The first report of the potentially harmful diatom Pseudo-nitzschia caciantha from Australian coastal waters

Abstract

The diatom Pseudo-nitzschia is a significant component of coastal waters worldwide and a producer of the potent neurotoxin, domoic acid. Sixteen species belonging to this genus have been reported from Australian waters, but the potentially toxic species P. caciantha has not been previously known from this region. Two clonal strains of P. caciantha were isolated from Coogee Beach, south-east Australia, and the morphological, molecular and toxicological evidence for this species delineation were examined using light and transmission electron microscopy, phylogenetic analysis based on sequences of the second internal transcribed spacer and domoic acid production as measured by liquid chromatography-mass spectrometry. The results unambiguously confirmed that these isolates are the potentially toxic species P. caciantha, being only the second report of this species in the Southern Hemisphere. The potential for further hidden Pseudo-nitzschia diversity in these waters is considerable.