Growth and epiphytic behavior of three Gambierdiscus species (Dinophyceae) associated with various macroalgal substrates

Gambierdiscus and Fukuyoa species have been identified in Aotearoa/New Zealand’s coastal waters and G. polynesiensis, a known producer of ciguatoxins, has been isolated from Rangitāhua/Kermadec Islands (a New Zealand territory). The warming of the Tasman Sea and the waters around New Zealand’s northern subtropical coastline heighten the risk of Gambierdiscus proliferating in New Zealand. If this occurs, the risk of ciguatera fish poisoning due to consumption of locally caught fish will increase. Research, including the development and testing of sampling methods, molecular assays, and chemical and toxicity tests, will continue. Reliable monitoring strategies are important to manage and mitigate the risk posed by this emerging threat. The research approaches that have been made, many of which will continue, are summarised in this review.

Section: Macroalgae Substratesmentioning

confidence: 89%

Ciguatera Fish Poisoning: The Risk from an Aotearoa/New Zealand Perspective

Rhodes

Smith

Murray

et al. 2020

“…Although, beyond this study, to differentiate, there are multiple aspects where macroalgal abundance and composition might impact Gambierdiscus abundance and ciguatoxin transferability. Specifically, Gambierdiscus-macroalgae host interactions, which can be species-specific, might depend on shading potential, chemical cues, and hostpalatability to higher trophic levels [58][59][60]. Since Gambierdiscus species determination has further developed since this study, future studies could determine if there are particular in situ host associations or macroalgal abundance that favor particularly toxic species/strains and if these associations are linked to the environmental conditions and benthic community compositions that vary between these nearshore and offshore sites.…”

Section: Nearshore Vs Offshore Sitesmentioning

confidence: 99%

Asynchrony of Gambierdiscus spp. Abundance and Toxicity in the U.S. Virgin Islands: Implications for Monitoring and Management of Ciguatera

Liefer

Richlen

Smith

et al. 2021

Ciguatera poisoning (CP) poses a significant threat to ecosystem services and fishery resources in coastal communities. The CP-causative ciguatoxins (CTXs) are produced by benthic dinoflagellates including Gambierdiscus and Fukuyoa spp., and enter reef food webs via grazing on macroalgal substrates. In this study, we report on a 3-year monthly time series in St. Thomas, US Virgin Islands where Gambierdiscus spp. abundance and Caribbean-CTX toxicity in benthic samples were compared to key environmental factors, including temperature, salinity, nutrients, benthic cover, and physical data. We found that peak Gambierdiscus abundance occurred in summer while CTX-specific toxicity peaked in cooler months (Feb–May) when the mean water temperatures were approximately 26–28 °C. These trends were most evident at deeper offshore sites where macroalgal cover was highest year-round. Other environmental parameters were not correlated with the CTX variability observed over time. The asynchrony between Gambierdiscus spp. abundance and toxicity reflects potential differences in toxin cell quotas among Gambierdiscus species with concomitant variability in their abundances throughout the year. These results have significant implications for monitoring and management of benthic harmful algal blooms and highlights potential seasonal and highly-localized pulses in reef toxin loads that may be transferred to higher trophic levels.

“…Growth is dependent on many interacting environmental factors including temperature, light, and nutrients, all of which can vary with depth and aspect on the reef. Mustapa et al [ 270 ] reported growth rates for Malaysian Gambierdiscus isolates growing in culture on turf algae that ranged between ~0.1 to <0.3 divisions/day. Growth rates of 0.1–0.25 divisions/day (i.e., population doubling every 4–10 days) could possibly maintain a Gambierdiscus population on turf algae if, as suggested by Marshell and Mumby [ 263 ] and references therein, that turf algae biomass can be turned over by grazers every 4 to 25 days (especially as reported growth rates for Gambierdiscus are often from experiments trying to produce optimal laboratory growth conditions).…”

Section: A Conceptual Model For Ciguateric Food-chains On the Great Barrier Reefmentioning

confidence: 99%

Critical Review and Conceptual and Quantitative Models for the Transfer and Depuration of Ciguatoxins in Fishes

Holmes

Venables

Lewis

2021

We review and develop conceptual models for the bio-transfer of ciguatoxins in food chains for Platypus Bay and the Great Barrier Reef on the east coast of Australia. Platypus Bay is unique in repeatedly producing ciguateric fishes in Australia, with ciguatoxins produced by benthic dinoflagellates (Gambierdiscus spp.) growing epiphytically on free-living, benthic macroalgae. The Gambierdiscus are consumed by invertebrates living within the macroalgae, which are preyed upon by small carnivorous fishes, which are then preyed upon by Spanish mackerel (Scomberomorus commerson). We hypothesise that Gambierdiscus and/or Fukuyoa species growing on turf algae are the main source of ciguatoxins entering marine food chains to cause ciguatera on the Great Barrier Reef. The abundance of surgeonfish that feed on turf algae may act as a feedback mechanism controlling the flow of ciguatoxins through this marine food chain. If this hypothesis is broadly applicable, then a reduction in herbivory from overharvesting of herbivores could lead to increases in ciguatera by concentrating ciguatoxins through the remaining, smaller population of herbivores. Modelling the dilution of ciguatoxins by somatic growth in Spanish mackerel and coral trout (Plectropomus leopardus) revealed that growth could not significantly reduce the toxicity of fish flesh, except in young fast-growing fishes or legal-sized fishes contaminated with low levels of ciguatoxins. If Spanish mackerel along the east coast of Australia can depurate ciguatoxins, it is most likely with a half-life of ≤1-year. Our review and conceptual models can aid management and research of ciguatera in Australia, and globally.