Different Life Forms of Macrophytes Have Different Effects on Lake Water Quality and Carbon Sequestration

Numerous studies have confirmed that macrophytes contribute to improving water quality; however, it remains uncertain whether they can enhance lake carbon sequestration. We conducted a mesocosm experiment to compare six macrophyte species categorized into three life form groups: submerged, floating-leaved and emergent. The results showed that the concentrations of total phosphorus and total organic carbon in water were significantly lower in the submerged macrophyte group than in the other groups (p < 0.05). The sediment total phosphorus and sediment total carbon in the emergent macrophyte group were lower than those in the other groups. Plant tissue phosphorus in the submerged macrophyte group was significantly higher, while plant tissue carbon was significantly lower than in the other macrophyte groups (p < 0.05). Although the emergent macrophyte group released the highest CH4 flux, it absorbed the most CO2, resulting in a significantly lower CO2-equivalent flux. Submerged macrophytes had a higher specific leaf area but a lower leaf area index and specific root length; floating-leaved macrophytes recorded a higher root mass ratio, total biomass, and relative growth ratio; meanwhile, emergent macrophytes had a lower root mass ratio. It is therefore recommended to configure macrophyte communities differentially based on specific restoration objectives.