Pseudo-Nitzschia Australis, Mytilus Edulis, Engraulis Anchoita And Domoic Acid In The Argentine Sea

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Pseudo-nitzschia australis, Mytilus edulis, Engraulis anchoita AND DOMOIC ACID IN THE ARGENTINE SEA Rubén M. Negri, Nora Montoya, José I. Carreto*, Rut Akselman and Daniela Inza.Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Mar del Plata, Argentina

Frenguelli in the Gulf San Matías (Argentina) first described Pseudo-nitzschia australis in 1939.Nevertheless, there has not been any toxicity episode associated with this species in the Argentine Sea. A bloom of P. australis was detected in July of 2000 at a fixed monitoring station near Mar delPlata. The species was identified by TEM, and reach an abundance of 28000 cells l-1. The presence of domoic acid was confirmed by HPLC in natural samples of phytoplankton, mussels (Mytilusedulis), and muscular tissue and gastrointestinal content of anchovies (Engraulis anchoita). The maximum value of domoic acid detected in the mussels (7,7 µg g-1) was below the safety limit forhuman consumption (20 µg g-1). The concentration of this neurotoxin was very high in the gastrointestinal content of anchovies (76,6 µg g-1), which also showed the presence of frustules of P.australis, while the values in the muscular tissue were lower (4,9 µg g-1). The development of the bloom coincided with the decrease in temperature (from 17 to 10°C) and the homogenization of thewater column during winter. In this period the salinity values were the highest, varying between 33,9 and 34,1 ups. Nutrient concentrations were high in the whole water column. These resultsconfirm that natural populations of P. australis do produce significant amounts of domoic acid, and that this neurotoxin is being transferred to benthic or pelagic filter feeding organisms. Wediscuss these results in comparison with similar events in other areas of the world, and in relationship to the strategies of monitoring domoic acid in different components of the biota.