Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
PLoS One. 2013 May 7;8(5):e62557. doi: 10.1371/journal.pone.0062557. Print 2013.
The large bloom-forming flagellate Gonyostomum semen has been hypothesized to be inedible to naturally occurring zooplankton due to its large cell size and ejection of long slimy threads (trichocysts) induced by physical stimulation. In a grazing experiment using radiolabelled algae and zooplankton collected from lakes with recurring blooms of G. semen and lakes that rarely experience blooms, we found that Eudiaptomus gracilis and Holopedium gibberum fed on G. semen at high rates, whereas Daphnia cristata and Ceriodaphnia spp. did not. Grazing rates of E. gracilis were similar between bloom-lakes and lakes with low biomass of G. semen, indicating that the ability to feed on G. semen was not a result of local adaptation. The high grazing rates of two of the taxa in our experiment imply that some of the nutrients and energy taken up by G. semen can be transferred directly to higher trophic levels, although the predominance of small cladocerans during blooms may limit the importance of G. semen as a food resource. Based on grazing rates and previous observations on abundances of E. gracilis and H. gibberum, we conclude that there is a potential for grazer control of G. semen and discuss why blooms of G. semen still occur.
大型有鞭毛的赤潮生物鱼腥藻（Gonyostomum semen）由于其细胞体积大，并且受到物理刺激时会排出长长的粘性丝（刺丝囊），因此被假设为不能被天然浮游动物食用。在一项使用放射性标记藻类和浮游动物的摄食实验中，这些浮游动物是从鱼腥藻反复爆发赤潮的湖泊和很少爆发赤潮的湖泊中收集的，我们发现，Eudiaptomus gracilis 和 Holopedium gibberum 以很高的速率摄食鱼腥藻，而 Daphnia cristata 和 Ceriodaphnia spp. 则不摄食。E. gracilis 的摄食速率在赤潮湖泊和鱼腥藻生物量低的湖泊之间相似，这表明摄食鱼腥藻的能力不是局部适应的结果。实验中两种生物的高摄食率意味着鱼腥藻摄取的一些营养物质和能量可以直接转移到更高的营养级，尽管在赤潮期间小型桡足类占主导地位可能会限制鱼腥藻作为食物资源的重要性。根据摄食率以及之前对 E. gracilis 和 H. gibberum 丰度的观察，我们得出结论，浮游动物有可能控制鱼腥藻，并讨论为什么鱼腥藻仍会爆发赤潮。
