In this study, effects of polystyrene microplastics (MPS) on Euglena gracilis were investigated via examination on its photosynthesis and motility, two typical properties of the protozoan. No adverse effects were observed after 4-d exposure except for decrease in motility at two high MPS concentrations (5 and 25 mg/L). After 8-d duration, MPS at 1 mg/L had no obvious effects on E. gracilis, but two higher concentrations (5 and 25 mg/L) of MPS inhibited protozoan growth, motility, and photosynthesis. The reduced protozoan photosynthetic activity was reflected by changes in F_v/F_m (the maximum photochemical yield of PSII), ΔF_IP (difference between F_P and F_I) and PI_ABS (the performance index), indicative of reduced quantum yield of electron transport and enhanced energy dissipation. A dose-dependent effect of MPS on E. gracilis was found in protozoan growth, photosynthesis and motility, especially photosynthetic indices. MPS of small size (75 nm) seemed more toxic to the protozoa than large size (1000 nm). Internalization of MPS in the cells and chloroplasts was observed clearly for the first time, likely responsible for their toxicity. Analysis on photosynthetic process and motility of E. gracilis could provide more comprehensive understanding of MPS toxicity in the aquatic environment, and may potentially serve as a biomonitoring tool.

在这项研究中，通过检查其光合作用和运动性（原生动物的两个典型特性），研究了聚苯乙烯微塑料（MPS）对Euglena gracilis的影响。4d暴露后未观察到不良影响，除了在两种高MPS浓度（5和25 mg / L）下运动性降低。经过8天的时间后，MPS浓度为1 mg / L时对纤毛大肠杆菌没有明显影响，但是两种较高浓度的MPS（5和25 mg / L）抑制了原生动物的生长，运动性和光合作用。减小的原生动物光合活性通过改变反射˚F _v / ˚F_米（PSII的最大光化学产率），Δ ˚F _IP（间差˚F _P和F _I）和PI _ABS（性能指标），表明电子传输的量子产率降低和能量耗散增强。MPS上的剂量依赖性效果小眼虫在原生动物生长，光合作用和运动性，特别是光合索引找到。小尺寸（75 nm）的MPS似乎比大尺寸（1000 nm）对原生动物更具毒性。首次清楚地观察到MPS在细胞和叶绿体中的内在化，可能是其毒性的原因。分析光合作用过程和活力眼虫可以在水生环境中提供MPS毒性更全面的了解，且有可能作为生物监测工具。