Spatiotemporal distribution and host association of antibiotic resistance genes in sediment of Qiantang river basin.

= 0.856, Pearson's r = 0.925), highlighting the role of transposons and integrons in facilitating ARG propagation within sedimentary microbial communities. Sediment bacterial hosts, particularly Proteobacteria (e.g., Phenylobacterium, Thioalkalivibrio, Cupriavidus) and Chloroflexi (e.g., Anaerolinea), were strongly associated with Risk Rank I genes such as aac(3)-I and aac(3)-IV, encoding aminoglycoside acetyltransferases (AACs). The co-occurrence patterns of ARGs with hosts and human pathogens in sediments suggest that ARG subtypes such as golS, ompR, and ksgA are most closely related to their hosts. Notably, antibiotic concentrations in water and sediments correlated positively with both MGEs and ARG diversity, emphasizing the synergistic effects of anthropogenic pollutants. This study provides new insights into the occurrence and transmission of ARGs in estuarine environments and offer an omics-based assessment strategy for the public health risks associated with AMR.