Sub-tropical benthic/epiphytic dinoflagellates of Aotearoa New Zealand and Rangitahua Kermadec Islands

Temperatures and temperature anomalies have been increasing in the sub-tropical regions of Aotearoa New Zealand and these changes may impact on harmful algal bloom (HAB) events. Benthic and epiphytic di-noflagellates, particularly the toxin producers, are the focus of this study as it is predicted that under future climate conditions they may produce more toxins or marine animals may become more susceptible to them. The results of past expeditions to Rangita over bar hua Kermadec Islands and sampling trips to Northland, Aotearoa New Zealand, are summarised and the results of the most recent trips to both regions are presented. The macroalgal habitats of the dinoflagellates are also characterised. Dinoflagellate species not previously identified in Ran-gita over bar hua include Coolia canariensis, C. palmyrensis, and C. tropicalis, all identified by DNA sequencing of the large subunit ribosomal RNA region. Gambierdiscus polynesiensis was again isolated and produced 44-methylgambier-one and gambierone, and one isolate produced ciguatoxins, the cause of Ciguatera Poisoning. An Ostreopsis tairoto isolate, as analysed by the oxidative cleavage method, produced a palytoxin (PLTX)-like amine oxidation fragment, but when analysed for PLTX-like analogues using a new intact method none were detected indicating an 'unknown' PLTX-like compound is produced by this isolate. Isolates of O. cf. siamensis (Ostreopsis sp. 9), collected in Northland, were also analysed using the oxidative cleavage method, with the common PLTX-like amine fragment and the amide fragment corresponding to bishomoPLTX detected in all isolates. Again, the intact method indicated no detections in the isolates, again suggesting an unknown compound was being pro-duced by these isolates. Prorocentrum hoffmannianum isolates produced okadaic acid (OA) and isoDTX-1 and P. lima isolates produced OA, DTX-1, and isoDTX-1. It is expected that new species of potentially harmful, benthic dinoflagellates will continue to be recorded in Aotearoa New Zealand and the results from Rangita over bar hua provide a guide to the HAB species to expect in sub-tropical Northland as the oceans continue to warm.

Automated summary

The study reveals that temperatures and temperature anomalies are increasing in the sub-tropical regions of Aotearoa New Zealand, potentially impacting harmful algal bloom events. New species of dinoflagellates have been identified, and it is predicted that they may produce more toxins or pose greater threats to marine animals in future climate conditions.