1. Department of Aquatic Ecology; Eawag, Swiss Federal Institute of Aquatic Science and Technology; Überlandstrasse 133, 8600 Dübendorf Switzerland
2. Institute of Integrative Biology, Department of Environmental Systems Science, ETH Zürich; Universitätsstrasse 16, 8092 Zürich Switzerland
3. Department of Biology; University of Victoria; 3800 Finnerty Road, Victoria BC V8P 5C2 Canada