ABSTRACT: The nuisance raphidophyte Gonyostomum semen (Ehrenberg) Diesing blooms in lakes and is known to produce a mucilage which can cause human skin irritation. Parameters such as water temperature, iron and high dissolved organic matter loads are shown to be important drivers in temperate regions. However, the causes of blooms in warmer latitudes are less well understood. Over a 6 mo study period, we used field monitoring and a nutrient addition experiment within a water reservoir to examine the role of nutrients in promoting G. semen growth. Early in the study, an inflow event delivered nutrients which increased dissolved inorganic nitrogen (DIN) concentrations 2-fold and filterable reactive phosphorus (FRP = phosphate) 4-fold. This event shifted the phytoplankton community from a mixed community to one dominated by G. semen. Two months after the inflow event, the effect of nutrients in promoting G. semen was confirmed with a nutrient addition experiment. Total biovolumes of this species across the study were strongly predicted by FRP and nitrate + nitrite concentrations. G. semen biovolumes also decreased as ratios of total nitrogen (TN):total phosphorus (TP) and DIN:FRP increased, highlighting the importance of P inputs. The stable isotope tracer ¹⁵N-nitrate was also used to trace N through the G. semen-dominated phytoplankton community. The tracer rapidly cycled through the G. semen-dominated phytoplankton community in 1-2 d, settled and remineralized, providing an ongoing source of DIN for maintaining blooms. Overall, the results highlight the importance of FRP, and to a lesser extent nitrate, in promoting blooms of this nuisance species.

中文翻译：

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营养物质在亚热带水库中促进讨厌的水生藻类物种Gonyostomum精液开花的作用

摘要：令人讨厌的蝴蝶藻植物精液（Ehrenberg）死于湖泊中的花朵，已知会产生黏液，可引起人体皮肤刺激。在温带地区，诸如水温，铁和高溶解有机物负荷等参数被证明是重要的驱动因素。但是，对纬度较高的地区开花的原因了解得很少。在6个月的研究期内，我们使用了田间监测和水库中的养分添加实验，以研究养分在促进精液生长方面的作用。在研究的早期，流入事件释放出的营养物质使溶解的无机氮（DIN）浓度增加了2倍，可过滤的活性磷（FRP =磷酸盐）则增加了4倍。这一事件使浮游植物群落从混合群落转变为以G为主的群落。精液。流入事件后两个月，通过营养添加实验确认了营养对促进精液的作用。通过FRP和硝酸盐+亚硝酸盐浓度强烈预测了整个研究过程中该物种的总生物量。随着总氮（TN）：总磷（TP）和DIN：FRP比例的增加，精液G.精液的生物量也减少了，这突出了P输入的重要性。稳定同位素示踪剂¹⁵硝酸N也被用来通过精液支配的浮游植物群落来追踪N。示踪剂在1-2 d内迅速循环到精液中以浮游植物为主的群落中，使其沉降并再矿化，从而为保持花开提供了持续的DIN来源。总的来说，这些结果突出了FRP的重要性，而在较小程度上，硝酸盐对于促进这种有害物种的开花非常重要。