1 Limnological Station, Department of Plant and Microbial Biology, University of Zurich, Kilchberg, Switzerland.
2 Department of Aquatic Microbial Ecology, Institute of Hydrobiology, Biology Centre of the Czech Academy of Sciences, České Budějovice, Czech Republic.
3 Limnological Station, Department of Plant and Microbial Biology, University of Zurich, Kilchberg, Switzerland. [email protected].