Stresses imposed by insecticides and predators are possibly the most rigorous filters to which aquatic organisms are exposed in rivers and lakes associated with agricultural lands. However, their interactive effects on zooplankton communities are still unclear. This study elucidated the zooplankton community response to fish predation, the insecticide chlorpyrifos (CLP), and a combination of both factors, using a 30-day mesocosm experiment. The zooplankton assemblage was influenced by fish presence prior to CLP toxicity. Fish predation reduced microcrustacean density leading to a community dominated by microzooplankton (i.e.: rotifers and copepod nauplii). CLP decreased the species richness in treatments with and without fish, yielding an increase in the abundance of bdelloid rotifers, in the genera Lepadella and Trichocerca. The zooplankton:phytoplankton (<20 μm) ratio decreased substantially when the two stressors, fish predation and insecticide toxicity, were combined. Although CLP dissipated relatively rapidly in the aqueous phase and accumulated in sediment and fish tissue, zooplankton richness was unable to recover. A possible explanation for this could be the inhibitory effect of CLP on resting stage hatchings in the sediment. Therefore, the combined effects of fish predation and CLP might influence zooplankton richness, leading to an assemblage dominated by rotifers that appeared to be resistant to both factors, with a limited capability to control phytoplankton growth. Thus, the effects of natural and anthropogenic stressors should be considered together when assessing community dynamics in aquatic ecosystems.

杀虫剂和捕食者施加的压力可能是与农田相关的河流和湖泊中水生生物暴露于其中的最严格的过滤器。但是，它们对浮游动物群落的相互作用影响尚不清楚。这项研究使用30天的中观宇宙实验阐明了浮游动物群落对鱼类捕食，杀虫剂毒死rif（CLP）以及这两种因素的组合的反应。在CLP毒性之前，浮游动物的组装受到鱼类存在的影响。鱼的捕食降低了微甲壳类的密度，从而导致了一个以微浮游动物为主的群落（即：轮虫和足无节幼体）。在有鱼和无鱼的处理中，CLP降低了物种的丰富度，从而导致Lepadella属中的轮枝轮虫数量增加和Trichocerca。当两种应激因素（鱼类捕食和杀虫剂毒性）组合在一起时，浮游动物：浮游植物（<20μm）的比例大大降低。尽管CLP在水相中消散相对较快，并在沉积物和鱼类组织中积累，但浮游动物的丰富度无法恢复。对此的可能解释可能是CLP对沉积物中静止阶段孵化的抑制作用。因此，鱼类捕食和CLP的共同作用可能影响浮游动物的丰富度，导致轮虫占主导地位的组合似乎对这两个因素均具有抵抗力，而控制浮游植物生长的能力有限。因此，在评估水生生态系统中的群落动态时，应同时考虑自然和人为压力源的影响。