Horizontal and vertical distribution of Gambierdiscus spp. (Dinophyceae) including novel phylotypes in Japan identified by 18S rDNA metabarcoding

Funaki, Hiroshi; Gaonkar, Chetan C.; Kataoka, Takafumi; Nishimura, Tomohiro; Tanaka, Kosuke; Yanagida, Ippei; Abe, Shouta; Yamaguchi, Haruo; Nagasaki, Keisuke; Adachi, Masao

doi:10.1016/j.hal.2021.102163

Cited by 7 publications

(1 citation statement)

References 83 publications

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“…Conditions that promote the growth of Gambierdiscus populations are likely not the same as those that promote turf algae productivity, as turf communities show a general lack of photo-inhibition that likely underpins their high productivity at the shallowest water depths, with most production reliant on the apical portion of filaments, i.e., above the sediment layer and exposed to higher water motion and light [ 118 ]. In contrast, Gambierdiscus species appear to be well adapted to low light conditions [ 75 , 120 , 121 ], with the highest population densities at around the 10 m depth on screens in the Canary Islands [ 73 ], although Loeffler et al [ 69 ] found no significant differences between populations at 10 m and 23 m depths at sites in the Caribbean. However, what is often missing from environmental studies on Gambierdiscus populations is the consideration that benthic dinoflagellate populations may also be controlled by herbivory and that the populations measured at any one time are likely the result of interactions between growth rates that vary with environmental gradients, offset against gradients of herbivory.…”

Section: Resultsmentioning

confidence: 99%

Model of the Origin of a Ciguatoxic Grouper (Plectropomus leopardus)

Holmes

Lewis

2023

Toxins

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Published data were used to model the transfer of ciguatoxins (CTX) across three trophic levels of a marine food chain on the Great Barrier Reef (GBR), Australia, to produce a mildly toxic common coral trout (Plectropomus leopardus), one of the most targeted food fishes on the GBR. Our model generated a 1.6 kg grouper with a flesh concentration of 0.1 µg/kg of Pacific-ciguatoxin-1 (P-CTX-1 = CTX1B) from 1.1 to 4.3 µg of P-CTX-1 equivalents (eq.) entering the food chain from 0.7 to 2.7 million benthic dinoflagellates (Gambierdiscus sp.) producing 1.6 pg/cell of the P-CTX-1 precursor, P-CTX-4B (CTX4B). We simulated the food chain transfer of ciguatoxins via surgeonfishes by modelling Ctenochaetus striatus feeding on turf algae. A C. striatus feeding on ≥1000 Gambierdiscus/cm2 of turf algae accumulates sufficient toxin in <2 days that when preyed on, produces a 1.6 kg common coral trout with a flesh concentration of 0.1 µg/kg P-CTX-1. Our model shows that even transient blooms of highly ciguatoxic Gambierdiscus can generate ciguateric fishes. In contrast, sparse cell densities of ≤10 Gambierdiscus/cm2 are unlikely to pose a significant risk, at least in areas where the P-CTX-1 family of ciguatoxins predominate. The ciguatera risk from intermediate Gambierdiscus densities (~100 cells/cm2) is more difficult to assess, as it requires feeding times for surgeonfish (~4–14 days) that overlap with turnover rates of turf algae that are grazed by herbivorous fishes, at least in regions such as the GBR, where stocks of herbivorous fishes are not impacted by fishing. We use our model to explore how the duration of ciguatoxic Gambierdiscus blooms, the type of ciguatoxins they produce, and fish feeding behaviours can produce differences in relative toxicities between trophic levels. Our simple model indicates thresholds for the design of risk and mitigation strategies for ciguatera and the variables that can be manipulated to explore alternate scenarios for the accumulation and transfer of P-CTX-1 analogues through marine food chains and, potentially, for other ciguatoxins in other regions, as more data become available.

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