Relationship between occurrence of Dinophysis species (Dinophyceae) and shellfish toxicity

Between 1994 and 1999 the relationship between Dinophysis species and diarrhetic shellfish toxins (DST) in blue mussel (Mytilus edulis) was studied in Flodevigen Bay on the south coast of Norway. The concentrations of CIA a, Dinophysis acuminata, D. acuta and D. norvegica were quantified every Monday, Wednesday and Friday, and approximately fortnightly DST occurrences in blue mussel (Al. edulis) were analysed by mouse bioassay. In addition, we report a separate study of DST in blue mussel and Dinophysis spp., based on HPLC analysis. The highest concentrations of DST in blue mussel were observed during the low productivity period from November to February. Shortly after the onset of the spring phytoplankton bloom, DST in blue mussel dropped to zero and remained low until September. There was no relationship between DST in blue mussel and the concentrations of D, acuminata and D. norvegica. Dinophysis acuta was probably the main Source of DST in blue mussel. There was, however, no clear relationship between the concentrations of D. acuta and DST in blue mussel. The results suggest that the DST content in D. acuta cells was highly variable, with the highest concentrations observed at the end of the growth season in November and December. In addition, the accumulation of DST seemed to be counteracted in the presence of high concentrations of alternative food sources for blue mussel. On the basis of this study, we suggest a new strategy for monitoring DST in shellfish on the south coast of Norway.