Wen Bin, Zhang Nan, Jin Shi-Rong, Chen Zai-Zhong, Gao Jian-Zhong, Liu Ying, Liu Han-Peng, Xu Zhe
Key Laboratory of Freshwater Aquatic Genetic Resources, Ministry of Agriculture, Shanghai Ocean University, Shanghai 201306, China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China; Shanghai Collaborative Innovation for Aquatic Animal Genetics and Breeding, Shanghai Ocean University, Shanghai 201306, China.
Key Laboratory of Freshwater Aquatic Genetic Resources, Ministry of Agriculture, Shanghai Ocean University, Shanghai 201306, China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China; Shanghai Collaborative Innovation for Aquatic Animal Genetics and Breeding, Shanghai Ocean University, Shanghai 201306, China.
Aquat Toxicol. 2018 Feb;195:67-76. doi: 10.1016/j.aquatox.2017.12.010. Epub 2017 Dec 26.
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群影响的认识仍然有限。与此同时，淡水生态系统受到气候变化导致的温度升高的威胁。迄今为止，尚无关于微塑料（尤其是在高温条件下）如何影响淡水生物的捕食性能、消化过程和代谢途径的信息。在此，我们研究了微塑料、高温及其联合效应对亚马逊丽鱼科鱼类七彩神仙鱼（Symphysodon aequifasciatus）幼鱼（0 +组）的影响。在30天的时间里，将鱼置于不存在或存在微塑料（即0或200μg/L）的环境温度或高温（即28或31°C）条件下。对以下指标进行了量化：微塑料积累；捕食性能；以及参与神经传递、消化和能量产生的生物标志物。结果表明，存活率和体长不受微塑料、高温或它们的组合的影响。高温导致鱼体内微塑料浓度增加。在环境温度下，接触微塑料会降低暴露后捕食性能（PEPP），但在高温下则不会。然而，高温对PEPP没有影响，但与微塑料产生拮抗作用，导致当前和未来条件下的捕食性能相似。乙酰胆碱酯酶（AChE）活性仅受微塑料影响，在存在微塑料的情况下会降低，表明对神经和神经肌肉功能有不利影响，从而可能影响捕食性能。胰蛋白酶活性仅受微塑料影响，在接触微塑料期间会降低。单独的高温或微塑料会增加淀粉酶活性，但两者产生拮抗作用。脂肪酶活性不受这两种应激源中的任何一种影响。相反，碱性磷酸酶（ALP）活性单独受微塑料或高温影响，在两种应激源共同作用下会降低。这些结果表明，在高温条件下，尤其是在接触微塑料期间，早期七彩神仙鱼的消化能力存在缺陷。电子传递系统（ETS）活性不受这两种应激源中的任何一种影响。单独的高温和微塑料都会增加乳酸脱氢酶（LDH）活性；然而，两种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，但在接触微塑料期间会增加。细胞色素c氧化酶（COX）活性仅受微塑料影响，在存在微塑料的情况下会增加。因此，暴露于高温和微塑料的七彩神仙鱼幼鱼不仅依靠无氧糖酵解产生能量，而且在存在微塑料的情况下还依赖有氧代谢。总体而言，这些发现表明，微塑料对七彩神仙鱼的捕食性能、消化和能量产生的影响比高温更大。然而，幼鱼的存活和生长受到的影响最小，因此，七彩神仙鱼能够应对近期的温度升高和微塑料暴露。
