Trophic interaction in tropical regions is influenced by factors such as the size of organisms and the presence of intermediate predators. Macrophytes can act directly on predator–prey dynamics through the habitat structure provided by plants. We conducted an in situ mesocosm experiment (100 L) in a Brazilian reservoir to evaluate the top-down and bottom-up control promoted by the fish Astyanax lacustris, and to evaluate the effects of floating and submerged macrophytes’ morphology on trophic interaction. The experiment lasted ten days and consisted of four treatments in triplicate (n = 12): a control (C) without fish, with only the natural plankton community, and treatments with addition of fish (+ F), fish + floating macrophyte (+ FFM) and fish + submerged macrophyte (+ FSM). In treatments with macrophytes, artificial plants were added to serve as shelter for zooplankton and Chaoborus. Our results showed that fish reduced small cladoceran and Chaoborus biomass by top-down control and increased edible phytoplankton biomass by increasing nutrient concentrations by bottom-up control. Chaoborus increased the food chain length to four levels, with negative effects on the biomass of small cladocerans. Submerged macrophytes were more efficient in providing refuge for copepods and Chaoborus. In general, planktivorous fish had a direct effect on zooplankton and an indirect effect on phytoplankton, and the invertebrate Chaoborus interfered with the functioning of trophic networks. Our results show that, in experimental conditions, macrophytes can play a fundamental role in tropical reservoirs by reducing the strength of top-down control in the trophic cascade.

热带地区的营养相互作用受生物体大小和中间捕食者存在等因素的影响。大型植物可以通过植物提供的栖息地结构直接作用于捕食者 - 猎物动态。我们在巴西水库中进行了原位中宇宙实验 (100 L)，以评估鱼Astyanax lacustris促进的自上而下和自下而上的控制，并评估漂浮和沉水大型植物形态对营养相互作用的影响。实验持续十天，由四个处理组成，一式三份（n = 12)：没有鱼的对照 (C)，只有天然浮游生物群落，以及添加鱼 (+ F)、鱼 + 漂浮植物 (+ FFM) 和鱼 + 沉水植物 (+ FSM) 的处理。在用大型植物处理时，添加了人造植物作为浮游动物和Chaoborus的庇护所。我们的研究结果表明，鱼类通过自上而下的控制减少了小型枝角类动物和Chaoborus的生物量，并通过自下而上的控制增加营养浓度来增加可食用浮游植物的生物量。Chaoborus将食物链长度增加到四个水平，对小型枝角类动物的生物量产生负面影响。淹没的大型植物更有效地为桡足类和Chaoborus提供避难所. 一般来说，食浮游鱼类对浮游动物有直接影响，对浮游植物有间接影响，无脊椎动物Chaoborus干扰营养网络的功能。我们的研究结果表明，在实验条件下，大型植物可以通过降低营养级联中自上而下控制的强度在热带水库中发挥基础作用。