Basin governance coincides with lower MGE loads yet rewired ARG mobility: a hazard‑oriented, platform‑centric...

Antibiotic resistance genes (ARGs) serve as critical indicators for evaluating the ecological success of river restoration policies. We investigated the restructuring of the riverine resistome in the Yangtze River following the implementation of the "Ten-Year Fishing Ban" and the Yangtze River Protection Law. Using basin-wide surveys in the Jiangsu reach (2021 vs. 2023), we integrated shotgun metagenomics and RT-qPCR functional validation with a noise-filtering sampling design to assess how the removal of anthropogenic pressures reshaped resistance dissemination. Results show that policy-driven ecological recovery significantly altered microbial assembly mechanisms. While total ARG abundance declined, microbial communities shifted toward a more dispersal-dominated regime, with neutral model fits increasing from 0.817 to 0.913. Crucially, RT-qPCR analysis confirmed that the transcriptional activity of key resistance elements remained significantly elevated relative to a pristine baseline, suggesting persistent functional risks despite lower overall abundance. As localized selective pressures relaxed, the resistome transitioned toward integrated genetic platforms, evidenced by a significant rise in the mosaic index (MGI) from 12.81% to 22.50% (p < 0.05). Structural equation modeling (R2 = 0.766) identified a dominant sequential pathway from environmental co-selectors to mobile genetic elements and subsequently to ARGs, with intensified roles for integrons and insertion sequences (intI1, IS26). These findings demonstrate that policy success requires evaluation through both abundance-based and structural indicators. We propose a platform-centric surveillance framework incorporating the mosaic index as an early-warning tool for environmental agencies.