A TOXIC DINOFLAGELLATE BLOOM AND PSP PRODUCTION ASSOCIATED WITH UPWELLING IN GOLFO-NUEVO, PATAGONIA, ARGENTINA

In 1980 Paralytic Shellfish Poison (PSP) was detected for the first time in Patagonia (Argentina), and has been recurring since during spring and summer. Human intoxications were recorded during the 1987/88 summer due to ingestion of mussels. In January, concentrations of 750000 cells l-1 were observed, decreasing to 3100 cells l-1 twenty days later. At the same time, values of 66 150. Mouse Unit (MU) 100 g-1 of meat were measured in Aulacomya ater (a bivalve mollusk). A decrease in the concentration of toxic plankton resulted in a concomitant decrease in MU values. The mean detoxification time was 7.6 days. However, mussels retained toxicity up to 50 days after the disappearance of cells. The upwelling of cold waters at the beginning of summer, could have been one of the causes that favoured a bloom of Alexandrium excavatum and of Prorocentrum micans. In March, an abundance of the diatom Skeletonema costatum coincided with high concentrations of silicate.