Macrophyte Restoration Promotes Lake Microbial Carbon Pump to Enhance Aquatic Carbon Sequestration

Macrophyte-based lake restoration has successfully transitioned lakes from turbid conditions dominated by phytoplankton to a more natural, clear state; however, its impact on microbial carbon pump-mediated dissolved organic carbon (DOM) storage and greenhouse gas (GHG) emissions in the aquatic ecosystem remains largely unexplored. Through a year-long field study, we conducted a comparative analysis of two alternative habitats within the same lake-restored and unrestored areas. Results demonstrated that restoration not only substantially decreases nutrient levels and algal blooms-evidenced by over 50% reductions in nitrogen, phosphorus, and chlorophyll a-but also significantly increases the accumulation of recalcitrant DOM. This is characterized by rises of 9.52% in highly unsaturated compounds, 8.68% in carboxyl-rich alicyclic molecules, 37.54% polycyclic condensed aromatics and polyphenols, and 20.21% in SUVA₂₅₄. Additionallly, key microbial taxa with potent carbon pump functions-primarily Gammaproteobacteria, Alphaproteobacteria, and Actinobacteria-are enriched in restored areas. Structural equation modeling (SEM) further elucidated the complex interrelationships within more pristine lake ecosystems: macrophytes and elevated dissolved oxygen (DO) concentrations enhance carbon sequestration via microbial carbon pump pathways, while the restoration significantly mitigates methane emissions caused by eutrophication. These findings highlight an extra function of aquatic macrophyte restoration, offering valuable insights into microbial processes for future restoration efforts aimed at promoting sustainable aquatic ecosystems and mitigating global warming.