Abstract The effects of food quality and food quantity on crustacean zooplankton’s feeding rate have been analyzed in the present study. In two experiments, we studied the clearance rates (CRs) of Daphnia pulex on different algal diets (Scenedesmus obliquus, nontoxic Microcystis sp. PCC7806 and Anabeana flos-aquae) varying in carbon to phosphorus (C:P) ratios and quantities (concentrations). In order to investigate the effects of different algal diets on the feeding of cladocerans, the mixture of S. obliquus, Microcystis sp. PCC7806 and A. flos-aquae was also fed to D. pulex during a 72-h period. Our results showed: (1) D. pulex had different clearance rates from the three mono-specific P-rich algal diets, while no significant difference among clearance rates was observed among the three mono-specific P-poor algal diets; (2) D. pulex increased its clearance rates when it fed on mono-specific P-poor S. obliquus and A. flos-aquae, while a P-poor mixture of M. aeruginosa and A. flos-aquae reduced the clearance rate; (3) A U-shaped quadratic function provided a good fit to the clearance rate and C:P ratios because the clearance rate of D. pulex in both low and high C:P categories were significantly higher than in the moderate C:P category (C:P value = 219). Our results demonstrated that filaments and C:P ratios of algae strongly influence the feeding of crustacean zooplankton. ‘Compensatory feeding’ occurred in the mono-specific, P-poor algal diets but not in the mixed diets. Moreover, the clearance rate of zooplankton was the lowest in the moderate P stoichiometric category. Our experiments suggest that the morphology and C:P ratios of algal diets have important effects on the feeding of Daphnia, and the P stoichiometric characteristics in mixed diets may play an important role in the feeding of large-sized cladocerans.

中文翻译：

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高、低C:P食物对溞采食的影响

摘要 本研究分析了食物质量和食物数量对浮游甲壳类动物摄食率的影响。在两个实验中，我们研究了水溞在不同藻类饲料（斜纹夜蛾、无毒微囊藻 PCC7806 和 Anabeana flos-aquae）上的清除率 (CR)，其碳磷 (C:P) 比率和数量（浓度）不同. 为了研究不同藻类饮食对枝角类动物摄食的影响，S.obliquus、Microcystis sp. 的混合物。PCC7806 和 A. flos-aquae 也在 72 小时内喂给 D. pulex。我们的结果表明：（1）D. pulex 对三种单一特异性富磷藻类饲料的清除率不同，而三种单一特异性贫磷藻类饲料的清除率没有显着差异；(2) D。pulex 以单一特异性 P-poor S.obliquus 和 A. flos-aquae 为食时提高了其清除率，而 M. aeruginosa 和 A. flos-aquae 的贫磷混合物降低了清除率；(3) U 形二次函数对清除率和 C:P 比率提供了很好的拟合，因为低和高 C:P 类别中 D. pulex 的清除率显着高于中等 C:P 类别（C:P 值 = 219）。我们的结果表明，藻类的细丝和 C:P 比率强烈影响甲壳类浮游动物的摄食。“补偿性喂养”发生在单一的、贫磷的藻类饮食中，但没有发生在混合饮食中。此外，浮游动物的清除率在中等 P 化学计量类别中最低。我们的实验表明形态和 C：