Temporal and spatial distribution of the ichthyotoxic dinoflagellate Gyrodinium aureolum Hulburt in the St Lawrence, Canada

The occurrence of the potentially ichthyotoxic dinoflagellate Gyrodinium aureolum Hulburt is reported for the first time in the Lower Estuary and Gulf of St Lawrence. Taxonomic identification using an iramunochemical tagging method suggests a close taxonomic proximity between the species found in the St Lawrence and G.aureolum present in European waters. In 1993, G.aureolum was observed along the entire coast of Quebec and in offshore waters of the Gulf of St Lawrence. At the coastal stations, G.aureolum showed large week-to-week variations, but higher densities were observed during late August and early September. Bloom concentrations (106 cells 1−1) were only observed in the Gaspé Current at Mont-Louis, on the north coast of the Gaspd peninsula. In the central part of the Gulf, G.aureolum was concentrated in the upper 5 m of the stations directly influenced by the freshwater run-off of the St Lawrence Estuary. Results from principal component analysis indicate that G.aureolum favors environments with high nitrogen recycling activity

Financial support for this research was provided by the Department of Fisheries and Ocean and the National Science and Engineering Research Council of Canada (individual grants to M.L. and M.Gosselin). This study was also funded in part by Fonds pour la Formation de Chercheurs et l'Aide a la Recherche. This is a contribution of the Toxic Algae Program of the Maurice Lamontagne Institute (Quebec)

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