A new species of Gambierdiscus (Dinophyceae) from the south-west Pacific: Gambierdiscus honu sp. nov.

Two isolates of a new tropical, epiphytic dinoflagellate species, Gambierdiscus honu sp. nov., were obtained from macroalgae sampled in Rarotonga, Cook Islands, and from North Meyer Island, Kermadec Islands. Gambierdiscus honu sp. nov. had the common Gambierdiscus Kofoidian plate formula: Po, 3', 6″, 6C?, 6 or 7S, 5‴, 1p and 2⁗. The characteristic morphological features of this species were its relatively small short dorsoventral length and width and the shape of individual plates, in particular the combination of the hatchet-shaped 2' and pentagonal 3' plates and the length to width ratio of the antapical 1p plate. The combination of these characteristics plus the smooth thecal surface and equal sized 1⁗ and 2⁗ plates differentiated this species from other Gambierdiscus species. The phylogenetic analyses supported the unique description. Both isolates of G. honu produced the putative maitotoxin (MTX)-3 analogue, but neither produced ciguatoxin (CTX) or MTX. Extracts of G. honu were shown to be highly toxic to mice by intraperitoneal injection (0.2mg/kg), although less toxic by gavage. It is possible that toxins other than putative MTX-3 are produced.

A new Gambierdiscus species (Dinophyceae) from Rarotonga, Cook Islands: Gambierdiscus cheloniae sp. nov.

Ciguatera fish poisoning (CFP) has been reported for many years in Rarotonga, Cook Islands, and has had the world's highest reported incidence of this illness for the last 20 years. Following intensive sampling to understand the distribution of the causative organisms of CFP, an undescribed Gambierdiscus species was isolated from the Rarotongan lagoon. Gambierdiscus cheloniae sp. nov. has the common Gambierdiscus Kofoidian plate formula (except for a variability in the number of precingular plates in aberrant cells): Po, 3', 6″ (7″), 6C?, 6 or 7S, 5'″, 1p and 2″″. The 2' plate is hatchet shaped and the dorsal end of 1p is pointed and the relatively narrow 1p plate. Morphologically G. cheloniae is similar to the genetically closely related species G. pacificus, G. toxicus and G. belizeanus, although smaller (depth and length) than G. toxicus. The apical pore plate varies from those of G. belizeanus and G. pacificus, which are shorter and narrower, and from G. toxicus, which is larger. G. cheloniae also differs from G. pacificus in the shape of the 2' plate. The description of this new species is supported by phylogenetic analyses using three different gene regions. G. cheloniae produced the putative maitotoxin-3 analogue, MTX-3, but neither maitotoxin or monitored ciguatoxin. Extracts of G. cheloniae were shown to be highly toxic to mice by intraperitoneal (i.p.) injection, although they were less toxic by gavage. It is possible that this species produces toxins other than putative MTX-3.

The effects of natural disturbances, reef state, and herbivorous fish densities on ciguatera poisoning in Rarotonga, southern Cook Islands.

Ciguatera poisoning is a critical public-health issue among Pacific island nations. Accurately predicting ciguatera outbreaks has become a priority, particularly in Rarotonga in the southern Cook Islands, which has reported the highest incidence of ciguatera poisoning globally. Since 2006, however, cases of ciguatera poisoning have declined, and in 2011 ciguatera cases were the lowest in nearly 20 years. Here we examined the relationships between cases of ciguatera poisoning, from 1994 to 2011, and: (i) coral cover, used as a proxy of reef state, (ii) the densities of herbivorous fishes, and (iii) reef disturbances. We found that coral cover was not a good predictor of cases of ciguatera poisoning, but high densities of the herbivorous fish Ctenochaetus striatus and reef disturbances were both strong predictors of ciguatera poisoning. Yet these two predictors were correlated, because the densities of C. striatus increased only after major cyclones had disturbed the reefs. Since 2006, the number of cyclones has decreased considerably in Rarotonga, because of the climatic shift toward the negative phase of the Pacific Decadal Oscillation. We suggest that fewer cyclones have led to decreases in both the densities of C. striatus and of the number of reported cases of ciguatera poisoning in Rarotonga.

The use of cellular diagnostics for identifying sub-lethal stress in reef corals.

Coral reefs throughout the world are exhibiting documented declines in coral cover and species diversity, which have been linked to anthropogenic stressors including land-based sources of pollution. Reductions in coastal water and substratum quality are affecting coral survivorship, reproduction and recruitment, and hence, the persistence of coral reefs. One major obstacle in effectively addressing these declines is the lack of tools that can identify cause-and-effect relationships between stressors and specific coral reef losses, while a second problem is the inability to measure the efficacy of mitigation efforts in a timely fashion. We examined corals from six coral reefs on Guam, Mariana Islands, which were being affected by different environmental stressors (e.g. PAH's, pesticides, PCB's and sedimentation). Cellular diagnostic analysis differentiated the cellular-physiological condition of these corals. Examination of protein expression provided insight into their homeostatic responses to chemical and physical stressors in exposed corals prior to outright mortality, providing improved opportunities for developing locally-based management responses. This approach adds critically needed tools for addressing the effects of multiple stressors on corals and will allow researchers to move beyond present assessment and monitoring techniques that simply document the loss of coral abundance and diversity.