1. Department of Biological Sciences and Groupe de Recherche Universitaire en Limnologie et en Environnement Aquatique (GRIL), University of Québec at Montréal, C.P. 8888, Succ. Centre-Ville, Montréal, QC H3C 3P8, Canada
2. Departamento de Ecologia, Universidade Federal do Rio de Janeiro, CCS, IB, Caixa Postal 68020, cep 21941-970, Rio de Janeiro, Brasil
3. United States Environmental Protection Agency, Office of Water, Washington, D.C. 20004 USA