Etude des relations entre le phytoplancton et les phénomènes de toxicité d’origine inconnue dans le Bassin d'Arcachon

Since the introduction of the oyster Crassostrea gigas in the Arcachon Basin, the sale of oysters has been banned for the first time in 2005, based on mouse bioassay positive for lipophilic toxins. If the beginning of this episode could be related to the presence in water of microalgae of the genus Dinophysis and okadaic acid in the hepatopancreas of oyster, it has not been the same for the end of the period, which was qualified as of "atypical toxicity episode" or "toxicity of unknown origin", that is to say, "an episode of shellfish contamination, revealed in a toxic response in mice by intraperitoneal injection , whose origin can not be explained by the presence of known toxins usually sought”. Between 1993 and 2009, 7 episodes Dinophysis or okadaic acid (OA) were identified (in 1995, each year from 2002 to 2006 and again in 2008). The first events of unusual toxicity appeared in 2004 on the mussels. They then quickly took the scale, 17 episodes of toxicity of unknown origin have been identified between 2004 and 2009, for the past two years, reaching a period of four months. The aim of this work, included in a program led by AFSSA, was to characterize these toxic events and try to put them in touch with the evolution of phytoplankton populations that develop in the Arcachon Basin.