1. Program Man-Society-Environment; Department of Environmental Sciences; University of Basel; Vesalgasse 1 CH-4051 Basel Switzerland
2. Research Centre for Sustainable Energy and Water Supply; University of Basel; Peter Merian Weg 6 CH-4002 Basel Switzerland
3. Limnological Institute; University of Konstanz; Mainaustrasse 252 D-78457 Konstanz Germany
4. Zoological Institute of the University of Cologne; Department of General Ecology & Limnology; Ecological Field Station Grietherbusch; D-50923 Cologne Germany
5. Department of Biological Sciences; University of Alberta; 11455 Saskatchewan Drive Edmonton AB Canada