1 Eawag, Department of Aquatic Ecology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland; University of Zurich, Department of Evolutionary Biology and Environmental Studies, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. Electronic address: isabelle.gounand@eawag.ch.
2 University of Toronto, Department of Ecology and Evolutionary Biology, 25 Wilcocks Street, M5S 3B2 Toronto, ON, Canada.
3 Eawag, Department of Aquatic Ecology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland; University of Zurich, Department of Evolutionary Biology and Environmental Studies, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.