] mcrA [en] pmoA [en] Biolog [en] beta-glucosidase [en] climate change [en] Norway |
Discipline(s) : | Life sciences > Microbiology |
Research unit : | Uni Research Climate |
Target public : | Researchers Student |
Institution(s) : | Université de Liège, Liège, Belgique |
Degree: | Master en sciences et gestion de l'environnement, à finalité spécialisée en surveillance de l'environnement |
Faculty: | Master thesis of the Faculté des Sciences |
Abstract
[en] Permafrost environments, which store large quantities of soil organic carbon, are threatened by climate change-induced thaw that would render frozen organic matter bioavailable for microorganisms leading to an increase in greenhouse gases emissions. Hence understanding the response of permafrost microbial communities to thawing is necessary to evaluate the permafrost carbon feedback to global change. Microbial diversity and activity were studied across two thaw stages (intact and degrading permafrost) at different depths in a palsa found in Northern Norway. This study investigated soil microbial community composition by Illumina Miseq sequencing of the 16S rRNA gene while bacterial, archaeal, methanogens and methanotrophs abundance was assessed by qPCR. Microbial heterotrophic activity was evaluated using enzymatic and functional metabolic assays. Microbial communities’ composition and activity were found to differ between the two thaw stages. The intact palsa (IP) presented high richness that decreased with depth while the degrading palsa (DP) exhibited less species-rich communities across depth. Relative abundance of members of the phylum Proteobacteria known to thrive in higher carbon and nutrient availability increased in the DP while members of the phylum AD3, which dominated the deepest part of the IP, almost disappeared in the DP. Bacterial, archaeal, methanogens and methanotrophs were more abundant in the thawing permafrost than in the intact palsa. The DP exhibited high and similar microbial biomass across depths while the IP showed high microbial abundance only in the topsoil layer. In addition, populations of methane-producing microorganisms were found to be strongly positively correlated to methane oxidizers abundance, suggesting a close spatial relationship between these two communities. Heterotrophic prokaryotes found in the DP displayed higher enzymatic and functional metabolic activity across depth than in the IP. Collectively, these results suggest a shift in microbial prokaryotic communities as a result of permafrost thaw characterized by less species-rich populations, by an increasing biomass of greenhouse gases-related microorganisms as well as a higher microbial activity across depth, potentially leading to greater greenhouse gases emissions that would exacerbate the positive feedbacks from permafrost carbon to climate.
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