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Revision des Methankreislaufes in Seen: Quellen und Senken in 2 deutschen Seen unter besonderer Berücksichtigung der Methanakkumulation in sauerstoffhaltigenen Wasserschichten

Fachliche Zuordnung Hydrogeologie, Hydrologie, Limnologie, Siedlungswasserwirtschaft, Wasserchemie, Integrierte Wasserressourcen-Bewirtschaftung
Mikrobielle Ökologie und Angewandte Mikrobiologie
Mineralogie, Petrologie und Geochemie
Förderung Förderung von 2013 bis 2022
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 241479293
 
Erstellungsjahr 2023

Zusammenfassung der Projektergebnisse

In light of the recently discovered methane (CH4 ) accumulation in oxic waters, it is crucial to understand the precise CH4 production mechanisms under varying environmental conditions. This understanding is essential for better estimating its contribution to the global methane budget and reducing uncertainties regarding CH4 sources and sinks. Previously, it was assumed that the magnitude of CH4 accumulation in the water column primarily depended on complex interactions among phytoplankton, methanogenic Archaea, and methanotrophic bacteria. However, the widely reported 'methane paradox' in oceans and lakes, characterized by CH4 oversaturation in the oxygenated mid-water column, challenges the prevailing paradigm of exclusive anoxic methanogenesis via classical methanogenesis. The overall aim of this research was to comprehensively characterize the complete CH4 cycle in two contrasting but common lake types by quantifying the CH4 bulk sources and sinks using a detailed mass balance approach, combined with multiple stable isotope measurements and in situ incubation experiments. Generally, we closely followed the project according to the proposed research plan and most aspects of the work packages were addressed successfully. Our research project provides a comprehensive multi-year dataset of field work investigating sources and sinks of CH4 in the sediment and water column of lakes Stechlin and Willersinnweiher combining concentrations as well as stable carbon (δ13C-CH4 ) and hydrogen (δ2H-CH4 ) values and redox/nutrient status during seasonal variations between 2019 and 2021 as well as laboratory experiments where we identified precursor compounds of oxic methane production (OMP) in both lakes. Furthermore, our project opened up new avenues regarding CH4 formation from cyanobacteria and CH4 formation in the oxic epilimnion of marine and freshwater environments. This work was complemented with measurements of stable carbon isotope signatures and fractionations of CH4 emitted from phytoplankton. In addition, we performed 3-D hydrodynamical modelling to unravel the lateral flux of CH4 emitted from littoral sources (submitted) to obtain an improved certainty of our CH4 mass balance and OMP contribution to CH4 emissions from Lake Stechlin. Most of our results are published in peer-reviewed journals (21 publications in Nature, Nature Communications, Science Advances, L&O, etc., 5 are common publications between the groups, 2 further manuscripts are submitted). Nevertheless, there was work that could not be performed. This was the case with our proposed photosynthesis inhibitor experiments (part of work package 3 D “Role of photosynthesis - inhibitor experiments”). This was mainly due to the corona pandemic leading to logistic problems and time constraints regarding the collection of field samples and the availability of axenic cultures of cyanobacteria and green algae. We hope we can address these issues in the near future.

Projektbezogene Publikationen (Auswahl)

 
 

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