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

• Antragsteller: Professor Dr. Hans-Peter Grossart; Professor Dr. Frank Keppler
• 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

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)

• A Fast-Response Automated Gas Equilibrator (FaRAGE) for continuous in situ measurement of CH4 and CO2 dissolved in water. Hydrology and Earth System Sciences, 24(7), 3871–3880.
  Xiao, Shangbin; Liu, Liu; Wang, Wei; Lorke, Andreas; Woodhouse, Jason & Grossart, Hans-Peter
  
• A fast and sensitive method for the continuous in situ determination of dissolved methane and its δ13C‐isotope ratio in surface waters. Limnology and Oceanography: Methods, 16(5), 273-285.
  Hartmann, Jan F.; Gentz, Torben; Schiller, Amanda; Greule, Markus; Grossart, Hans‐Peter; Ionescu, Danny; Keppler, Frank; Martinez‐Cruz, Karla; Sepulveda‐Jauregui, Armando & Isenbeck‐Schröter, Margot
  
• Contribution of oxic methane production to surface methane emission in lakes and its global importance. Nature Communications, 10(1).
  Günthel, Marco; Donis, Daphne; Kirillin, Georgiy; Ionescu, Danny; Bizic, Mina; McGinnis, Daniel F.; Grossart, Hans-Peter & Tang, Kam W.
  
• Aquatic and terrestrial cyanobacteria produce methane. Science Advances, 6(3).
  Bižić, M.; Klintzsch, T.; Ionescu, D.; Hindiyeh, M. Y.; Günthel, M.; Muro-Pastor, A. M.; Eckert, W.; Urich, T.; Keppler, F. & Grossart, H.-P.
  
• Effects of Temperature and Light on Methane Production of Widespread Marine Phytoplankton. Journal of Geophysical Research: Biogeosciences, 125(9).
  Klintzsch, T.; Langer, G.; Wieland, A.; Geisinger, H.; Lenhart, K.; Nehrke, G. & Keppler, F.
  
• High Spatiotemporal Dynamics of Methane Production and Emission in Oxic Surface Water. Environmental Science & Technology, 54(3), 1451-1463.
  Hartmann, Jan F.; Günthel, Marco; Klintzsch, Thomas; Kirillin, Georgiy; Grossart, Hans-Peter; Keppler, Frank & Isenbeck-Schröter, Margot
  
• Methane Paradox. Encyclopedia of Life Sciences (2020, 2, 17), 1-11. Wiley.
  Bižić, Mina; Grossart, Hans‐Peter & Ionescu, Danny
  
• Photosynthesis‐driven methane production in oxic lake water as an important contributor to methane emission. Limnology and Oceanography, 65(12), 2853-2865.
  Günthel, Marco; Klawonn, Isabell; Woodhouse, Jason; Bižić, Mina; Ionescu, Danny; Ganzert, Lars; Kümmel, Steffen; Nijenhuis, Ivonne; Zoccarato, Luca; Grossart, Hans‐Peter & Tang, Kam W.
  
• Global co‐occurrence of methanogenic archaea and methanotrophic bacteria in Microcystis aggregates. Environmental Microbiology, 23(11), 6503-6519.
  Li, Chuang; Hambright, K. David; Bowen, Hannah G.; Trammell, Majoi A.; Grossart, Hans‐Peter; Burford, Michele A.; Hamilton, David P.; Jiang, Helong; Latour, Delphine; Meyer, Elisabeth I.; Padisák, Judit; Zamor, Richard M. & Krumholz, Lee R.
  
• Reply to ‘Oxic methanogenesis is only a minor source of lake-wide diffusive CH4 emissions from lakes’. Nature Communications, 12(1).
  Günthel, Marco; Donis, Daphne; Kirillin, Georgiy; Ionescu, Danny; Bizic, Mina; McGinnis, Daniel F.; Grossart, Hans-Peter & Tang, Kam W.
  
• The impact of seasonal sulfate–methane transition zones on methane cycling in a sulfate‐enriched freshwater environment. Limnology and Oceanography, 66(6), 2290-2308.
  Kleint, Jan F.; Wellach, Yannic; Schroll, Moritz; Keppler, Frank & Isenbeck‐Schröter, Margot
  
• Application of concentration and 2-dimensional stable isotope measurements of methane to constrain sources and sinks in a seasonally stratified freshwater lake. Frontiers in Environmental Science, 10(2022, 11, 3).
  Einzmann, Teresa; Schroll, Moritz; Kleint, Jan F.; Greule, Markus & Keppler, Frank
  
• Methane formation driven by reactive oxygen species across all living organisms. Nature, 603(7901), 482-487.
  Ernst, Leonard; Steinfeld, Benedikt; Barayeu, Uladzimir; Klintzsch, Thomas; Kurth, Markus; Grimm, Dirk; Dick, Tobias P.; Rebelein, Johannes G.; Bischofs, Ilka B. & Keppler, Frank
  
• Potential role of submerged macrophytes for oxic methane production in aquatic ecosystems. Limnology and Oceanography, 67(S2).
  Hilt, Sabine; Grossart, Hans‐Peter; McGinnis, Daniel F. & Keppler, Frank
  
• Methane accumulation and its potential precursor compounds in the oxic surface water layer of two contrasting stratified lakes. Science of The Total Environment, 903(2023, 12), 166205.
  Schroll, Moritz; Liu, Liu; Einzmann, Teresa; Keppler, Frank & Grossart, Hans-Peter
  
• Stable Carbon Isotope Signature of Methane Released From Phytoplankton. Geophysical Research Letters, 50(12).
  Klintzsch, T.; Geisinger, H.; Wieland, A.; Langer, G.; Nehrke, G.; Bizic, M.; Greule, M.; Lenhart, K.; Borsch, C.; Schroll, M. & Keppler, F.