Climate warming can change species performance and ecological interactions, which alter the energy flow in aquatic ecosystems. Here, we set microcosms to analyse how warming and predator affect the functional responses of three subtropical cladocerans (Ceriodaphnia silvestrii, Daphnia laevis, and Simocephalus serrulatus). Predator treatments included young-fish presence, young-fish absence, and fish chemical cues. Warming treatments included a control at 22 °C and others at + 2 °C and + 4 °C. We expected that warming would increase cladocerans’ growth, reproduction, and feeding rates by metabolic demands, which also would increase the predation of fish on cladocerans and cladocerans on phytoplankton. The effects of warming and predator on cladocerans functional responses (secondary productivity and grazing rates) were tested through Linear Mixed Models, Generalized Linear Model, and Piecewise Structural Equation Modeling (piecewise SEM). Cladocerans' secondary productivity and grazing were primarily dictated by fish predation and chemical cues, but warming also reduced the grazing of cladocerans on phytoplankton. Warming and predation differently affected the secondary productivity of species depending on their body size, S. serrulatus (the largest-bodied) had reduced rates at high temperatures, D. laevis (the medium-bodied) in young-fish presence, and C. silvestrii (the smallest-bodied) at both treatments. The three species increased secondary productivity in response to fish chemical cues. Our results clarify the unique and combined effect of global warming and predator on the energy availability inside freshwater food-webs. Warming and predator have the potential to reduce cladocerans' secondary productivity and increase primary productivity in subtropical ecosystems.

气候变暖会改变物种表现和生态相互作用，从而改变水生生态系统中的能量流动。在这里，我们设置微观世界来分析变暖和捕食者如何影响三种亚热带枝角类动物（Ceriodaphnia silvestrii、Daphnia laevis和Simocephalus serrulatus）的功能反应。）。捕食者处理包括幼鱼存在、幼鱼缺失和鱼类化学线索。加温处理包括 22°C 的控制和 +2°C 和 +4°C 的其他控制。我们预计气候变暖会通过代谢需求增加枝角类动物的生长、繁殖和摄食率，这也会增加鱼类对枝角类动物和枝角类动物对浮游植物的捕食。通过线性混合模型、广义线性模型和分段结构方程建模（分段 SEM）测试了变暖和捕食者对枝角类功能反应（二次生产力和放牧率）的影响。枝角类动物的二次生产力和放牧主要由鱼类捕食和化学线索决定，但变暖也减少了枝角类动物对浮游植物的放牧。S. serrulatus（体型最大的）在高温下发生率降低，D. laevis（中等体型）在幼鱼存在时和C. silvestrii（体型最小）在两种处理中均降低。这三个物种响应鱼类化学线索增加了二次生产力。我们的结果阐明了全球变暖和捕食者对淡水食物网内能量可用性的独特和综合影响。变暖和捕食者有可能降低枝角类动物的次级生产力并提高亚热带生态系统的初级生产力。