Aerobic and anaerobic methane turnover in the water column of the central Baltic Sea (Gotland- and Landsort-Deep) 2011-2014

DFG-project (BL 971/3-1; 2011-2014) Dr. Martin Blumenberg (together with Prof. Dr. Volker Thiel)

Methane is one of the key-gases driving future and past climate changes. While aquatic systems in general – particularly within anoxic sediments - appear to be the most important sources of atmospheric methane, oceans are only minor sources. This is due to microbial turnover already in anoxic sediments columns (sulfate-dependent anaerobic oxidation of methane; AOM) which consumes more than 90% of the methane before it enters the atmosphere. Knowledge on methanotrophy in water columns, however, is limited. In the Gotland- and Landsort-Deep in the central Baltic Sea density differences between upper and deeper waters lead to the establishment of methane-rich (Schmale et al., 2010), anoxic conditions in the deep. Preliminary data suggest that, similar to the Black Sea (Blumenberg et al., 2007), major methanotrophy occurs in the redoxcline. However, the distinct microorganisms, if anaerobic microorganisms using sulfate, nitrite, iron or manganese for methanotrophy are present, and the relevance of individual groups are also unknown.

The joint project of scientists from the Geoscience Center at the University Göttingen and the IOW (Dr. Oliver Schmale) aims at:

  • the quantification of methane-consuming processes in the water column of the Gotland- and Landsort-Deep and
  • the identification of methanotrophic key-players in the water columns using molecular-microbiological and organic-geochemical methods and at trying to reconstruct the methane-cycle in the geological record (sediments).

In the Geobiology Group of the Geoscience Center organic-geochemical biosignatures, namely biomarkers, are used for these purposes. Among other, bacteriohopanepolyols which are specific for aerobic methanotrophic bacteria are used to characterize the distribution and abundances of these microorganisms in the individual water depths of the Gotland- and Landsort-Deeps. Further, those and other (intact) lipids shall be used i order to get information on the geological history of methane-cycling in the central Baltic Sea. Samples will be taken during various research cruises (e.g., with RV Schwedeneck, August 2011).

Contact

Prof. Dr. Volker Thiel (vthiel@gwdg.de; Tel. 0551-39-14395)
Dr. Martin Blumenberg (martin.blumenberg@bgr.de; Tel. 0511 643 2853)

References

Blumenberg, M., Seifert, R., Michaelis, W. (2007) Aerobic methanotrophy in the oxic-anoic transition zone of the Black Sea. Organic Geochemistry 38, 84-91.
Schmale, O., Schneider von Deimling, J., Gülzow, W., Nausch, G., Wanick, J.J., Rehder, G. (2010) Distribution of methane in the water column of the Baltic Sea. Geophysical Research Letters 37, L12604.


For further details or paper requests please contact Martin Blumenberg.

contact:

martin.blumenberg@bgr.de