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High microcystin concentrations occur only at low nitrogen-to-phosphorus ratios in nutrient-rich Canadian lakes

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Although the cyanobacterial toxin microcystin has been detected in Canadian fresh waters, little is known about its prevalence on a national scale. Here, we report for the first time on microcystin in 246 water bodies across Canada based on 3474 analyses. Over the last 10 years, microcystins were detected in every province, often exceeding maximum guidelines for potable and recreational water quality. Microcystins were virtually absent from unproductive systems and were increasingly common in nutrient-rich waters. The probable risk of microcystin concentrations exceeding water quality guidelines was greatest when the ratio of nitrogen (N) to phosphorus (P) was low and rapidly decreased at higher N:P ratios. Maximum concentrations of microcystins occurred in hypereutrophic lakes at mass ratios of N:P below 23. Our models may prove to be useful screening tools for identifying potentially toxic “hotspots” or “hot times” of unacceptable microcystin levels. A future scientific challenge will be to determine whether there is any causal link between N:P ratios and microcystin concentrations, as this may have important implications for the management of eutrophied lakes and reservoirs.

Document Type: Rapid Communication


Affiliations: 1: Department of Biological Sciences, University of Alberta, 11455 Saskatchewan Drive, Edmonton, AB T6G 2E9, Canada. 2: Département des Sciences Biologiques, Université du Québec à Montréal, C.P. 8888, Succursale Centre-ville, Montréal, QC H3C 3P8, Canada. 3: Acadia Centre for Estuarine Research, 23 Westwood Avenue, Acadia University, Wolfville, NS B4P 2R6, Canada. 4: Shenzhen University, Shenzhen, Guangdong Province, P.R. China. 5: Limnology Laboratory, Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada 6: Alberta Centre for Toxicology, Department of Physiology & Pharmacology, Faculty of Medicine, University of Calgary, Calgary, AB T2N 4N1 Canada. 7: Departemento de Botânica, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, C.P. 48631270-010, Belo Horizonte, MG, Brazil. 8: Algal Taxonomy and Ecology Inc., 31 Laval Dr., Winnipeg, MB R3T 2X8, Canada. 9: AlgalTox International, P.O. Box 268, Pine Falls, MB R0E 1M0, Canada. 10: Agri-Environment Services Branch, Agriculture and Agri-Food Canada, 9700 Jasper Avenue, Edmonton, AB T5J 4C3, Canada. 11: Aquatic Ecosystem Management Research Division, Science & Technology Branch, Environment Canada, National Water Research Institute, 867 Lakeshore Road, Bington, ON L7R 4A6, Canada. 12: Water Policy Branch, Alberta Environment, 7th Floor Oxbridge Place, 9820-106 Street, Edmonton, AB T5K 2J6, Canada.

Publication date: September 14, 2012

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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