Ciguatera Poisoning (CP) is a widespread and complex poisoning syndrome caused by the consumption of fish or invertebrates contaminated with a suite of potent neurotoxins collectively known as ciguatoxins (CTXs), which are produced by certain benthic dinoflagellates species in the genera Gambierdiscus and Fukuyoa. Due to the complex nature of this HAB problem, along with a poor understanding of toxin production and entry in the coral reef food web, the development of monitoring, management, and forecasting approaches for CP has lagged behind those available for other HAB syndromes. Over the past two decades, renewed research on the taxonomy, physiology, and toxicology of CP-causing dinoflagellates has advanced our understanding of the species diversity that exists within these genera, including identification of highly toxic species (so called “superbugs”) that likely contribute disproportionately to ciguatoxins entering coral reef food webs. The recent development of approaches for molecular analysis of field samples now provide the means to investigate in situ community composition, enabling characterization of spatio-temporal species dynamics, linkages between toxic species abundance and toxin flux, and the risk of ciguatoxin prevalence in fish. In this study we used species-specific fluorescent in situ hybridization (FISH) probes to investigate Gambierdiscus species composition and dynamics in St. Thomas (USVI) and the Florida Keys (USA) over multiple years (2018–2020). Within each location, samples were collected seasonally from several sites comprising varying depths, habitats, and algal substrates to characterize community structure over small spatial scales and across different host macrophytes. This approach enabled the quantitative determination of communities over spatiotemporal gradients, as well as the selective enumeration of species known to exhibit high toxicity, such as Gambierdiscus silvae. The investigation found differing community structure between St. Thomas and Florida Keys sites, driven in part by differences in the distribution of toxin-producing species G. silvae and G. belizeanus, which were present throughout sampling sites in St. Thomas but scarce or absent in the Florida Keys. This finding is significant given the high toxicity of G. silvae, and may help explain differences in fish toxicity and CP incidence between St. Thomas and Florida. Intrasite comparisons along a depth gradient found higher concentrations of Gambierdiscus spp. at deeper locations. Among the macrophytes sampled, Dictyota may be a likely vector for toxin transfer based on their widespread distribution, apparent colonization by G. silvae, and palatability to at least some herbivore grazers. Given its ubiquity throughout both study regions and sites, this taxa may also serve as a refuge, accumulating high concentrations of Gambierdiscus and other benthic dinoflagellates, which in turn can serve as source populations for highly palatable and ephemeral habitats nearby, such as turf algae. These studies further demonstrate the successful application of FISH probes in examining biogeographic structuring of Gambierdiscus communities, targeting individual toxin-producing species, and characterizing species-level dynamics that are needed to describe and model ecological drivers of species abundance and toxicity.

雪卡中毒 (CP) 是一种广泛而复杂的中毒综合征，由食用被一系列强效神经毒素（统称为雪卡毒素 (CTX)）污染的鱼类或无脊椎动物引起，这些毒素是由甘比尔属和福叶甲属的某些底栖甲藻产生的。由于该 HAB 问题的复杂性，以及对毒素产生和进入珊瑚礁食物网的了解不足，CP 的监测、管理和预测方法的开发落后于其他 HAB 综合征的可用方法。在过去的二十年中，对引起 CP 的甲藻的分类学、生理学和毒理学的重新研究增进了我们对这些属中存在的物种多样性的理解，包括鉴定可能具有剧毒的物种（所谓的“超级细菌”）。导致雪卡毒素进入珊瑚礁食物网。最近开发的野外样品分子分析方法现在提供了研究原位群落组成的方法，能够表征时空物种动态、有毒物种丰度和毒素通量之间的联系以及鱼类中雪卡毒素流行的风险。在这项研究中，我们使用物种特异性荧光原位杂交 (FISH) 探针来研究多年来（2018-2020 年）圣托马斯岛（美属维尔京群岛）和佛罗里达群岛（美国）的甘比尔鞭毛虫物种组成和动态。在每个地点，从不同深度、栖息地和藻类基质的多个地点季节性收集样本，以表征小空间尺度和不同寄主大型植物的群落结构。这种方法能够定量测定时空梯度上的群落，以及选择性计数已知表现出高毒性的物种，例如Gambierdiscus silvae。调查发现，圣托马斯和佛罗里达群岛采样点之间存在不同的群落结构，部分原因是产生毒素的物种G. silvae和G. belizeanus 的分布差异，这些物种存在于圣托马斯的整个采样点，但很少或不存在在佛罗里达群岛。鉴于G. silvae的高毒性，这一发现具有重要意义，并且可能有助于解释圣托马斯和佛罗里达州之间鱼类毒性和 CP 发生率的差异。沿深度梯度的站点内比较发现甘比尔盘属的浓度更高。在更深的位置。在采样的大型植物中，网皮藻可能是毒素转移的可能载体，因为它们分布广泛，且明显被G. silvae定植，以及至少对一些食草动物的适口性。鉴于其在研究区域和地点的普遍存在，该类群也可能作为避难所，积累高浓度的甘比尔鞭毛虫和其他底栖甲藻，而这些甲藻反过来又可以作为附近高度适口且短暂的栖息地（例如草皮藻）的来源种群。这些研究进一步证明了 FISH 探针在检查Gambierdiscus群落的生物地理结构、针对单个产毒物种以及描述物种丰度和毒性的生态驱动因素所需的物种水平动态特征方面的成功应用。