Methane formation from algae in oxic seawater

Background/Summary

The oceans are considered to be a source of CH4 to the atmosphere although the magnitude of total net emissions is highly uncertain and sources are not well described. To explain the source of CH4 in surface waters, it has been suggested that methanogenesis takes place in anoxic microenvironments of organic aggregates. Other sources such as in-situ formation of CH4 by algae have also been suggested, however, a direct evidence of algae-derived CH4 formation from lab experiments with (axenic) algae cultures is still missing, and thus so far the accumulation of CH4 in the upper water layer has not yet been related to a direct production by algae.

The overall aim of this research project is the verification (proof of principle) and quantification of CH4 production by several species of marine algae such as haptophytes (e.g. Emiliania huxleyi). Potential precursors such as (e.g. methyl sulfides and sulfoxides) of algae-derived CH4 will be identified by using stable isotope techniques. Several environmental factors will be investigated with respect to their effect of algae-derived CH4 production. Furthermore, we will apply various microbiological tests to screen for methanogenic Archaea or bacteria potentially involved in CH4 formation. We will also focus on factors sensitive to climate change such as temperature, oxygen concentration and nutrient availability. An interdisciplinary approach requiring the interaction of several disciplines is envisaged to realize the aims of the project. The results are expected to improve our understanding of biogeochemical cycling of CH4 formation in the oceans and to better explain the CH4-enrichment of oxygenated surface waters compared to atmospheric concentration, so-called “Oceanic methane paradox”.

Fig. 1: Emiliana huxleyi in culture.

Relevant publications

• T. Klintzsch, G. Langer, A. Wieland, H. Geisinger, K. Lenhart, G. Nehrke, F. Keppler (2020). Effects of temperature and light on methane production from widespread marine algae. Journal of Geophysical Research: Biogeosciences, 125, e2020JG005793. doi.org/10.1029/2020JG005793.
• T. Klintzsch, G. Langer, G. Nehrke, A. Wieland, K. Lenhart, F. Keppler (2019). Methane production by three widespread marine phytoplankton species: release rates, precursor compounds, and relevance for the environment. Biogeosciences, 16, 4129-4144.
• 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.