SPECIES OF THE DIATOM GENUS PSEUDONITZSCHIA IN AUSTRALIAN WATERS

An Australia-wide taxonomic survey for species of the potentially toxic diatom genus Pseudonitzchia Peragallo (causative organisms of amnesic shellfish poisoning) was carried out using both light and transmission electron microscopy. Samples studied derived from the Gulf of Carpentaria, North West Shelf, Coral Sea, East Australian Current, Tasmanian, Victorian and Western Australian coastal waters. The dominant bloom-forming Pseudonitzchia species in Australian coastal waters were P. fraudulenta (New South Wales), P. pungens f. pungens and P. pseudodelicatissima (Tasmanian and Victorian waters). Other representatives of this 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 from the Bay of Fundy (Canada) can be weakly toxic, wild and cultured diatom populations of this species from Tasmanian and Victorian coastal waters were consistently nontoxic. The major toxic Pseudonitzschia species of concern in Canadian waters, P. pungens f. multiseries was detected 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 Australian waters. Surveys to identify bloom-forming Pseudonitzschia species in Australian waters, and monitoring of these species for toxicity, will continue.