1. Department of Biological Sciences, University of Alberta, Edmonton, Alberta Canada T6G 2E9, Department of Chemistry, Trent University, Peterborough, Ontario, Canada K9J 7B8, Department of Environment and Geography, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2, Centre St-Laurent, Aquatic Ecosystem Protection Research Division, Water Science and Technology Directorate Science and Technology Branch, Environment Canada, 105 rue McGill, Montréal, Québec, Canada H2Y 2E7