Dataset Information

Microbial nitrogen fixation and methane oxidation are strongly enhanced by light in Sphagnum mosses.

ABSTRACT: Peatlands have acted as C-sinks for millennia, storing large amounts of carbon, of which a significant amount is yearly released as methane (CH₄). Sphagnum mosses are a key genus in many peat ecosystems and these mosses live in close association with methane-oxidizing and nitrogen-fixing microorganisms. To disentangle mechanisms which may control Sphagnum-associated methane-oxidation and nitrogen-fixation, we applied four treatments to Sphagnum mosses from a pristine peatland in Finland: nitrogen fertilization, phosphorus fertilization, CH₄ addition and light. N and P fertilization resulted in nutrient accumulation in the moss tissue, but did not increase Sphagnum growth. While net CO₂ fixation rates remained unaffected in the N and P treatment, net CH₄ emissions decreased because of enhanced CH₄ oxidation. CH₄ addition did not affect Sphagnum performance in the present set-up. Light, however, clearly stimulated the activity of associated nitrogen-fixing and methane-oxidizing microorganisms, increasing N₂ fixation rates threefold and CH₄ oxidation rates fivefold. This underlines the strong connection between Sphagnum and associated N₂ fixation and CH₄ oxidation. It furthermore indicates that phototrophy is a strong control of microbial activity, which can be directly or indirectly.

SUBMITTER: Kox MAR

PROVIDER: S-EPMC7109220 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Microbial nitrogen fixation and methane oxidation are strongly enhanced by light in Sphagnum mosses.

Kox Martine A R MAR van den Elzen Eva E Lamers Leon P M LPM Jetten Mike S M MSM van Kessel Maartje A H J MAHJ

AMB Express 20200331 1

Peatlands have acted as C-sinks for millennia, storing large amounts of carbon, of which a significant amount is yearly released as methane (CH<sub>4</sub>). Sphagnum mosses are a key genus in many peat ecosystems and these mosses live in close association with methane-oxidizing and nitrogen-fixing microorganisms. To disentangle mechanisms which may control Sphagnum-associated methane-oxidation and nitrogen-fixation, we applied four treatments to Sphagnum mosses from a pristine peatland in Finla ...[more]

PMID: 32236738

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Project description:Peat forming Sphagnum mosses are able to prevent the dominance of vascular plants under ombrotrophic conditions by efficiently scavenging atmospherically deposited nitrogen (N). N-uptake kinetics of these mosses are therefore expected to play a key role in differential N availability, plant competition, and carbon sequestration in Sphagnum peatlands. The interacting effects of rain N concentration and exposure time on moss N-uptake rates are, however, poorly understood. We investigated the effects of N-concentration (1, 5, 10, 50, 100, 500 µM), N-form ((15)N-ammonium or nitrate) and exposure time (0.5, 2, 72 h) on uptake kinetics for Sphagnum magellanicum from a pristine bog in Patagonia (Argentina) and from a Dutch bog exposed to decades of N-pollution. Uptake rates for ammonium were higher than for nitrate, and N-binding at adsorption sites was negligible. During the first 0.5 h, N-uptake followed saturation kinetics revealing a high affinity (Km 3.5-6.5 µM). Ammonium was taken up 8 times faster than nitrate, whereas over 72 hours this was only 2 times. Uptake rates decreased drastically with increasing exposure times, which implies that many short-term N-uptake experiments in literature may well have overestimated long-term uptake rates and ecosystem retention. Sphagnum from the polluted site (i.e. long-term N exposure) showed lower uptake rates than mosses from the pristine site, indicating an adaptive response. Sphagnum therefore appears to be highly efficient in using short N pulses (e.g. rainfall in pristine areas). This strategy has important ecological and evolutionary implications: at high N input rates, the risk of N-toxicity seems to be reduced by lower uptake rates of Sphagnum, at the expense of its long-term filter capacity and related competitive advantage over vascular plants. As shown by our conceptual model, interacting effects of N-deposition and climate change (changes in rainfall) will seriously alter the functioning of Sphagnum peatlands.

Dataset Information

Microbial nitrogen fixation and methane oxidation are strongly enhanced by light in Sphagnum mosses.

Publications

Microbial nitrogen fixation and methane oxidation are strongly enhanced by light in Sphagnum mosses.

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