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

Abstract

SUMMARY 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.

Recent Trends in Marine Phycotoxins from Australian Coastal Waters

“…Traditional light microscopy groupings indicate that the P. seriata group (cells >3 µm wide) is highest in abundance in the austral summer, autumn or spring (species dependent), while the P. delicatissima group (cells <3 µm wide) is in greatest abundance in winter and spring. Using morphological and molecular methods, seventeen species have been identified [ 7 , 102 , 103 ] with three species, Pseudo-nitzschia australis , Pseudo-nitzschia cuspidata and Pseudo-nitzschia multistriata , as confirmed DA producers (maximum DA 500 ng·mL −1 , 11 pg DA per cell and 25.4 pg DA per cell, respectively) [ 7 , 56 ]. Interestingly Pseudo-nitzschia multiseries , a consistent producer of DA in all other strains tested throughout the world, proved to be the first nontoxic strain in Australia [ 7 ].…”

A new diatom species P. hallegraeffii sp. nov. belonging to the toxic genus Pseudo-nitzschia (Bacillariophyceae) from the East Australian Current

“…micropora and P . hasleana [ 24 – 29 ]. All other Pseudo-nitzschia species identified thus far from Australian waters are crudely placed in the ‘ Pseudo-nitzschia seriata complex’ (mean valve width >3 μm) [ 5 , 59 ].…”

“…Seventeen species belonging to the genus Pseudo-nitzschia have been identified thus far in Australia [ 24 – 29 ]. This genus has been identified as a dominant member of the phytoplankton community in both the coastal upwelling regions and estuarine systems of eastern Australia [ 26 , 30 – 33 ].…”