Revising the methane cycling in lakes: sources and sinks in two German lakes with specific consideration of methane accumulation in oxic waters

Background/Summary

This project is a collaboration of two german research groups tackling the understanding of the formation and degradation processes/mechanisms of methane (CH₄) in the environment and ecological aspects of lake waters to better understand the role of lakes in regional and global CH₄ cycling.

Recently, CH₄ accumulation in oxic waters has been found in freshwater and marine waters worldwide. We could show a close spatio-temporal relationship between the dynamics of alga (e.g. cyanobacteria and cryptophytes) and CH₄ in the oxic water layers of Lake Stechlin. Whilst the recently established methyl phosphonate metabolism might be present in our lakes we found first evidence that algae directly produce CH₄ during photosynthesis. However, the possible mechanism and its contribution to CH₄ produced in oxic waters to total CH₄ fluxes remains largely unknown.

Therefore, the complete CH₄ budget of two lakes in Germany will be quantified in detail, i.e. CH₄ bulk sources and sinks will be evaluated by a detailed mass balance approach combined with in situ incubation experiments. Our contrasting field sites/lakes (oligo-mesotrophic Lake Stechlin and eutrophic Willersinnweiher) represent two main temperate lake types (deep /nutrient-poor and shallow /nutrient-rich) well studied and biogeochemically characterized by the two research institutes. In both lakes, the presence of specific processes of CH₄ production, accumulation and its release to the atmosphere depend on a complicated interplay of physical, chemical and biological factors favoring certain organisms and related processes. Thus our main objectives are to entangle the complicated interplay between environmental variables and processes of CH₄ formation, accumulation and release, and to provide a seasonal CH₄ budget of the lake to determine the relevance of oxic CH₄ formation for regional and global CH₄ cycling.

Conceptual scheme of potential CH₄ sources and sinks in lakes (Figure taken from Tang et al. 2016).

Relevant publications

• Hartmann, J. F., Günthel, M., Klintzsch, T., Kirillin, G., Grossart, H. P., Keppler, F., & Isenbeck-Schröter, M. (2020). High Spatiotemporal Dynamics of Methane Production and Emission in Oxic Surface Water. Environmental Science & Technology, 54(3), 1451-1463.
• M. Bižić, T. Klintzsch, D. Ionescu, M. Y. Hindiyeh, M. Günthel, A. M. Muro-Pastor, W. Eckert, T. Urich, F. Keppler, H.-P. Grossart (2020). Aquatic and terrestrial cyanobacteria produce methane. Science Advances, 6, eaax5343.
• K. Lenhart, T. Klintzsch, G. Langer, G. Nehrke, M. Bunge, S. Schnell, F. Keppler (2016) Evidence for methane production by the marine algae Emiliania huxleyi, Biogeosciences. 13, 3163-3174.