Cyst and radionucleotide evidence for the recent introduction of the toxic dinoflagellate Gymnodinium catenatum into Tasmanian waters

Cysts of the dinoflagellate G}mnodin~l!ni catenaluni were present only in the top sections ot duplicate marine sediment corcs from Deep Bay In southern T a s m a n ~a , Austraha. ""Pb and '"CS analyses i n d ~c a t e that the appearance of the cyst of this toxic dinoflagellate (one of the causative organ-Isms of paralytic shellf~sh po~sonlng) occurred after 1972. This sedlment core evidenrc a n d the absence of this species from thc phytoplankton of most other neighbouring Australian waters suggest that Gyrnnodlnium catenatum is not endern~c to Tasmanla but has been introduced recently. This species was first seen In bloom proportions in Tasmania In 1980, w ~t h major blooms havlng occurred since then in 1986, 1991 and 1993. Several llnes of evidence suggest that ballast water discharge from cargo vessels originating from Japan and South Korea, or less likely Europe, is the most probable mechanism of introduction.