1. Norwegian Polar Institute, Tromsø, NO-9296, Norway, Department of Aquatic BioSciences, University of Tromsø, Tromsø, NO-9037, Norway, Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada, National Water Research Institute, Environment Canada, Burlington, Ontario L7R 4A6, Canada, Norwegian Institute for Air Research, Tromsø, NO-9296, Norway, and Canadian Wildlife Service, National Wildlife Research Centre, Environment Canada, Ottawa, Ontario K1A 0H3, Canada