Gymnodinium catnatum blooms and shellfish toxicity in southern Tasmania, Australia

Dinoflagellate blooms of Gymnodinium catenatum (10⁴ to 10⁶ cells l^-1 ) in two southern Tasmanian estuaries in 1986 and 1987 resulted in PSP concentrations in mussels of up to 8350 micrograms/100 g. The dinoflagellate populations showed an unusually long growth season (December until June), at water temperatures of 12 to 18 C, sometimes following heavy rainfall events. Patterns of shellfish toxicity are discussed in relationship to dinoflagellate abundance, local hydrography, benthic cyst beds and shellfish feeding.