1. National Environmental Research Institute; Department of Freshwater Ecology; Vejls⊘vej 25 8600 Silkeborg Denmark
2. Jordforsk, Frederik A. Dahls Vei 20 N-1432 Ås Norway
3. Norwegian University of Life Sciences; Department of Plant and Environmental Sciences; Box 5003 N-1432 Ås Norway
4. Leibniz-Institute of Freshwater Ecology and Inland Fisheries; Müggelseedamm 310 12587 Berlin Germany
5. Danish Institute of Agricultural Sciences; Department of Agroecology; Blichers Allé, Postbox 50 8830 Tjele Denmark
6. Alterra, Wageningen UR; PO Box 47 6700 AA Wageningen the Netherlands