Knowledge on the impacts of microplastics (MPs) pollution on freshwater environments and biota remains limited. Meanwhile, freshwater ecosystems have been threatened by elevated temperatures caused by climate change. To date, no information exists on how MPs—especially under elevated temperature conditions—affect predatory performance, digestive processes and metabolic pathways in freshwater organisms. Here, we examined MPs, elevated temperature and their combined effects on juveniles (0+ group) of an Amazonian cichlid, the discus fish (Symphysodon aequifasciatus). For 30 days, fish were exposed to ambient or elevated temperatures (i.e., 28 or 31 °C) in the absence or presence of MPs (i.e., 0 or 200 μg/L). The following metrics were quantified: MPs accumulation; predatory performance; and biomarkers involved in neurotransmission, digestion and energy production. The results showed that survival rate and body length were not affected by MPs, elevated temperatures or their combination. Elevated temperatures resulted in an increase in MP concentrations in fish bodies. Exposure to MPs decreased the post-exposure predatory performance (PEPP) at ambient temperatures but not at elevated temperatures. Elevated temperatures, however, had no effect on the PEPP but antagonistically interacted with MPs, leading to similar predatory performances under present and future conditions. Acetylcholinesterase (AChE) activity was only affected by MPs and decreased in the presence of MPs, indicating adverse effects in nervous and neuromuscular function and, thus, potentially in predatory performance. Trypsin activity was only influenced by MPs and decreased during exposure to MPs. Elevated temperatures or MPs alone increased the amylase activity but interacted antagonistically. Lipase activity was not influenced by either of the two stressors. In contrast, alkaline phosphatase (ALP) activity was affected by MPs or elevated temperatures alone and decreased with both stressors. Such results indicate deficits in the digestive capabilities of early-stage S. aequifasciatus under elevated temperature conditions and especially during exposure to MPs. Electron transport system (ETS) activity was not influenced by either of the two stressors. Both elevated temperatures and MPs alone increased LDH activity; however, the interaction between the two stressors cancelled activity but was still higher than activity in present conditions. Citrate synthase (CS) activity decreased with elevated temperature but increased during exposure to MPs. Cytochrome c oxidase (COX) activity was only influenced by MPs and increased in the presence of MPs. Thus, S. aequifasciatus juveniles exposed to elevated temperatures and MPs not only relied on anaerobic glycolysis for energy production but also depended on aerobic metabolism in the presence of MPs. Overall, these findings suggested that MPs showed a greater impact than elevated temperatures on the predatory performance, digestion and energy production of S. aequifasciatus. Nevertheless, juvenile survival and growth were minimally impacted, and thus, S. aequifasciatus could cope with near-future temperature increases and MP exposure.

关于微塑料（MPs）污染对淡水环境和生物区系影响的知识仍然有限。同时，气候变化导致的高温威胁着淡水生态系统。迄今为止，尚无关于MPs（尤其是在高温条件下）如何影响淡水生物中捕食性能，消化过程和代谢途径的信息。在这里，我们检查了MP，温度升高及其对亚马逊慈鲷，铁饼鱼（Symphysodon aequifasciatus）的幼体（0+组）的综合影响）。在不存在或存在MP（例如0或200μg/ L）的情况下，将鱼暴露于环境或高温（即28或31°C）下30天。量化了以下指标：MP积累；掠夺性表演 以及涉及神经传递，消化和能量产生的生物标志物。结果表明，MP，升高的温度或它们的组合不影响存活率和体长。温度升高导致鱼体内MP含量增加。在环境温度下，MP的暴露会降低暴露后的掠食性性能（PEPP），但在升高的温度下则不会。但是，升高的温度对PEPP没有影响，但与MP产生拮抗作用，导致当前和未来条件下类似的掠食性表现。乙酰胆碱酯酶（AChE）的活性仅受MP的影响，而在MP的存在下降低，表明对神经和神经肌肉功能有不利影响，因此可能对掠食性行为有不利影响。胰蛋白酶的活性仅受MP的影响，而在MP暴露期间则降低。升高的温度或单独的MP会增加淀粉酶的活性，但会产生拮抗作用。脂肪酶的活性不受两个应激因素之一的影响。相比之下，碱性磷酸酶（ALP）的活性仅受MPs或升高的温度的影响，而在两种应激源下均降低。这样的结果表明早期消化能力的不足 胰蛋白酶的活性仅受MP的影响，而在MP暴露期间则降低。升高的温度或单独的MP会增加淀粉酶的活性，但会产生拮抗作用。脂肪酶的活性不受两个应激因素之一的影响。相比之下，碱性磷酸酶（ALP）的活性仅受MPs或升高的温度的影响，而在两种应激源下均降低。这样的结果表明早期消化能力的不足 胰蛋白酶的活性仅受MP的影响，而在MP暴露期间则降低。升高的温度或单独的MP会增加淀粉酶的活性，但会产生拮抗作用。脂肪酶的活性不受两个应激因素之一的影响。相比之下，碱性磷酸酶（ALP）的活性仅受MPs或升高的温度的影响，而在两种应激源下均降低。这样的结果表明早期消化能力的不足S.神仙升高的温度条件下，特别是暴露于国会议员期间。电子传输系统（ETS）的活动不受两个压力源中的任何一个的影响。升高的温度和MP单独增加LDH活性；然而，两个应激源之间的相互作用抵消了活性，但仍高于当前条件下的活性。柠檬酸合酶（CS）活性随温度升高而降低，但在暴露于MPs时升高。细胞色素C氧化酶（COX）的活性仅受MP的影响，并在MP的存在下增加。因此，水母链球菌暴露于高温和MPs的幼鱼不仅依靠厌氧糖酵解产生能量，而且还依赖于MPs存在时的有氧代谢。总体而言，这些发现表明国会议员们对高温马链球菌的掠食性能，消化和能量产生的影响比升高的温度更大。尽管如此，对幼虫的存活和生长的影响却很小，因此，马链球菌可以应对近来的温度升高和MP暴露。