methane oxidation; methanotrophs; chemical sensors; stable isotopes; methane; oxidation; lake; stable isotope; biomarker; profiling
Oswald Kirsten, Graf Jon S., Littmann Sten, Tienken Daniela, Brand Andreas, Wehrli Bernhard, Albertsen Mads, Daims Holger, Wagner Michael, Kuypers Marcel M.M., Schubert Carsten J., Miluka Jana (2017), Crenothrix are major methane consumers in stratified lakes, in ISME Journal
Oswald Kirsten, Milucka Jana, Brand Andreas, Hach Philipp, Littmann Sten, Wehrli Bernhard, Kuypers Marcel M. M., Schubert Carsten J. (2016), Aerobic gammaproteobacterial methanotrophs mitigate methane emissions from oxic and anoxic lake waters, in LIMNOLOGY AND OCEANOGRAPHY
, 61, 101-118.
Oswald Kirsten, Jegge Corinne, Tischer Jana, Berg Jasmine, Brand Andreas, Miracle Maria R., Soria Xavier, Vicente Eduardo, Lehmann Moritz F., Zopfi Jakob, Schubert Carsten J. (2016), Methanotrophy under Versatile Conditions in the Water Column of the Ferruginous Meromictic Lake La Cruz (Spain), in FRONTIERS IN MICROBIOLOGY
, 7, 1-16.
Brand Andreas, Bruderer Hannah, Oswald Kirsten, Guggenheim Carole, Schubert Carsten J., Wehrli Bernhard (2016), Oxygenic primary production below the oxycline and its importance for redox dynamics, in AQUATIC SCIENCES
, 78(4), 727-741.
Oswald Kirsten, Milucka Jana, Brand Andreas, Littmann Sten, Wehrli Bernhard, Kuypers Marcel M. M., Schubert Carsten J. (2015), Light-Dependent Aerobic Methane Oxidation Reduces Methane Emissions from Seasonally Stratified Lakes., in PLOS one
, 10(7), 1-22.
Zigah Prosper K., Oswald Kirsten, Brand Andreas, Dinkel Christian, Wehrli Bernhard, Schubert Carsten J. (2015), Methane oxidation pathways and associated methanotrophic communities in the water column of a tropical lake, in LIMNOLOGY AND OCEANOGRAPHY
, 60(2), 553-572.
Recent reviews indicate that methane emissions from lakes and reservoirs to the atmosphere should be included in global budget. Natural wetlands contribute 20-33% of the total emissions. Lakes and reservoirs have so far not been part of global budgets but they could contribute up to 10% to the atmospheric flux. Such estimates are poorly constrained because methane is produced at highly variable rates in anoxic freshwater sediments, it can be oxidized in the sediment and in the water column, and transferred to the atmosphere either by diffusion or by bubble transport . Over the last years, several pathways of methane oxidation in the absence of oxygen have been established. Anaerobic methane oxidation via sulfate reduction is now firmly established for marine systems. Laboratory evidence further proves that microbial methane oxidation is also proceeding via nitrate, nitrite, and iron and mangenese oxides as electron acceptors. These new pathways could stabilize methane oxidation rates under fluctuating oxygen conditions in freshwater systems where gaps between the oxic zone and deep-water methane have been observed. So far it is not clear, to which extend micronutrients such as copper may limit methane oxidation by oxygen, but the importance of methanotrophic microorganisms for dark carbon fixation and for planktonik food webs is emerging as an important as pect of the carbon cycle in freshwater systems.Here we propose to address the following research questions•Which pathways of methane oxidation are operating at contrasting redox environments of lakes and which fraction of methane is transformed by different electron acceptors?•How are the concentrations and the fluxes of methane, electron acceptors and micronutrients like copper controlling oxidation pathways and their rates?•What are the consequences of such coupled redox cascades for the overall methane oxidation, for the isotopic signature of methane, and for dark microbial production?We will address these question with four selected field studies in Switzerland, Spain, Central Africa and Western Canada. The lakes to be studied show redox interfaces in the water column with contrasting boundary conditions regarding the availability of methane and electron acceptors, the vertical mixing regime and the seasonality of redox cycling. Our biogeochemical analysis will combine our expertise in•newly established high-resolution profiling and sampling techniques, •the analysis of stable isotopes, biomarkers and in-situ reaction rates and•and the know-how in reaction-transport modeling of the water column in physically well-characterized lake systems.