不同粒径聚乙烯微粒对大型溞的生物毒性效应

微塑料污染已经受到了国内外研究者的广泛关注，但研究热点多集中于海洋微塑料及其生物学效应，对淡水生物潜在影响的研究还很有限。本文选择淡水模式动物大型溞（Daphnia magna）作为受试生物，以2 μm、20 μm和50 μm聚乙烯微粒（polyethylene，PE）作为研究对象，探讨不同尺度微塑料对大型溞的急性活动抑制效应。结果表明，3种粒径的微塑料均可被大型溞摄入，并在肠道中积累，造成大型溞的活动抑制，并可能影响其脂类代谢；水中高浓度的PE微粒可粘附在大型溞体表，限制其活动，影响其摄食。在5~80 mg/L浓度范围内，2 μm PE微粒对大型溞的抑制率呈现线性增长趋势（96 h的EC₅₀为50.86 mg/L）；而20 μm和50 μm的PE微粒的抑制率随暴露浓度的增加呈现倒"U"形曲线。暴露48 h后，3种PE微粒的LOEC值分别为60、20和5 mg/L，即随粒径增大，毒性效应增加。粒径大小是影响大型溞摄入和积累微塑料的重要因素之一。本文结果为深入理解微塑料对淡水浮游动物的毒性效应提供了基础数据和理论依据。

Toxic effects of different particle size polyethylene microbeads on Daphnia magna

Microplastics (MPs) contamination represents a dramatic environmental problem threatening both freshwater and marine organisms.Although several studies have highlighted the presence of MPs in aquatic environments, the information regarding their toxicity towards freshwater organisms is still scant.In this paper, Daphnia magna, a freshwater cladoceran, was selected as the test organism in this study.3 sizes of polyethylene (PE) particles, including 2 μm, 20 μm and 50 μm, were used to investigate their acute toxic effects according to OECD guideline for water flea acute immobilisation test.The results showed that all three sizes of PE particles could be ingested by water flea and accumulated in their guts, which caused the immobilization and may affect their lipid metabolism.PE particles in water could adhere to the body of animals, affecting their moving and feeding.In the concentration range of 5~80 mg/L, ingestion of 2 μm PE particles led to immobilisation increasing with dose and time with an EC₅₀ of 50.86 mg/L after 96 h exposure; for 20 μm and 50 μm PE particles, however, the immobilization appeared an inverted U-shaped curve with the dose increasing.After 48 h exposure, the LOEC values of the 3 sizes of PE particles were 60, 20 and 5 mg/L, respectively.It is indicated that particle size is one of the important factors affecting the ingestion and accumulation of MPs in water flea.These results underline that MPs can induce adverse effects in freshwater zooplankton and potentially impact the function of the ecosystem.