Control of lipophilic shellfish poisoning outbreaks by seasonal upwelling and continental runoff

Closures of mussel rafts in the Ria de Ares-Betanzos (NW Spain) because of the occurrence of lipophilic shellfish poisoning outbreaks over the period 1999-2007 have been studied in relation to the coastal wind and precipitation regimes of the area. More than 85% of the episodes concentrate on the summer and autumn that coincide with the upwelling-favourable/dry season and the transition to the downwelling-favourable/wet season, respectively. We obtain that the percentage of days closed in summer can be predicted by the average continental runoff (Qr) during the preceding spring (86% of the variance explained by the average Qr of May) and the percentage of days closed in autumn by the average offshore Ekman transport (Ek(L)) during the preceding summer (91% of the variance explained by the average EkL of August). A rainy spring will produce extensive closures in summer and a windy summer extensive closures in autumn. We speculate that this seasonal lag between atmospheric forcing and lipophilic shellfish poisoning outbreaks, which provides a chance to forecast mussel toxicity, is compatible with the obligate mixotrophic nutritional mode of the Dynophysis acuminata complex, the dominant lipophilic shellfish poisoning species in the Ria de Ares-Betanzos. (C) 2010 Elsevier B.V. All rights reserved.