micronutrients; isotopes; sensors; oxidation; methanotrophs; copper; iron; lake; Nano SIMS
Oswald Kirsten, Jegge Corinne, Tischer Jana, Berg Jasmin, Brand Andreas, Miracle Maria, Soria Xavier, Vicente Eduarado, Lehmann Moritz, Zopfi J, Schubert Carsten (2016), Methanotrophy under versatile conditions in the water column of the ferruginous meromictic Lake La Cruz (Spain), in Frontiers in Microbiology
, 7(1762), 1-16.
Oswald Kirsten, Milucka Jana, Brand Andreas, Hach Philipp, Littmann Sten, Wehrli Bernhard, Kuypers Marcel, Schubert Carsten (2016), Variable mehanotrophy at the oxycline and in the anoxic waters of a meromictic lake, in Limnology and Oceanography
, 61, S101-S118.
Brand Andreas, Bruderer Hanna, Oswald Kirsten, Schubert Carsten, Wehrli Bernhard, Guggenheim Carole (2016), Oxygen primay production below the oxycline and its importance for redox dynamics, in Aquatic Sciences
Oswald Kirsten, Milucka Jana, Brand Andreas, Wehrli Bernhard, Kuypers Marcel, Schubert Carsten (2015), Light-dependent aerobic methane oxidation reduces methane emissions from seasonally stratified lakes., in PLOS ONE
, 10(7), e0132574.
Zigah Prosper, Oswald Kirsten, Brand Andreas, Dinkel Christian, Wehrli Bernhard, Schubert Carsten (2015), Molecular and isotopic insights into methane oxidation and associated methanotrophic communities in the water column of a tropical lake (Lake Kivu)., in Limnology and Oceanography
, 60, 553-572.
Oswald Kirsten, Graf Jon, Littmann Sten, Tienken Daniela, Brand Andreas, Wehrli Bernhard, Abertsen Mads, Daims Holger, Wagner Michael, Crenotrhix are major methane consumers in stratified lakes, in The ISME Journal
Brand Andreas, Bruderer Hanna, Oswald Kirsten, Schubert Carsten, Wehrli Bernhard, Guggenheim Carole, Oxygen primay production below the oxycline and its importance for redox cycling, in Aquatic Sciences
Methane emissions from lakes and reservoirs to the atmosphere could contribute up to 8% to the atmospheric flux and should be included in the global CH4 budget. Emission rates from freshwater systems are poorly constrained be-cause methane is produced at highly variable rates, it can be oxidized in the sediment and in the water column, and transferred to the atmosphere either by diffusion or by rising bubbles.Methanotrophic bacteria prefer O2 as an electron acceptor, but several new pathways of methane oxidation in the absence of oxygen have been recently discovered: Microbial methane oxidation can also proceed via reduction of nitrate, nitrite, iron- and manganese oxides. The anaerobic methane oxidation pathway via sulfate reduction has been firmly established for marine systems. The new, alternative pathways could stabilize methane oxidation rates under fluctuating oxygen conditions at redox boundaries in lakes. They could also extend the depth interval in which methane oxidation is occurring when oxygen disappears in stratified lakes or at the sediment-water interface. The factors governing methane oxidation pathways under natural conditions are to a large extend unknown, because most evidence for alternative electron acceptors is based on laboratory incubations. One of the potential controlling factors for methanotrophic communities has been studied extensively under controlled conditions: The two different enzymes for the oxidation of CH4 with O2 need copper and iron as micro-nutrients. The availability of these trace metals in the critical zone could therefore trigger changes in the oxidation pathways but has not yet been systematically investigated under natural conditions.The ongoing project provided new insights into the role of oxygenic phototrophs and the manganese cycle for methane oxidation. With this proposed 2-year continuation we will address the following research questions:•Which pathways of methane oxidation are operating at different redox environments in lakes and which fraction of methane is transformed by different electron acceptors?•Which factors such as the concentrations and fluxes of methane, electron acceptors and micronutrients are governing the oxidation pathways of methane?•What are the consequences of coupled redox cascades such as oxygenic phototrophs or the manganese redox cycle for the overall methane oxidation, its isotopic signature and for dark microbial production?We propose to extend our ongoing field studies in five stratified lakes in Switzerland, Spain, Central Africa and West-ern Canada with contrasting boundary conditions. They differ in the availability of methane and electron acceptors, the vertical mixing regime and the seasonality of redox cycling. Our biogeochemical analysis combines our expertise in high-resolution profiling and sampling techniques, the analysis of stable isotopes and in-situ reaction rates, and the know-how in reaction-transport modeling of the water column in physically well-characterized lake systems. By focusing on consistent biogeochemical analysis of methane oxidation across several systems the project aims at providing general insights and reference data for improved global estimates.