Submerged Plant Restoration Modulates Carbon-Water Interface Dynamics: Enhanced Carbon Sequestration Coupled with Eutrophication Control

This study investigates the dynamics of carbon flux at the water–air interface during the ecological restoration of eutrophic water bodies. A controlled simulation of the eutrophic aquatic environment was carried out. A series of experiments was established, centered on submerged aquatic plants as key agents for carbon sequestration and enhancement of carbon sink capacity, supplemented by biological manipulation techniques aimed at pollution reduction and algal control. Results show that restoration systems based on submerged plants significantly enhance carbon sequestration, whereas systems relying solely on filter-feeding fish tend to increase the carbon emission burden. The submerged plant-only treatment (HV) exhibited the highest carbon absorption capacity (−72.53 mg·m−2·h−1), followed by submerged plant + fish + snail (HSXB) and submerged plant + fish (HSX) treatments. CH4 emissions were initially higher in the combined biological treatments but were eventually surpassed by the control group as algal cell density increased. Carbon sink potential and CH4 emissions were strongly correlated with algal cell density and chlorophyll a concentration. While combination treatments (HSX and HSXB) effectively suppressed algal proliferation, the submerged plant-only treatment demonstrated superior nutrient removal efficiency. The findings provide theoretical support for ecologically based management strategies that simultaneously address eutrophication control and carbon sequestration in freshwater ecosystems, contributing to both water quality improvement and climate change mitigation.