Harmful dinoflagellate cysts found in surface sediments around Fukue Island of west Kyushu,Japan

In the early spring of 1997, an outbreak of paralytic shellfish poisoning due to ingestion of wild oysters occurred at a coast of Tamanoura Bay in Fukue Island, Goto, west Japan. To clarify causative organisms for this incident, dinoflagellate cysts were examined in surface sediments collected from 12 stations of Tamanoura Bay, Kishuku Bay and Togi Bay of Fukue Island. More than 18 genera including 32 species of dinoflagellate cysts were identified and cyst densities in these samples ranged from 442 (GKS-st. 1) -2070 (GTU-st. 6) cells/ml. A small amount of living cysts of Gymnodinium catenatum, and probable cysts of Alexandrium catenella/tamarense, A. andersonii, and A. minutum were also found. In the plankton sample collected from the same stations of the sediment samples in Tamanoura Bay after the incident, A. andersonii was most dominated, but any of A. catenella, A. tamarense or G. catenatum was not observed. Based on these evidences, either A. andersonii or G. catenatum was pointed out to be causative species for this PSP incident