Molecular Identification of Gambierdiscus and Fukuyoa (Dinophyceae) from Environmental Samples

Ciguatera Fish Poisoning (CFP) is increasing across the Pacific and the distribution of the causative dinoflagellates appears to be expanding. Subtle differences in thecal plate morphology are used to distinguish dinoflagellate species, which are difficult to determine using light microscopy. For these reasons we sought to develop a Quantitative PCR assay that would detect all species from both <i>Gambierdiscus</i> and <i>Fukuyoa</i> genera in order to rapidly screen environmental samples for potentially toxic species. Additionally, a specific assay for <i>F. paulensis</i> was developed as this species is of concern in New Zealand coastal waters. Using the assays we analyzed 31 samples from three locations around New Zealand and the Kingdom of Tonga. Fourteen samples in total were positive for <i>Gambierdiscus</i>/<i>Fukuyoa</i> and two samples were also positive using the <i>F. paulensis</i> assay. Samples from the Kermadec Islands were further characterized using high-throughput sequencing metabarcoding. The majority of reads corresponded to <i>Gambierdiscus</i> species with three species identified at all sites (<i>G. australes</i>, <i>G. honu</i> and <i>G. polynesiensis</i>). This is the first confirmed identification of <i>G. polynesiensis</i>, a known ciguatoxin producer, in New Zealand waters. Other known toxin-producing genera were also detected, included <i>Alexandrium</i>, <i>Amphidinium</i>, <i>Azadinium</i>, <i>Dinophysis</i>, <i>Ostreopsis</i>, and <i>Prorocentrum</i>.