1. Unitat de Limnologia; Departament d'Ecologia i Centre de Recerca d'Alta Muntanya; CEAB-CSIC-Universitat de Barcelona; 08028 Barcelona Catalonia Spain
2. Department of Microbial Biotechnology; Centro Nacional de Biotecnología-CSIC; Darwin 3, Campus de Cantoblanco; 28049 Madrid Spain
3. Department of Aquatic Microbial Ecology; Biology Centre of the Academy of Sciences of the Czech Republic; Institute of Hydrobiology; Na Sádkách 7 CZ-370 05 České Budějovice Czech Republic
4. Limnological Station, Institute of Plant Biology, University of Zurich; Seestrasse 187 CH-8802 Kilchberg Switzerland