Cold-season macrophyte-driven microbial modulation reduces nutrient release in eutrophic lake sediments

Submerged macrophyte restoration can effectively regulate internal nutrient cycling in eutrophic lake sediments, yet how cold-season macrophytes influence sediment microbial processes remain poorly understood. In this study, we conducted a field enclosure experiment combined with metagenomic sequencing using Potamogeton crispus, a cold-season submerged macrophyte, to investigate its effects on nitrogen (N) and phosphorus (P) dynamics across the sediment-water interface. The restoration of P. crispus led to marked decreases in the concentrations and sediment-to-water fluxes of bioavailable nitrogen (NH₄⁺, NO₃^-) and phosphorus (SRP, DGT-P). These reductions were accompanied by substantial shifts in microbial community structure and functional potential. Genes involved in nitrogen fixation and organic N metabolism were suppressed, while those related to nitrate reduction, nitrification, and nitrogen stress responses were enriched. Similarly, genes associated with phosphorus cycling exhibited increased diversity and abundance under restoration. Key microbial genes (e.g., gst, pqqB, ttdB) were strongly correlated with nutrient levels, indicating a potential role in nutrient stabilization. This study highlights the unique ecological function of cold-season macrophytes in regulating sediment biogeochemical processes and provides mechanistic insights into plant-microbe-nutrient interactions relevant to seasonally optimized lake management.