Dredging-Induced Sediment Plume Dispersion and Mangrove Seedling Growth Response in the Estuary Reach of the Pinglu Canal

Channel dredging at the estuary section of the Pinglu Canal increases suspended sediment concentration (SSC) and induces sediment plume dispersion,posing potential risks to mangrove ecosystems.This study combined a two-dimensional hydrodynamic-sediment transport model with siltation stress experiments on Kandelia obovata seedlings to investigate the transport characteristics of dredging-induced sediment plumes and SSC-dependent growth responses of seedlings.Results showed that,under dry-season spring tide conditions,the peak SSC of dredging plumes decreased exponentially with distance from the source,exhibiting long-distance transport along the main flow direction and rapid lateral dilution.Kandelia obovata seedlings maintained normal growth under initial SSC levels of 0~50mg/L,while significant growth inhibition occurred at approximately 100mg/L.Growth deterioration occurred at 400mg/L and above,and mortality occurred when initial SSC reached 600mg/L or higher.The peak SSC in mangrove areas increased approximately linearly with dredging source strength.When the source strength was approximately 2.3kg/s,the peak SSC at typical mangrove sites approached 100mg/L,while the peak SSC exceeded 200mg/L in some areas at a source strength of 6.9kg/s.These findings provide a scientific basis for dredging intensity control and mangrove protection in the Pinglu Canal estuary.