PHYTOPLANKTON SELECTION BY MUSSELS, AND DIARRHETIC SHELLFISH POISONING

To better understand the dynamics of diarrhetic shellfish poisoning (D SP) contamination a held study was carried out on the feeding behavior of Mytilus galloprovincialis (Lmk) during an important DSP outbreak. The study was focused on the relationships between phytoplankton in se awater and algal cells, or their remnants, in mussel stomachs. During the period studied, M. galloprovincialis seemed to feed selectively on dinoflagellates rather than diatoms. Further selection was observed a mong different dinoflagellate genera, a preference for the genus Dinop hysis being particularly evident. In addition, mussels seemed to open the thecae of Dinophysis cells and digest them more easily than other dinoflagellates. Due to the high variability of the results of phytopl ankton analysis in the mussel stomachs, no correlation was found betwe en the abundance of Dinophysis species in the mussels' stomachs and th e content of okadaic acid plus dinophysis-toxin-1 in their digestive g lands, evaluated with an ELISA assay. Conversely, the presence of Dino physis fortii (the main DSP-causative agent in the area studied) in in tegrated net samples of the whole water column and the toxin content o f the digestive glands presented similar temporal trends.