Biogeochemical evidence of anaerobic methane oxidation and anaerobic ammonium oxidation in a stratified lake using stable isotopes

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dc.contributor.authorEinsiedl, Florian
dc.contributor.authorWunderlich, Anja
dc.contributor.authorSebilo, Mathieu
dc.contributor.authorCoskun, Ömer K.
dc.contributor.authorOrsi, William D.
dc.contributor.authorMayer, Bernhard
dc.date.accessioned2022-09-02T22:30:39Z
dc.date.available2022-09-02T22:30:39Z
dc.date.issued2020-10-23
dc.description.abstractNitrate pollution of freshwaters and methane emissions into the atmosphere are crucial factors in deteriorating the quality of drinking water and in contributing to global climate change. The n-damo (nitrite-dependent anaerobic methane oxidation), nitrate-dependent anaerobic methane oxidation and the anaerobic oxidation of ammonium (anammox) represent two microbially mediated processes that can reduce nitrogen loading of aquatic ecosystems and associated methane emissions to the atmosphere. Here, we report vertical concentration and stable-isotope profiles of CH4, NO−3, NO−2, and NH+4 in the water column of Fohnsee (lake in southern Bavaria, Germany) that may indicate linkages between denitrification, anaerobic oxidation of methane (AOM), and anammox. At a water depth from 12 to 20 m, a methane–nitrate transition zone (NMTZ) was observed, where δ13C values of methane and δ15N and δ18O of dissolved nitrate markedly increased in concert with decreasing concentrations of methane and nitrate. These data patterns, together with the results of a simple 1-D diffusion model linked with a degradation term, show that the nonlinear methane concentration profile cannot be explained by diffusion and that microbial oxidation of methane coupled with denitrification under anaerobic conditions is the most parsimonious explanation for these data trends. In the methane zone at the bottom of the NMTZ (20 to 22 m) δ15N of ammonium increased by 4 ‰, while ammonium concentrations decreased. In addition, a strong 15N enrichment of dissolved nitrate was observed at a water depth of 20 m, suggesting that anammox is occurring together with denitrification. The conversion of nitrite to N2 and nitrate during anammox is associated with an inverse N isotope fractionation and may explain the observed increasing offset (Δδ15N) of 26 ‰ between δ15N values of dissolved nitrate and nitrite at a water depth of 20 m compared to the Δδ15Nnitrate-nitrite of 11 ‰ obtained in the NMTZ at a water depth between 16 and 18 m. The associated methane concentration and stable-isotope profiles indicate that some of the denitrification may be coupled to AOM, an observation supported by an increased concentration of bacteria known to be involved in n-damo/denitrification with AOM (NC10 and Crenothrix) and anammox (“Candidatus Anammoximicrobium”) whose concentrations were highest in the methane and ammonium oxidation zones, respectively. This study shows the potential for a coupling of microbially mediated nitrate-dependent methane oxidation with anammox in stratified freshwater ecosystems, which may be important for affecting both methane emissions and nitrogen concentrations in lakes.en_US
dc.description.grantingagencyNatural Sciences and Engineering Research Council (NSERC)en_US
dc.description.grantingagencyOtheren_US
dc.identifier.citationEinsiedl, F., Wunderlich, A., Sebilo, M., Coskun, Ö. K., Orsi, W. D., & Mayer, B. (2020). Biogeochemical evidence of anaerobic methane oxidation and anaerobic ammonium oxidation in a stratified lake using stable isotopes. Biogeosciences, 17(20), 5149–5161. https://doi.org/10.5194/bg-17-5149-2020en_US
dc.identifier.doihttps://doi.org/10.5194/bg-17-5149-2020en_US
dc.identifier.grantnumbergrant no. EI 401/10-1en_US
dc.identifier.issn1726-4170
dc.identifier.urihttp://hdl.handle.net/1880/115163
dc.language.isoengen_US
dc.publisherCopernicus Publicationsen_US
dc.publisher.departmentGeoscienceen_US
dc.publisher.facultyScienceen_US
dc.publisher.hasversionpublishedVersionen_US
dc.publisher.institutionUniversity of Calgaryen_US
dc.publisher.policyhttps://www.biogeosciences.net/policies/licence_and_copyright.htmlen_US
dc.rightsUnless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.en_US
dc.rights.urihttps://creativecommons.org/licenses/by/4.0en_US
dc.subjectAnalysisen_US
dc.subjectDenitrificationen_US
dc.subjectDrinking wateren_US
dc.subjectGlobal temperature changesen_US
dc.subjectLife Sciencesen_US
dc.subjectMethaneen_US
dc.subjectNitrogen dioxideen_US
dc.subjectOxidation-reduction reactionen_US
dc.titleBiogeochemical evidence of anaerobic methane oxidation and anaerobic ammonium oxidation in a stratified lake using stable isotopesen_US
dc.typejournal articleen_US
ucalgary.item.requestcopyfalseen_US
ucalgary.scholar.levelFacultyen_US
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