Small-sized microplastics drive structural shifts in aquatic communities: Evidence from the Wei River Basin

The growing ecological concerns regarding microplastic (MP) pollution in freshwater ecosystems have highlighted the need to understand its associations with aquatic community structure, particularly in the Wei River Basin where such relationships remain poorly characterized. This study systematically investigates the distribution patterns and ecological correlations of MPs in this critical watershed system, revealing contamination levels of 1500-5167 items/m³ in water and 480-2670 items/kg in sediments. Compositional analysis identified a predominance of small (<1 mm), white/transparent fibrous particles, reflecting distinct source characteristics. Statistical analysis indicated that MP size emerged as the strongest statistical predictor of community variation in our dataset, with the < 50 μm and 50-100 μm fractions showing the most pronounced associations, while morphological and color characteristics exhibited minimal statistical influence. The partial least squares path model (PLS-PM) illustrated potential transfer pathways between aquatic compartments, with MPs in water showing stronger correlations with zooplankton communities, whereas MPs in sediment were more closely associated with zoobenthos communities. These findings provide insight into the size-dependent correlations and compartment-specific statistical relationships of MPs in riverine ecosystems.