1. Natural Resources Institute Finland (Luke), P.O. Box 2, FI-0790 Helsinki, Finland
2. Groupe de Recherche en Ecologie Arctique, F-21440 Francheville, France
3. Université de Bourgogne Franche Comté, Equipe Ecologie-Evolution, UMR 6282 Biogéosciences, F-21000 Dijon, France
4. Department of Arctic and Marine Biology, The Arctic University of Norway, N-9047 Tromsø, Norway
5. Section of Ecology, Department Biology, FI-20014 University of Turku, Finland