Reed root-biofilm systems are associated with cadmium depletion in wetland soils, along with extracellular polymeric substances compositional shifts and distinct bacterial enrichment

Cadmium (Cd) contamination in wetland soils poses a severe threat to ecosystem health, yet traditional remediation strategies often lack efficient, self-sustaining mechanisms for long-term depletion. This study investigates the roles of reed root-biofilm (RRB) systems in Cd depletion and shaping microbial community structure. Through a 240-day factorial microcosm experiment involving five treatment groups (bulk soil, sterilized soil, reed root-biofilm alone, and their combinations) across a Cd concentration gradient (0-10mg/kg), and integrating ICP-OES analysis, extracellular polymeric substances (EPS) 3D fluorescence spectroscopy, and high-throughput amplicon sequencing, the results show that RRB amendment was associated with Cd depletion zones in bulk soil (reducing total Cd concentrations from 10 to 4.25mg/kg), compared to the unamended controls. This process was associated with the secretion of protein-like and humic-like EPS, with protein-like fluorescence intensity reaching 569.9 in the root-biofilm treatment group. Notably, RRB amendment was associated with a consortium enrich in Methylophaga, Rheinheimera, Azoarcus, and Desulfuromonas, while maintaining high Shannon diversity (6.48) under metal stress. Unlike sterile controls that relied solely on abiotic adsorption, RRB amendment was associated with a coordinated pattern of EPS compositional changes and microbial community shifts. These findings suggest that RRB-associated Cd depletion coincided with EPS compositional changes and microbial community shifts. This study provides a basis for developing root-biofilm-based strategies to improve both Cd depletion efficiency and process sustainability in contaminated wetland remediation.