Abstract

Eutrophication increases the input of labile, algae-derived, organic matter (OM) into lake sediments. This potentially increases methane (CH4) emissions from sediment to water through increased methane production rates and decreased methane oxidation efficiencyefficiency in sediments. However, the effecteffect of OM lability on the structure of methane oxidizing (methanotrophic) and methane producing (methanogenic) microbial communities in lake sediments is still understudied. We studied the vertical profilesprofiles of the sediment and porewater geochemistry and the microbial communities (16S rRNA gene amplicon sequencing) at fivefive profundal stations of an oligo-mesotrophic, boreal lake (Lake Paajarvi, Finland), varying in surface sediment OM sources (assessed via sediment C:N ratio). Porewater profilesprofiles of methane, dissolved inorganic carbon (DIC), acetate, iron, and sulfur suggested that sites with more autochthonous OM showed higher overall OM lability, which increased remineralization rates, leading to increased electron acceptor (EA) consumption and methane emissions from sediment to water. When OM lability increased, the abundance of anaerobic nitrite-reducing methanotrophs (Candidatus Methylomirabilis) relative to aerobic methanotrophs (Methylococcales) in the methane oxidation layer of sediment surface decreased, suggesting that Methylococcales were more competitive than Ca. Methylomirabilis under decreasing redox conditions and increasing methane availability due to their more diverse metabolism (fermentation and anaerobic respiration) and lower affinityaffinity for methane. Furthermore, when OM lability increased, the abundance of methanotrophic community in the sediment surface layer, especially Ca. Methylomirabilis, relative to the methanogenic community decreased. We conclude that increasing input of labile OM, subsequently affectingaffecting the redox zonation of sediments, significantlysignificantly modifies the methane producing and consuming microbial community of lake sediments.

Keywords

greenhouse gas; freshwater; methanotroph; methanogen; 16S rRNA gene; eutrophication

Published in

Microbiology Spectrum
2023, Volume: 11, number: 5, article number: e0195523
Publisher: AMER SOC MICROBIOLOGY

SLU Authors

• Peura, Sari

  • Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Geochemistry
Microbiology


Publication Identifiers

DOI: https://doi.org/10.1128/spectrum.01955-23

Permanent link to this page (URI)

https://res.slu.se/id/publ/126599