Impact of land use on antibiotic resistance genes and bacterial communities in rivers

River ecosystems support essential ecosystem functions and services, including supplying water for domestic, agricultural, and industrial activities, provisioning of hydropower and fisheries, supporting navigation and recreational activities, and regulating water quality. In recent decades, the presence and spread of antibiotic resistance genes (ARGs) have emerged as a key threat to ecosystem health and human well-being. Rivers that are surrounded by human-modified landscapes serve as primary repositories and sources of ARGs. However, our understanding of the relationship between the diversity of ARGs and land use remain limited. We collected 30 sediment samples from five rivers in Ningbo, China, and then classified the sampling sites into two groups (i.e., group A with low levels of human impacts and group B with intense human impact) based on land use in their upstream areas. In total, we found 31 types of ARGs and 148 phyla of bacteria in the samples. ARGs abundance had a positive relationship with the levels of anthropogenic activities, and exhibited significant difference between the two groups. Co-occurrence networks showed that the interrelationship between bacteria and ARGs was more complex in group B than in group A. Moreover, Structural Equation Modeling (SEM) revealed that anthropogenic activity not only posed direct effect on ARGs but also indirectly affected ARGs through bacteria. Our results underscore the profound impacts of land-use changes on the diversity of ARGs, bacteria communities, and their relationships, which highlight the need for integrating ARGs in river assessments in regions with human-dominated land use.