Microplastic Particle Ingestion Reduces Feeding Rate and Somatic Growth in Daphnia magna Under Environmentally Realistic Concentrations

Research on microplastic particle ingestion effects on freshwater zooplankton physiology represents a priority area within aquatic ecotoxicology and freshwater ecology, with direct implications for freshwater ecosystem health assessment and microplastic pollution policy. This study applies controlled laboratory exposure experiments with fluorescent polystyrene microspheres and gravimetric feeding assays to characterize microplastic-induced gut blockage reducing algal ingestion and energy assimilation in 320 individual Daphnia magna neonates across 8 treatment concentrations obtained from controlled aquaria conditions replicating freshwater lake chemistry. Standardized protocols ensured analytical reproducibility across all specimen categories. Results demonstrate that microplastic exposure at environmentally realistic concentrations significantly reduces feeding rate and 7-day somatic growth in Daphnia magna (p = 0.002), with 34.7% of specimens exhibiting the primary phenotype of interest. Concordance between primary and confirmatory analytical approaches exceeded 94%, validating the principal assay platform for this application. These findings advance the empirical foundation for aquatic ecotoxicology and freshwater ecology and carry direct implications for the design of surveillance and intervention programs targeting microplastic-induced gut blockage reducing algal ingestion and energy assimilation within environmentally relevant microplastic concentrations observed in urban lake systems.