Redeposited particles mitigate dredging effect on internal phosphorus loading by supplying phosphorus and fueling sediment phosphorus cycling.

Sediment dredging is widely applied to mitigate sediment P loading in hypereutrophic systems, yet its long-term effectiveness under dynamic particle deposition remains poorly constrained. In this study, a one-year field incubation in Lake Taihu combined high-resolution porewater solute profiling, benthic chemical flux measurements, microbial network analysis, sediment characterization, and phosphate oxygen isotope (δ18OP) tracing to investigate sediment P biogeochemistry following simulated-dredging with/without settling particle inputs. Dredging suppressed porewater SRP and Fe2+ accumulation, and benthic SRP flux, thereby limiting sediment P remobilization in the absence of settling particles. However, under continuous particle deposition, sediment P cycling was rapidly re-established, particularly during warm seasons. Notably, benthic SRP efflux followed a power-law relationship with sediment oxygen uptake (FSRP = 0.542SOU0.410, r2 = 0.93), indicating additional P contributions from redox-mediated feedbacks, such as Fe-P remobilization, beyond organic matter remineralization alone. Microbial and phosphate solubilizing bacteria (PSB) networks were simplified yet more stable after dredging, but particle inputs weakened this effect, reinforcing coupled biogeochemical cycling. δ18OP fingerprints further revealed that post-dredging sediment recovery was primarily fueled by redeposition of re/suspended local particles rather than nonlocal inputs. Dredging triggers an interruption of intralake P recycling but should be applied alongside complementary geoengineering to optimize eutrophication management.