Dataset Information

Increases in temperature and nutrient availability positively affect methane-cycling microorganisms in Arctic thermokarst lake sediments.

ABSTRACT: Arctic permafrost soils store large amounts of organic matter that is sensitive to temperature increases and subsequent microbial degradation to methane (CH ₄ ) and carbon dioxide (CO ₂ ). Here, we studied methanogenic and methanotrophic activity and community composition in thermokarst lake sediments from Utqiag?vik (formerly Barrow), Alaska. This experiment was carried out under in situ temperature conditions (4°C) and the IPCC 2013 Arctic climate change scenario (10°C) after addition of methanogenic and methanotrophic substrates for nearly a year. Trimethylamine (TMA) amendment with warming showed highest maximum CH ₄ production rates, being 30% higher at 10°C than at 4°C. Maximum methanotrophic rates increased by up to 57% at 10°C compared to 4°C. 16S rRNA gene sequencing indicated high relative abundance of Methanosarcinaceae in TMA amended incubations, and for methanotrophic incubations Methylococcaeae were highly enriched. Anaerobic methanotrophic activity with nitrite or nitrate as electron acceptor was not detected. This study indicates that the methane cycling microbial community can adapt to temperature increases and that their activity is highly dependent on substrate availability.

SUBMITTER: de Jong AEE

PROVIDER: S-EPMC6334529 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Increases in temperature and nutrient availability positively affect methane-cycling microorganisms in Arctic thermokarst lake sediments.

de Jong Anniek E E AEE In 't Zandt Michiel H MH Meisel Ove H OH Jetten Mike S M MSM Dean Joshua F JF Rasigraf Olivia O Welte Cornelia U CU

Environmental microbiology 20180912 12

Arctic permafrost soils store large amounts of organic matter that is sensitive to temperature increases and subsequent microbial degradation to methane (CH <sub>4</sub> ) and carbon dioxide (CO <sub>2</sub> ). Here, we studied methanogenic and methanotrophic activity and community composition in thermokarst lake sediments from Utqiag˙vik (formerly Barrow), Alaska. This experiment was carried out under in situ temperature conditions (4°C) and the IPCC 2013 Arctic climate change scenario (10°C) a ...[more]

PMID: 29968310

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Project description:Methanotrophs are of major importance in limiting methane emissions from lakes. They are known to preferably inhabit the oxycline of stratified water columns, often assumed due to an intolerance to atmospheric oxygen concentrations, but little is known on the response of methanotrophs to different oxygen concentrations as well as their preference for different electron acceptors. In this study, we enriched a methanotroph of the Methylobacter genus from the oxycline and the anoxic water column of a stratified lake, which was also present in the oxic water column in the winter. We tested the response of this Methylobacter-dominated enrichment culture to different electron acceptors, i.e., oxygen, nitrate, sulfate, and humic substances, and found that, in contrast to earlier results with water column incubations, oxygen was the preferred electron acceptor, leading to methane oxidation rates of 45-72 pmol cell-1 day-1. Despite the general assumption of methanotrophs preferring microaerobic conditions, methane oxidation was most efficient under high oxygen concentrations (>600 μM). Low (<30 μM) oxygen concentrations still supported methane oxidation, but no methane oxidation was observed with trace oxygen concentrations (<9 μM) or under anoxic conditions. Remarkably, the presence of nitrate stimulated methane oxidation rates under oxic conditions, raising the methane oxidation rates by 50% when compared to oxic incubations with ammonium. Under anoxic conditions, no net methane consumption was observed; however, methanotroph abundances were two to three times higher in incubations with nitrate and sulfate compared to anoxic incubations with ammonium as the nitrogen source. Metagenomic sequencing revealed the absence of a complete denitrification pathway in the dominant methanotroph Methylobacter, but the most abundant methylotroph Methylotenera seemed capable of denitrification, which can possibly play a role in the enhanced methane oxidation rates under nitrate-rich conditions.

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Dataset Information

Increases in temperature and nutrient availability positively affect methane-cycling microorganisms in Arctic thermokarst lake sediments.

Publications

Increases in temperature and nutrient availability positively affect methane-cycling microorganisms in Arctic thermokarst lake sediments.

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