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Variable mehanotrophy at the oxycline and in the anoxic waters of a meromictic lake

Publikationsart Peer-reviewed
Publikationsform Originalbeitrag (peer-reviewed)
Autor/in Oswald Kirsten, Milucka Jana, Brand Andreas, Hach Philipp, Littmann Sten, Wehrli Bernhard, Kuypers Marcel, Schubert Carsten,
Projekt Factors governing methane oxidation pathways at redox boundaries in lakes
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Originalbeitrag (peer-reviewed)

Zeitschrift Limnology and Oceanography
Volume (Issue) 61
Seite(n) S101 - S118
Titel der Proceedings Limnology and Oceanography
DOI 10.1002/lno.10312

Open Access

Abstract

Freshwater lakes represent a substantial natural source of methane to the atmosphere and thus contribute to global climate change. Microbial methane oxidation is an important control on methane release from these systems, where oxygen appears to be the most essential electron acceptor for this process. However, there is extensive geochemical evidence that methane is also oxidized under anoxic conditions in lakes, though the details about the exact mechanism have still not been resolved. We investigated methane oxidation pathways in the water column of the meromictic Lake Zug and provide evidence for ongoing methane cycling. Methane oxidation is mediated by aerobic methane-oxidizing bacteria at the oxic/anoxic boundary and also in the anoxic hypolimnion. Gammaproteobacterial methanotrophs constituted the most abundant methanotrophic group by far and were active under all investigated conditions – oxic, sub-oxic and anoxic. These methane-oxidizing bacteria utilized oxygen but also grew under strictly anoxic conditions with supplemented iron- or manganese oxide. These findings indicate that gammaproteobacterial methanotrophs in Lake Zug could be facultative anaerobes, able to switch to other electron acceptors when oxygen is not available. Previous studies have speculated that aerobic methanotrophs found in anoxic lake water are sustained by a periodic supply of oxygen. Here we present novel evidence suggesting that an unknown metabolic pathway could be responsible for methane removal in limnic systems when oxygen is absent.
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