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Empirical study of cyanobacterial toxicity along a trophic gradient of lakes

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A series of 22 lakes in southern Quebec spanning a wide trophic range were sampled to develop models of changes in cyanobacterial abundance and toxicity. All lakes contained toxic cyanobacteria, and epilimnetic toxin content, expressed as microcystin equivalents, was best predicted by total nitrogen concentration and total phosphorus concentration (TP). Although phytoplankton biomass increased linearly with increases in TP among lakes, toxigenic biomass increased as greater than the squared power of TP. The only potentially toxigenic genera whose biomass was correlated with microcystin concentration were Microcystis and Anabaena. Surprisingly, the best model for toxic-species biomass was based on epilimnetic nitrogen. The level of the hepatotoxin microcystin per unit biomass in these organisms did not vary markedly among lakes, supporting the idea that environmental factors control the occurrence, but have only a limited effect on the toxicity, of potentially toxic species.

Nous avons échantillonné une série de 22 lacs du sud du Québec couvrant une large gamme trophique afin de mettre au point des modèles du changement d'abondance et de toxicité des cyanobactéries. Tous les lacs contiennent des cyanobactéries toxiques et le contenu de toxines dans l'épilimnion, exprimé en équivalents de microcystine, est prédit le mieux par les concentrations d'azote total (TN) et de phosphore total (TP). Bien que la masse du phytoplancton s'accroisse de façon linéaire en fonction de l'accroissement de TP parmi les lacs, la biomasse des toxigènes augmente plus rapidement que la puissance au carré de TP. Les seuls genres potentiellement toxigènes dont la biomasse est en corrélation avec la concentration de microcystine sont Microcystis et Anabaena. De façon inattendue, le meilleur modèle de la biomasse des espèces toxiques est basé sur l'azote de l'épilimnion. La concentration chez ces organismes de l'hépatotoxine microcystine par unité de biomasse ne varie pas considérablement d'un lac à l'autre, ce qui appuie la proposition que les facteurs du milieu contrôlent la présence des espèces potentiellement toxiques, mais qu'ils ont un effet limité sur leur toxicité.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: September 1, 2005

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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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