Abstract

Paralytic shellfish toxin profiles of Alexandrium tamarense (Lebour) Balech and mussels (Aulacomya ater) contaminated by the dinoflagellate, were obtained from eight sampling stations along the Valdes Peninsula, Chubut, Argentina. The samples were collected from November 1995 to May 1996. The data show, that the monitoring began after an outbreak during a bloom of A. tamarense. The highest cell densities were found in November 1995 at Bengoa (1.81 x 103 cells/L) and Larralde (1.2 x 103 cells/L), both stations are located in the San Jose Gulf. Occurrence of other species of phytoplankton are also reported. A. tamarense was never more than 2% of the total phytoplankton population. Low temperatures and high salinity were found in November 1995, when the highest A. tamarense cell density was observed. Using a postcolumn derivatization high-performance liquid chromatography (HPLC) analysis, the PSP toxin profiles of Patagonian coast phytoplankton and mussel samples were obtained for the first time. The average PSP toxin profile of over 30 mussel samples from all monitoring stations showed the gonyautoxins 1-4 (GTX 1-4) epimers to be the most abundant PSP toxins. These epimers were the most prevalent ones in the A. tamarense present in the phytoplankton samples analyzed. Other PSP toxins quantified in mussel samples were: STX, dcSTX, and C1-C4. NeoSTX was never found in mussel or phytoplankton samples. The highest toxicity in the phytoplankton samples was 490 fmol of PSP toxins/cell and mussels 631 ?g STX eq./100 g, both of which were obtained in November, 1995. The decrease of the toxicity in the filter feeder Aulacomya ater, occurs following an exponential decay of the first order, showing that, in the San Jose Gulf, Valdes Peninsula, the natural depuration process of A. ater can be interpreted by a one-compartment model. According to the detoxification rate determined for A. ater, a native South American filter-feeder bivalve, can be classified as a moderate detoxifier.