Diversity, structure, and network relationships of microbial communities in different areas of the upper reaches of the Jinghe River, China

The Jinghe River, as one of the rivers flowing into the Yellow River, China, exhibits ecosystem vulnerability to agricultural activities and urbanization. However, the impact of agricultural activities and urbanization process on the physical-chemical properties and microbial community structure in its upper reaches has not been fully documented. This study selected three distinct sections along the upper Jinghe River: the Liupan Mountains Nature Reserve (upstream), agricultural area (midstream), and urbanized area (downstream). Through combined analysis of river physical-chemical parameters with high-throughput sequencing of bacterial and fungal communities, the results indicated significant increases in river water electrical conductivity (19.60%) and ammonium nitrogen content (170.74%) from the protected area to the urban section. Conversely, significant decreases were observed in total carbon (31.74%), total organic carbon (32.60%), dissolved organic carbon (27.91%), and nitrate nitrogen concentrations (53.44%). The abundance-based coverage estimation (ACE) index of bacteria was significantly higher in urban areas than in the protected area. The ACE index of fungi and the relative abundance of Proteomycota and Ascomycota were significantly higher in the protected area than in the urban area. Co-occurrence network analysis revealed higher complexity in the microbial network within the protected area and greater modularity in agricultural area, whereas the network structure in the urban area was simplified, indicating weakened network stability due to human disturbance. Furthermore, the abundance and distribution of Acidobacteriota were significantly and negatively correlated with river carbon components ( P <0.01), highlighting its crucial potential role in carbon cycling. This research aims to elucidate changes in water physical-chemical characteristics, microbial community structure, diversity, and interaction networks under human influence, providing a scientific basis for water resource management and ecological conservation in arid areas.