1. Norwegian Institute of Nature Research, Dept. of Arctic Ecology, FRAM – High North Research Centre for Climate and the Environment , P.O. Box 6606 Langnes , NO-9296 Tromsø , Norway
2. Norwegian Institute of Nature Research, Dept. of Aquatic Biodiversity , P.O. Box 5685 Torgarden, NO-7485 Trondheim , Norway
3. Centre of Biodiversity Dynamics, Norwegian University of Science and Technology (NTNU) , NO-7491 Trondheim , Norway