TEMPORAL AND SPATIAL-DISTRIBUTION OF THE ICHTHYOTOXIC DINOFLAGELLATE GYRODINIUM-AUREOLUM HULBURT IN THE ST-LAWRENCE, CANADA

The occurrence of the potentially ichthyotoxic dinoflagellate Gyrodini um aureolum Hulburt is reported for the first time in the Lower Estuar y and Gulf of St Lawrence. Taxonomic identification using an immunoche mical tagging method suggests a close taxonomic proximity between the species found in the St Lawrence and G. aureolum present in European w aters In 1993, G. aureolum was observed along the entire coast of Queb ec and in offshore waters of the Gulf of St Lawrence. At the coastal s tations, G. aureolum showed large week-to-week variations, but higher densities were observed during late August and early September. Bloom concentrations (10(6) cells l(-1)) were only observed in the Gaspe Cur rent at Mont-Louis, on the north coast of the Gaspe 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 indica te that G. aureolum favors environments with high nitrogen recycling a ctivity.