Abstract

In the early fall of 1996, a bloom of the toxic dinoflagellate Alexandrium catenella occurred in a fjord in the southern part of Chile that resulted in very high levels of paralytic shellfish poisoning (PSP) toxicity (up to 113,259 ?g of STX Eq/100 g) in shellfish in this area. The specific toxicity and PSP-toxin profiles within one series of filter-feeding bivalve mollusc (Aulacomya ater) and two carnivorous gastropods (Concholepas concholepas and Argobuccinum ranelliformes) were determined in whole shellfish or, in the case of the gastropods, separately in the digestive gland and foot muscle tissues by a postcolumn derivatization high-performance liquid chromatography method. The bivalve A. ater contained 11 of the 12 PSP-toxin derivatives analyzed. Gonyautoxin derivatives, mainly GTX2 and GTX1 and also GTX3, GTX4, and GTX5, were responsible for 86% of the total toxin content. Other derivatives, present in lesser amounts, included neoSTX, STX, C1, C2, and C4. The highest levels of toxicity measured in A. ater occurred 25 days after the highest cell number (3.1 x 104 cells/L) of A. catenella were observed within the water column, and high, although diminishing, levels of toxicity persisted in the bivalves for more than 6 mo after the dinoflagellate bloom. In contrast, the carnivorous gastropods achieved their highest toxicity about 5 mo after the bloom. In both cases, the toxicity within the digestive glands far exceeded the levels in the foot muscle; in the case of A. ranelliformes, toxicity in the latter portion was almost undetectable. This is the first quantitative study of PSP-toxin content in these shellfish in this part of the world and shows the natural accumulation and depuration rates of PSP toxins after an outstanding outbreak of A. catenella. The sequence of increasing contamination and also the temporal association between the three native molluscs are shown and discussed.