ABSTRACT: Pearl farming lagoons are economically important, yet poorly studied ecosystems in French Polynesia. This paper describes a study conducted in 2016 in Takaroa (Tuamotu Archipelago), an atoll recurrently affected by harmful algal bloom (HAB) events. The objectives were to gain insight into phytoplankton community composition, identify the main bloom-forming species and investigate their potential for toxicity. A mesocosm approach was used to assess the response of phytoplankton communities to 3 nutrient treatments: Conway with Si, Si-depleted f/2 and a commercial N-P fertilizer. In total, 87 morpho-species were described from Takaroa lagoon, with dinoflagellates as the most diverse group. Diatoms (Extubocellulus sp., Cylindrotheca closterium, Nitzschia spp.), dinoflagellates (Gymnodinium spp., Heterocapsa spp.) and flagellates (Cryptomonas sp., Pyraminonas spp.) were among the major bloom-forming species identified. Most markedly, Extubocellulus sp., a diatom never reported from French Polynesia before, was able to bloom even in Si-poor environments. Additionally, in vitro cultures of 12 bloom-forming strains were successfully established and tested for their toxicity. Preliminary results suggest that 9 strains, including dinoflagellates (Prorocentrum lima, Amphidinium spp., Heterocapsa sp.), Pyraminonadales (Pyramimonas sp.) and cryptophytes (Cryptomonas sp.), are the likely producers of cyclic imine neurotoxins and toxins acting on voltage-gated sodium channels. The contribution of these toxins to the mortality events previously reported in Takaroa lagoon is further discussed. Overall, this study highlights the relevance of a mesocosm approach which can be applied to other understudied atolls of French Polynesia recurrently threatened by HABs.

中文翻译：

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塔卡罗阿泻湖（法属波利尼西亚图阿莫图）的藻类形成物种的多样性和毒性潜力：田间和中观研究

摘要：珍珠养殖泻湖在经济上很重要，但在法属波利尼西亚的生态系统研究不足。本文描述了一项于2016年在塔卡洛阿（Tuamotu群岛）进行的研究，该环礁经常受到有害藻华（HAB）事件的影响。目的是深入了解浮游植物群落组成，确定主要的水华形成物种并研究其潜在毒性。中观方法用于评估浮游植物群落对3种养分处理的响应：Conway与Si，贫Si的f / 2和商业NP肥料。总共从塔卡罗阿泻湖中描述了87个形态物种，其中鞭毛藻是最多样化的物种。硅藻（Extubocellulus sp。，Cylindrotheca closterium，Nitzschiasno。spp。），鞭毛虫（Gymnodinium spp。，Heterocapsa spp。）和鞭毛虫（Cryptomonas sp。，Pyraminonas spp。）是确定的主要开花形成物种。最明显的是，Extubocellulus sp。，一种以前从未从法属波利尼西亚得到的硅藻，即使在贫硅环境中也能开花。另外，成功地建立了12个形成花的菌株的体外培养物并测试了它们的毒性。初步结果表明，有9种菌株，其中包括鞭毛藻（Prorocentrum lima，Amphidinium spp。，Heterocapsa sp。），Pyraminonadales（Pyramimonas）。）和隐藻类（Cryptomonas sp。），可能是环状亚胺神经毒素和作用于电压门控钠通道的毒素的产生者。这些毒素对先前在塔卡罗阿泻湖中报告的死亡事件的贡献将进一步讨论。总体而言，这项研究强调了中观方法的相关性，该方法可应用于法布利尼西亚其他受到研究不足的环礁，这些环礁经常受到HAB的威胁。