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The particle size of plastic is one of the most important factors influencing its ecotoxicity, but we are unclear about the effect of polystyrene (PS) particle size on microbial decomposers and consequent nutrient cycling in streams. Here, using microcosm experiments, we assessed how three PS sizes (50 nm, 1 μm, and 20 μm) influenced the process and consequences of leaf litter decomposition. Under acute exposure to 1 μm and 20 μm PS, fungal biomass significantly decreased, but microbial biomass significantly increased, indicating compensations may work between fungi and other microbial decomposers. After chronic exposure to 50 nm and 1 μm PS, the leaf decomposition rate decreased by 19.27 % and 15.22 %, respectively, due to the reduced microbial enzyme activity, fungal diversity, and dominance of Anguillospora. As a result, the regeneration of nutrients, especially phosphorus, was significantly depressed, which might influence the primary productivity of streams. Therefore, our results suggest that nanoscale PS has a greater impact on microbial activity, thus affecting their functioning in leaf litter decomposition and consequent nutrient cycling. The findings provide a data support for the risk assessment of plastic pollution in freshwater systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The pattern of acid rain is dependent on the ratio of SO 4 2- and NO 3 - , which change may affect the dissolution activity of dull heavy metals in the aquatic environment and further complicate the ongoing challenge of ecosystem stability and increase risks. In this study, we assessed the combined effects of acid rain (SO 4 2- : NO 3 - was 2:1, 1:1, and 1:2) and ZnO nanoparticles (30 ng L -1 ) on plant litter decomposition through a microcosm experiment. The highest dissolution of ZnO nanoparticles was achieved when the SO 4 2- : NO 3 - ratio was 1:2, and there were no significant differences among other treatments. The fungal biomass showed significant decreases under acute exposures but tended to be adaptive during chronic exposures. The co-exposure significantly stimulated the activities of leucine-aminopeptidase, glycine-aminopeptidase, polyphenol oxidase, and cellobiohydrolase. Besides, the fungal diversity and the relative abundance of some functional genera (e.g. Anguillospora) were enhanced when the SO 4 2- : NO 3 - ratio was 1:2 and 2:1. In conclusion, the decomposition rate of plant litter was increased by 123-204% by co-exposures. Collectively, the findings underline the importance of considering environmental context to assess nanoparticle toxicity., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Many studies have proved the impacts of nanoplastic pollution in freshwaters on aquatic organisms and ecosystems. To explore toxic mechanisms of nanoplastics on stream functioning, we conducted a microcosm experiment to investigate the effects of polystyrene nanoparticles (PS NPs, 1-100 μg L -1 ) on the process of leaf litter decomposition mediated by the microbial community. The chronic exposure to PS NPs at 1 and 100 μg L -1 caused significant decreases in leaf litter decomposition and nutrient (carbon and nitrogen) releases. During the ecological process, some extracellular enzymes (i.e., β-glucosidase, glycine-aminopeptidase, and phenol oxidase) rather than fungal biomass were suppressed. Besides, decreases in the relative abundance of Anguillospora and Setophaeosphaeria weakened their functions in leaf litter decomposition. Thus, the microcosm experiment showed that PS NPs inhibited stream leaf decomposition by modulating the microbial metabolic activity and fungal community structure. Overall, the results of this study provide evidence for the consequences of nanoplastic pollution on freshwater microbial community and stream ecosystem functioning, which is conducive to evaluate the potential risks of nanoplastics in aquatic environments., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Synthesis of zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs) and evaluation of their potential threats on ecosystem functioning has been reported in this work. A 45-day indoor experiment was conducted to explore the effects of ZIF-8 NPs at three different concentrations (10, 100, and 1000 μg L -1 ) on the aquatic fungal community associated with Populus nigra L. leaf litter decomposition. After chronic exposure, ZIF-8 NPs at 1000 μg L -1 significantly inhibited fungal biomass and extracellular enzyme activities as a result of inhibition on carbon and nitrogen loss of leaves. Besides, ZIF-8 NPs at 10 μg L -1 increased the percentage of Anguillospora in the fungal community and led Monographella cucumerina and Mycosphaerella tassiana to become the hub species, which eventually significantly promoted the decomposition of leaf litter. In conclusion, our study provides a reference for the possible ecotoxicity of ZIF-8 NPs on aquatic fungi, confirms the influence of ZIF-8 NPs on nutrient cycling in streams, and also emphasizes the importance of fungal community structure and hub species in the process of leaf litter decomposition., (Copyright © 2020 Elsevier B.V. All rights reserved.)