The genus Gambierdiscus produces an array of bioactive hydrophilic and lipophilic secondary metabolites that range in mode of action and toxicity. In this study, the metabolite fingerprint was mapped for thirteen Gambierdiscus, five Coolia and two Fukuyoa species (34 isolates) by assessing the production of 56 characterised secondary metabolites. Gambierdiscus polynesiensis was the only species to produce Pacific-ciguatoxin-3B (P-CTX3B), P-CTX3C, iso-P-CTX3B/C, P-CTX4A, P-CTX4B and iso-P-CTX4A/B. G. australes produced maitotoxin-1 (MTX-1) and MTX-5, G. cheloniae produced MTX-6 and G. honu produced MTX-7. Ubiquitous production of 44-methylgambierone was observed amongst all the Gambierdiscus isolates, with nine species also producing gambierone. Additional gambierone analogues, including anhydrogambierone (tentatively described herein), were also detected in all Gambierdiscus species, two Coolia and two Fukuyoa species. Gambieroxide was detected in G. lewisii and G. pacificus and gambieric acid A was detected in ten Gambierdiscus species, with G. australes (CAWD381) being the only isolate to produce gambieric acids A–D. This study has demonstrated that the isolates tested to date produce the known CTXs or MTXs, but not both, and highlighted several species that produced ‘unknown’ compounds displaying characteristics of cyclic polyethers, which will be the focus of future compound discovery efforts.

Marine heatwaves (MHWs) are increasing globally, including around Aotearoa New Zealand (NZ), where the Tasman Sea is a recognised hotspot. Harmful algal blooms (HABs) represent an additional climate-linked stressor, with species such as the paralytic shellfish toxin (PST) producing dinoflagellate Alexandrium pacificum becoming more frequent with ocean warming, stratification, and nutrient enrichment. In the Marlborough Sounds-NZ's largest green-lipped mussel (GLM, Perna canaliculus) farming area-A. pacificum blooms now coincide with MHWs. This study exposed subadult GLM to two temperatures-17 °C (control) and 22 °C (peak MHW temperature)-and either PST-producing A. pacificum or non-PST-producing Alexandrium minutum combined with a control diet for two weeks. Physiological and molecular endpoints measured included PST accumulation, global DNA methylation in gills, immune responses, lipid profiles, and tissue pathology. Peak MHW-exposed mussels had depleted glycogen reserves, suggesting increased metabolic demand, and accumulated 1.8X less PSTs than mussels at 17 °C, a potentially favourable finding for aquaculture. At 17 °C, A. pacificum exposure induced greater hemocyte mortality and diapedesis compared to mussels at 22 °C, indicating enhanced immune activation but more immune cell death. Mussels at 22 °C displayed a dampened immune response relative to those at 17 °C based on hemocyte responses and histological analyses. DNA methylation in gill tissue was 1.7X higher at 22 °C, suggesting possible epigenetic regulation of responses. These findings highlight the importance of considering both independent and interactive effects of MHWs and HABs. While temperature influenced metabolic and epigenetic responses, Alexandrium exposure shaped outcomes in immune performance and toxin accumulation.

Ciguatera poisoning (CP) is caused by the consumption of marine products contaminated with ciguatoxins (CTXs) produced by dinoflagellates of the genus Gambierdiscus. Analytical methods for CTXs, involving the extraction/purification of trace quantities of CTXs from complex matrices, are numerous in the literature. However, little information on their effectiveness for nonpolar CTXs is available, yet these congeners, contributing to the risk of CP, are required for the establishment of effective food safety monitoring programs. An evaluation of six extraction/purification protocols, performed with CTX3C spiked on fish flesh and a neuroblastoma cell-based assay (CBA-N2a), revealed recoveries from 6 to 45%. This led to the development of an optimized 3-day protocol designed for a large number of samples, with CTX1B and CTX3C eluting in a single fraction and showing recoveries of 73% and 70%, respectively. In addition, a reduction in adverse matrix effects in the CBA-N2a analyses was demonstrated with naturally contaminated specimens, increasing the sensitivity of the method, which now meets the very low guidance level recommended by international agencies. However, efforts are still required to reduce the signal suppression observed in LC-MS/MS analysis. This optimized protocol contributes to the technological advancement of detection methods, promoting food safety and improving CP risk assessment in marine products.

The giant moray eel (GME; Gymnothorax javanicus) is an important marine species that plays a key ecological role in reef systems and is a valued food source for indigenous communities. However, it is well-known that GMEs pose a food safety risk due to their ability to accumulate high levels of ciguatoxins (CTXs), the toxins known to cause ciguatera poisoning. This study assessed the age, CTX levels, elemental composition, and nutritional profile of seven GME specimens collected from Muri Lagoon, Rarotonga (Cook Islands), representing the most detailed compositional investigation on this species. Age was determined for the three largest specimens, with the oldest being 39 years old. All specimens contained ciguatoxins, with Type I (CTX4A derivatives), Type II (CTX3C derivatives), algal-ciguatoxins, and biotransformed metabolites being detected. There was a higher CTX content in the liver samples compared to flesh samples, with the longest–heaviest specimen containing the highest levels. The CTX1B level observed in flesh samples of all seven eel specimens exceeded the recommended safe guidance level proposed by the USFDA. A similar ciguatoxin profile was observed across flesh sections, with the belly flap or top loin containing the highest levels of CTXs in most specimens. No bioactive metabolites produced by co-occurring harmful microalgae, including regulated shellfish toxins, were detected. Elemental analysis determined the presence of 21 elements, including arsenic, low levels of mercury, and the volcanic elements rubidium and strontium. Nutritionally, the GMEs were shown to be a lean protein source; however, due to the ubiquitous bioaccumulation of CTXs, they pose a food safety risk to consumers.

Ciguatera poisoning (CP) is the most prevalent marine toxin illness globally and disproportionately affects people from circumtropical regions due to the occurrence of the causative microalgae, Gambierdiscus. Increased reports of CP cases globally are linked to changing ocean temperatures, localized outbreaks in new regions and importation of ciguatoxin-contaminated fish into non-endemic regions. Gambierdiscus spp. produce several classes of bioactive polyether metabolites in addition to ciguatoxins, including gambierones, maitotoxins, gambieroxide, gambierol and gambieric acids. The role of these additional metabolites in CP remains unclear. In this study, non-targeted analysis using LC-HRMS was used to examine gambieroxide profiles in Gambierdiscus and Fukuyoa species. Initially purified gambieroxide was compared with a tentatively assigned gambieroxide analogue detected in G. pacificus and G. lewisii. The method was then used to characterize gambieroxide-like analogue profiles in the extracts of thirteen Gambierdiscus and two Fukuyoa species, with over thirty different analogues detected based on characteristic mass spectral fragmentation patterns in both positive and negative ionization modes. With few prior reports of these compounds, their detection across various species and strains provides valuable insight into the diversity of polyether compounds produced by Gambierdiscus and Fukuyoa. Future work will focus on understanding the significance of these gambieroxide-like analogues in CP.