1. Leibniz Institute of Freshwater Ecology and Inland Fisheries, Department of Ecohydrology and Biogeochemistry, Mueggelseedamm 301, D-12587 Berlin, Germany
2. Brandenburg University of Technology Cottbus-Senftenberg, Department of Aquatic Ecology, Seestraße 45, D-15526 Bad Saarow, Germany
3. Department of Microbiology and Biotechnology, University of Hamburg, Ohnhorststraße 18, D-22609 Hamburg, Germany
4. Leibniz Institute of Freshwater Ecology and Inland Fisheries, Department of Plankton and Microbial Ecology, Zur Alten Fischerhuette 2, 16775 Stechlin, Germany
5. Institute of Biochemistry and Biology, Potsdam University, Maulbeerallee 2, D-14469 Potsdam, Germany