The transfer of energy through zooplankton grazing on phytoplankton is one of the most important interactions in aquatic ecosystems, yet the role of hydrodynamic forces is not fully understood. Factors that influence these interactions include algal size and shape and the interactions between grazer and alga dictated by hydrodynamic forces. Hydrodynamic forcing lead to unimodal relationships in grazer clearance rates (CR) because water motion and turbulence increases encounters but interferes with feeding at high levels. We expect higher CR on small algae due to increased encounter rates caused by vorticity generated in a horizontally oriented rotating cylinder to model increasing turbulence, whereas longer cells, tumbling in the flow, may be more difficult to handle. Ultimately, we expect that increased vorticity will interfere with zooplankton swimming. The CR of Daphnia magna followed the unimodal trend, with higher CR on the small, spherical Chlorella vulgaris than on larger, elongated, and colonial Scenedesmus quadricauda. This was likely due to lower handling time and higher concentration of the smaller cells in the feeding radius around D. magna. The normal hop‐sink swimming behavior of the Daphnia was affected by increasing vorticity; hop frequency decreased, displacement increased, and there was a loss of vertical orientation. This pattern in feeding and swimming were predicted by vorticity. These results for Daphnia differ from those obtained for copepods, which do not respond to vorticity. Given the importance of vorticity in nature, it is relevant to examine grazer feeding interactions under ecologically relevant hydrodynamic conditions.

中文翻译：

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涡度对淡水食草动物摄食的影响


通过浮游动物吃浮游植物进行的能量转移是水生生态系统中最重要的相互作用之一，但水动力的作用尚未完全了解。影响这些相互作用的因素包括藻类的大小和形状以及水动力决定的食草动物和藻类之间的相互作用。水动力强迫导致食草清除率（CR）的单峰关系，因为水运动和湍流增加了相遇，但干扰了高水平的进食。我们预计小藻类的 CR 会更高，因为水平旋转圆柱体中产生的涡流会增加遇到率，以模拟不断增加的湍流，而在流动中翻滚的较长细胞可能更难以处理。最终，我们预计涡度的增加会干扰浮游动物的游泳。大型溞的 CR 遵循单峰趋势，小型球形小球藻的 CR 高于较大的、细长的、群居的四尾栅藻。这可能是由于处理时间较短和 D. magna 周围进食半径内较小细胞的浓度较高。水蚤正常的跳跃下沉游泳行为受到涡度增加的影响。跳跃频率降低，位移增加，垂直方向丧失。这种进食和游泳的模式是通过涡度预测的。水蚤的这些结果与桡足类的结果不同，后者对涡度没有反应。鉴于涡度在自然界中的重要性，在生态相关的水动力条件下检查食草动物的摄食相互作用是相关的。