SPECIES OF THE DIATOM GENUS PSEUDONITZSCHIA IN AUSTRALIAN WATERS

An Australia-wide taxonomic survey for species of the potentially toxi c diatom genus Pseudonitzchia Peragallo (causative organisms of amnesi c shellfish poisoning) was carried out using both light and transmissi on electron microscopy. Samples studied derived from the Gulf of Carpe ntaria, North West Shelf, Coral Sea, East Australian Current, Tasmania n, Victorian and Western Australian coastal waters. The dominant bloom -forming Pseudonitzchia species in Australian coastal waters were P. f raudulenta (New South Wales), P. pungens f. pungens and P. pseudodelic atissima (Tasmanian and Victorian waters). Other representatives of th is diatom genus in Australian waters include P. americana, P. lineola, P. subpacifica and P. turgidula, but these were usually only present in low concentrations. While populations of P. pseudodelicatissima fro m the Bay of Fundy (Canada) can be weakly toxic, wild and cultured dia tom populations of this species from Tasmanian and Victorian coastal w aters were consistently nontoxic. The major toxic Pseudonitzschia spec ies of concern in Canadian waters, P. pungens f. multiseries was detec ted as a minor component (5% of total biomass) of a dense P. pungens f . pungens bloom in a New South Wales estuary. Pseudonitzchia australis , a toxic species in Californian waters, was never detected in Austral ian waters. Surveys to identify bloom-forming Pseudonitzschia species in Australian waters, and monitoring of these species for toxicity, wi ll continue.