Identification of potentially toxic Pseudo-nitzschia (Bacillariophyceae) in New Zealand coastal waters, using lectins

Identification of species within the domoic acid-producing diatom genus Pse udo-nitzschia is vital for biotoxin monitoring and decisions regarding shel lfish harvesting, particularly when blooms are occurring. Several Pseudo-ni tzschia species produce high concentrations of domoic acid per cell, wherea s others are non-toxic, but all have similar morphologies using standard br ightfield light microscopy. FITC-conjugated lectins discriminated between t he New Zealand derived species tested in this study, except for P. delicati ssima and P. pseudodelicatissima. These results differ from those reported for Pseudo-nitzschia species isolated from Galician (Spanish) waters, which suggests variability in production of surface sugars by these diatoms depe nding on geographical origin and/or environmental conditions. Ribosomal RNA -targeted oligonucleotide probes, at present being field trialled in severa l countries including New Zealand and the United States, are therefore stil l the preferred method of Pseudo-nitzschia species identification underpinn ing New Zealand's biotoxin risk assessment programmes.