1. Department of Environmental Physics, Swiss Federal Institute of Environmental Science and Technology (EAWAG), Überlandstrasse 133, CH-8600 Dübendorf, Switzerland
2. Geobotanical Institute, University of Berne, Altenbergrain 21, CH-3013 Berne, Switzerland
3. Okanagan Institute for Freshwater Studies and Department of Biology, North Kelowna Campus, Okanagan University College, 3333 College Way, Kelowna, British Columbia, Canada V1V 1V7