SMFC-driven disruption of iron-sulfur redox coupling as a bioelectrochemical barrier against endogenous phosphorus release in eutrophic lake Taihu, China

Legacy sedimentary phosphorus undergoes microbially mediated reactivation, perpetuating harmful algal blooms. Sediment microbial fuel cells (SMFCs) suppress phosphorus liberation through targeted manipulation of sulfur-driven iron reduction, whereas their integrated impacts on biogeochemical cycling and microbiome dynamics in complex eutrophic environments require systematic elucidation. In this study, a two-chamber SMFC system was constructed to investigate the electrochemical regulation of phosphorus (P), iron (Fe), and sulfur (S) cycling dynamics. Phosphorus transfer-transformation mechanisms were elucidated through cross-interface physicochemical characterization of anode sediment-overlying water interfaces, continuous voltage monitoring, and metagenomic community profiling. The results showed that the closed-circuit SMFC significantly altered sediment pH compared to control, with gradual decreases at deeper depths. This pH change correlated with a 71 % reduction in overlying water total phosphorus. Concurrently, a 21.46 % SO₄^2- increase in deep pore water (−6 cm) confirmed enhanced sulfur oxidation, suppressing PO₄^3- release. Solid-phase analysis revealed a 7.09 % reduction in NaOH-P (metal-bound P) at mid-depth (−3 cm). An accompanying BD-P (Fe-bound P) increase confirmed slowed iron reduction, inhibiting phosphate release. The relative abundances of Pseudomonadota and Chlorobi, to which sulfur-oxidizing bacteria belong, were 23.06 % and 18.35 %, respectively, which were significantly higher than those of the control group, indicating that the SMFC has a significant enrichment effect on specific functional microbial communities. This study reveals that SMFCs alter sediment redox dynamics by accelerating sulfur oxidation while suppressing iron reduction, thereby inhibiting phosphorus release. These mechanistic advances deepen understanding of phosphorus biogeochemistry in disturbed sediments, offering scientific basis for future global eutrophication control strategies.