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

Dinophysis is the most harmful toxic phytoplankton on the French coast in terms of its impact on local economyand public health. In Arcachon Bay, Dinophysis spp. have periodically affected shellfish industry for thelast ten years; the most important events are analysed in detail in this paper. Regular monitoring revealedthat these events originated outside Arcachon Bay in the open ocean. Data from 14 surveys and two coastalnetworks showed that Dinophysis was primarily found in the vicinity of Capbreton, 100 km south of themouth of Arcachon Bay. The Dinophysis distribution on the continental shelfwas determined during two surveysin 2005 and 2008: the highest concentrationswere located along the coast and reached 18000 cells.L−1. Analysisof available current data revealed that strong westerlies lead to northward currents of up to 19 cm.s−1. Thesemarinemeteorological conditionswere frequently observed just prior to Dinophysis events and lead us to suggestthat northward currents transport Dinophysis from the Capbreton area to Arcachon Bay.