[Response of Water-Vallisneria natans-Sediment System to Polyethylene Microplastics]

The microplastics in aquatic ecosystems pose a serious threat to ecological security and environmental health, which have received widespread attention. To reveal the response of a water-Vallisneria natans-sediment system to microplastics exposure, the V. natans was exposed to polyethylene microplastics （PE-MPs） with different mass fractions （1%-5%, sediment wet mass fraction）, and the effects of PE-MPs on the physiochemical indicators of water quality, morphological characteristics of submerged plants, physiological characters, antioxidant system, and microbial community structure in sediments were studied respectively. The results showed that the physiochemical properties of the water body were not significantly changed in the PE-MPs treatment group, whereas the plant height, oxidative stress index, and antioxidant system were significantly inhibited. For the plant height, the 1% PE-MPs treatment group height was only 47.44% of that in the control group. Chlorophyll a content was 81.04% of that in the control group, and the activities of catalase （CAT）, malondialdehyde （MDA）, and peroxidase （POD） increased by 233.70%, 117.82%, and 61.62%, respectively. Different mass fractions of PE-MPs had a certain impact on microbial community structure in sediments. The above results are helpful to improve the evaluation system of PE-MPs ecological risk in the water-submerged plant-sediment system.