Effects of microsized and nanosized polystyrene on detrital processing and nutrient dynamics in streams

POLLUTION FROM MICRO: and nanoplastics has become a significant concern for the health and functioning of freshwater ecosystems. However, a comprehensive understanding of how these contaminants disrupt key ecological processes and alter species interactions remains largely unknown. The present study evaluated the size- and concentration-dependent effects of polystyrene particles (50 nm and 1 μm; 1 and 10 μg L^-1) on a detrital food chain. Specifically, we focused on how microbial decomposers responded in terms of metabolic activity and extracellular enzyme activity, as well as the river snail Cipangopaludina cathayensis in relation to its growth rate, consumption activity, and nutrient acquisition. After 25 days of exposure, 10 μg L^-1 nanosized polystyrene particles significantly depressed the microbial growth and promoted the activity of N-acetylglucosaminidase, polyphenol oxidase, and β-glucosidase, which enhanced leaf lipid accumulation and then decreased the decomposition rate of C. cathayensis. Microsized polystyrene particles caused a temporary decrease in microbial metabolic activity, reduced the leaf nitrogen content, leading to a significant decline in nitrogen acquisition ability and consumption activity of the river snail. These results implied that nanosized and microsized polystyrene particles exhibited different impacts on detrital processing and nutrient dynamics by influencing specific functional traits within the detrital food chain. In conclusion, the study emphasized the importance of assessing the multi-level potential impact of plastic pollution on the food chain in streams, which is essential for understanding the broader ecological consequences, including shifts in community structure and ecosystem functioning in freshwater ecosystems.