Towards sustainable management of riverine ecosystems: Variability of microplastic diversity and distribution patterns in ecosystem compartments

As emerging environmental chemicals, Microplastic (MP) pollution in global freshwater environment receives an increasing attention due to hazardous effect to human and environmental health. However, there is still minimal understanding on variability of MP diversity and distribution patterns in riverine ecosystem compartments. And field data are also lacking. All above hindered providing more science-based information for mechanisms of transport and interdisciplinary studies dealing with environmental chemistry and toxicology in global freshwater environment. Hence, our study focused on variability of MP diversity and distribution patterns in riverine ecosystem compartments. By undertaking MP community analyses, we found that distribution and variation in MP characteristics and communities among ecosystem compartments differed significantly. Moreover, structural characteristics of MP communities across compartments were distinct but not fully isolated, reflecting a balance between dispersion and niche differentiation (environmental filtering). Specifically, surface water and sediments mainly accumulated a greater abundance of smaller-sized, low-density, and fibrous MPs. Their distribution patterns were similar and mainly affected by population density, flow velocity, and precipitation. The distance-decay relationship of MP communities in surface water was stronger ( p < 0.001) than that in sediment and soil. The longitudinal connectivity of the river, input of pollution sources and tributaries also facilitated transport of MP particles. Meanwhile, the retention of MPs in sediment was significantly influenced by MP characteristics and sediment grain size; and higher diversity (1.82) and abundance of MPs (130.32 items/kg) deposited in sediment also suggested continuous accumulation. The transport of MPs in riparian soil revealed a preference via vertical direction and to adjacent sites. Considering limited transport capacity and significant correlations between topsoil and water/sediment, riparian soil may act as a potential long-term sink for river MPs. Although case-specific, results of this study are analyzed within a wider framework to enhance understanding of fate and transport dynamics of MP within global riverine ecosystems. • Higher diversity and abundance of microplastics (MPs) deposited in sediment than in water and soil. • MPs in riparian soil tended to be transported via vertical direction and to adjacent sites. • Distance-decay relationship of MP communities in surface water was stronger than that in sediment and soil. • Significant differences in MP communities among three ecosystem compartments were detected. • Not fully isolated structural characteristics of MP communities reflect a balance between dispersion and niche differentiation.