Paralytic shellfish toxins in mussels and Alexandrium tamarense at Valdes Peninsula, Chubut, Patagonia, Argentina: Kinetics of a natural depuration

Paralytic shellfish toxin profiles of Alexandrium tamarense (Lebour) Balech and mussels (Aulacomya ater) contaminated by the dinoflagellate, were obta ined from eight sampling stations along the Valdes Peninsula, Chubut, Argen tina. The samples were collected from November 1995 to May 1996. The data s how, that the monitoring began after an outbreak during a bloom of A. tamar ense. The highest cell densities were found in November 1995 at Bengoa (1.8 1 x 10(3) cells/L) and Larralde (1.2 x 10(3) cells/L), both stations are lo cated in the San Jose Gulf. Occurrence of other species of phytoplankton ar e also reported. A. tamarense was never more than 2% of the total phytoplan kton population. Low temperatures and high salinity were found in November 1995, when the highest A. tamarense cell density was observed. Using a post column derivatization high-performance liquid chromatography (HPLC) analysi s, the PSP toxin profiles of Patagonian coast phytoplankton and mussel samp les 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 t he most prevalent ones in the A. tamarense present in the phytoplankton sam ples analyzed. Other PSP toxins quantified in mussel samples were: STX, dcS TX, and C1-C4. NeoSTX was never found in mussel or phytoplankton samples. T he highest toxicity in the phytoplankton samples was 490 fmol of PSP toxins /cell and mussels 631 mu g STX eq./100 g, both of which were obtained in No vember, 1995. The decrease of the toxicity in the filter feeder Aulacomya a ter, occurs following an exponential decay of the first order, showing that , in the San Jase Gulf Valdes Peninsula, the natural depuration process of A. ater can be interpreted by a one-compartment model. According to the det oxification rate determined for A. ater, a native South American filter-fee der bivalve, can be classified as a moderate detoxifier.