Zooplankton as a potential vector of diarrhetic shellfish poisoning toxins through the food web

This study was carried out during an autumn bloom of Dinophysis acuminata in the Galician Rias Bajas (NW Spain). The main objective was to determine whether any of the predominant zooplankton species could ingest and transfer toxins through the pelagic food web. Grazing experiments showed that the copepods Temora longicornis and Oithona nana and the tintinnid Favella serrata fed on Dinophysis spp. whereas the copepods Acartia clausi and Euterpina acutifrons did not. However, only E serrata seem to profit from the ingestion of the toxic dinoflagellates. Field populations of F serrata increased whereas T. longicornis and O. nana densities declined after the toxic outbreak. Okadaic acid content found in the seston size fractions 100-200, 200-300 and 300-1000 mu m showed a good correlation with F. serrata. These results confirm the hypothesis that tintinnids can transfer dinoflagellates toxins to higher trophic levels in the pelagic food web. The importance of faecal pellets with undigested dinoflagellates as an alternative pathway to transmit toxins to pelagic or benthic organisms is mentioned.