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

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 (δ¹⁸O_P) 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 (F_SRP = 0.542SOU^0.410, 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. δ¹⁸O_P 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.