Monthly variations in diarrhetic toxins and yessotoxin in shellfish from coast to the inner part of the Sognefjord, Norway

Monthly concentrations of diarrhetic shellfish poisoning (DSP) toxins and y essotoxin (YTX) in mussels from the coast to the inner part of the Sognefjo rd were determined. Mussels from nine locations were sampled from March to November 1997. The DSP toxins and YTX were analysed by a colorimetric prote in phosphatase 2A (PP2A) inhibition assay or fluorometric HPLC, respectivel y. The mouse bioassay for DSP toxins was performed including either chlorof orm or diethyl ether in the final step of extraction. Using ether in the fi nal step normally facilitated extraction of the DSP toxins, okadaic acid (O A) and dinophysis toxin-1 (DTX-1), while chloroform extraction included a w ider spectrum of toxins, including YTX and a fast acting toxin(s) with neur otoxic effects. The concentrations of DSP toxins and YTX in mussels increas ed with distance from the coast. The highest concentrations of YTX (574 mug YTX/100 g mussel meat) and diarrhetic toxins (349 mug OA equivalents/100 g mussel meat) were measured in May and August, respectively, at locations i n the inner part of the fjord. Since concentrations of DSP toxins and YTX i n mussels increased with distance from the coast, the locations for mussel farming in the Sognefjord close to the coast, seem to be preferable. (C) 20 01 Elsevier Science Ltd. All rights reserved.