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Methane oxidation coupled to oxygenic photosynthesis in anoxic waters

Methane oxidation coupled to oxygenic photosynthesis in anoxic waters
Methane oxidation coupled to oxygenic photosynthesis in anoxic waters

Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atmosphere. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addition of oxygen enhanced the rates of methane oxidation. An equally pronounced stimulation was also observed when the anoxic water samples were incubated in the light. Our combined results from molecular, biogeochemical and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidation of methane fuelled by in situ oxygen production by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidation coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes.
1751-7362
1991-2002
Milucka, Jana
00bdb9e4-84f7-480f-95da-80de84ad4493
Kirf, Mathias
70928af4-a2aa-4f2f-8cc6-06b3fe6e44cd
Lu, Lu
58518fe5-835d-417b-98ec-e44f1b52c08e
Krupke, Andreas
a90d7c63-8707-407d-a5e3-3289ff2a4f80
Lam, Phyllis
996aef80-a15d-4827-aed8-1b97b378f6ad
Littmann, Sten
5430fff4-6d58-4fa2-9af4-3f48cce399c0
Kuypers, Marcel M.M.
b6288cfb-42bc-469c-93fe-8fbb40d97bec
Schubert, Carsten J.
3a342804-da96-4f3e-9333-fc054303002d
Milucka, Jana
00bdb9e4-84f7-480f-95da-80de84ad4493
Kirf, Mathias
70928af4-a2aa-4f2f-8cc6-06b3fe6e44cd
Lu, Lu
58518fe5-835d-417b-98ec-e44f1b52c08e
Krupke, Andreas
a90d7c63-8707-407d-a5e3-3289ff2a4f80
Lam, Phyllis
996aef80-a15d-4827-aed8-1b97b378f6ad
Littmann, Sten
5430fff4-6d58-4fa2-9af4-3f48cce399c0
Kuypers, Marcel M.M.
b6288cfb-42bc-469c-93fe-8fbb40d97bec
Schubert, Carsten J.
3a342804-da96-4f3e-9333-fc054303002d

Milucka, Jana, Kirf, Mathias, Lu, Lu, Krupke, Andreas, Lam, Phyllis, Littmann, Sten, Kuypers, Marcel M.M. and Schubert, Carsten J. (2015) Methane oxidation coupled to oxygenic photosynthesis in anoxic waters. The ISME Journal, 9, 1991-2002. (doi:10.1038/ismej.2015.12).

Record type: Article

Abstract


Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atmosphere. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addition of oxygen enhanced the rates of methane oxidation. An equally pronounced stimulation was also observed when the anoxic water samples were incubated in the light. Our combined results from molecular, biogeochemical and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidation of methane fuelled by in situ oxygen production by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidation coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes.

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More information

Accepted/In Press date: 19 December 2014
e-pub ahead of print date: 13 February 2015
Published date: 2015
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 374609
URI: http://eprints.soton.ac.uk/id/eprint/374609
ISSN: 1751-7362
PURE UUID: d8cb005e-ae95-4f76-81a2-2ceb7d5d1968
ORCID for Phyllis Lam: ORCID iD orcid.org/0000-0003-2067-171X

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Date deposited: 23 Feb 2015 17:21
Last modified: 09 Jan 2022 03:44

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Contributors

Author: Jana Milucka
Author: Mathias Kirf
Author: Lu Lu
Author: Andreas Krupke
Author: Phyllis Lam ORCID iD
Author: Sten Littmann
Author: Marcel M.M. Kuypers
Author: Carsten J. Schubert

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