Distribution of Dinophysis species in the Bay of Biscay and possible transport pathways to Arcachon Bay

Dinophysis is the most harmful toxic phytoplankton on the French coast in terms of its impact on local economy and public health. In Arcachon Bay, Dinophysis spp. have periodically affected shellfish industry for the last ten years; the most important events are analysed in detail in this paper. Regular monitoring revealed that these events originated outside Arcachon Bay in the open ocean. Data from 14 surveys and two coastal networks showed that Dinophysis was primarily found in the vicinity of Capbreton, 100 km south of the mouth of Arcachon Bay. The Dinophysis distribution on the continental shelf was determined during two surveys in 2005 and 2008: the highest concentrations were located along the coast and reached 18 000 cells.L− 1. Analysis of available current data revealed that strong westerlies lead to northward currents of up to 19 cm.s− 1. These marine meteorological conditions were frequently observed just prior to Dinophysis events and lead us to suggest that northward currents transport Dinophysis from the Capbreton area to Arcachon Bay.