微塑料对大型溞摄食和抗氧化防御系统的影响

微塑料（Microplastics，MPs）作为一种新兴环境污染物，其环境效应已引起了广泛关注.为揭示不同粒径微塑料对淡水生物摄食和抗氧化防御系统的影响规律，以100 nm、5 μm、50 μm聚苯乙烯（Polystyrene，PS）微塑料为研究对象，以大型溞（Daphnia magna）为受试生物，研究微塑料在大型溞体内的积累量、停留量，以及对大型溞滤水率、摄食率以及抗氧化防御系统的影响.结果表明:3种粒径的微塑料均可被大型溞摄入，100 nm和5 μm的微塑料在大型溞体内的积累量和停留量均高于50 μm的微塑料，50 μm的微塑料主要黏附在胸肢处，而100 nm和5 μm的微塑料能在大型溞肠道中积累.暴露于3种粒径的微塑料后，大型溞的滤水率和摄食率较对照组分别降低了50.7%±9.5%和39.2%±10.7%.3种粒径的微塑料均能促进大型溞体内超氧化物歧化酶、过氧化氢酶活性的升高，并诱导丙二醛含量升高，导致大型溞氧化损伤.研究显示，微塑料损伤大型溞的食物过滤器，堵塞消化道，降低其滤水率、摄食率，造成大型溞氧化损伤，微塑料暴露对大型溞的摄食和抗氧化防御系统造成了不利影响. 

Effects of Microplastics on Feeding Behavior and Antioxidant System of Daphnia magna

Microplastics (MPs), an emerging environmental pollutant, have drawn increasing public concerns for its detrimental environmental effects. To evaluate the effects of MPs with different sizes on feeding behavior and antioxidant system of freshwater organisms, three different sizes of polystyrene microplastics (i.e. 100 nm, 5 μm, 50 μm) were selected to investigate the accumulation and residence of MPs in Daphnia magna, and the influence of MPs on the filtration rate, feeding rate, and antioxidant system of Daphnia magna. The results showed that all MPs could be ingested by Daphnia magna, and the accumulation and residence of MPs with a size of 100 nm and 5 μm in Daphnia magna were higher than 50 μm. Moreover, MPs with a size of 50 μm were mainly adhered to the thorax appendages, while MPs with a size of 100 nm and 5 μm could be accumulated in the intestines of Daphnia magna. After exposure to the three MPs, the filtration rate and feeding rate of Daphnia magna decreased by 50.7%±9.5% and 39.2%±10.7% compared with the control group, respectively. Furthermore, the activity of superoxide dismutase and catalase, and the content of malondialdehyde in Daphnia magna increased significantly, and the oxidative system of Daphnia magna was damaged. Overall, the exposure of MPs can cause the damage to the feeding filter of Daphnia magna, block the digestive tract, inhibit the filtration rate and feeding rate, and ultimately lead to the damage of oxidative system Daphnia magna. Therefore, the exposure of MPs can lead to adverse effects on feeding behavior of Daphnia magna.