Restoration of submerged vegetation mitigates internal nitrogen and phosphorus loading in a shallow lake

Abstract

Background and aim

Sediments serve as the primary reservoir for nitrogen and phosphorus nutrients in lakes, and the release of these nutrients plays a crucial role in contributing to lake eutrophication. The restoration of submerged vegetation has emerged as a promising area of lake ecosystem research and is recognized as an effective method for managing eutrophic lakes. However, the validity of previous findings may be compromised by artificial experimental conditions and the brief duration of the studies, potentially underestimating the long-term effectiveness of submerged plants in restoring eutrophic lakes.

Methods

We restored a eutrophic lake through the reconstruction of submerged vegetation. Continuous sampling and monitoring of lake water and sediments were conducted throughout the project. By analyzing the spatiotemporal variations and factors driving nitrogen and phosphorus concentrations in the overlying water and sediments, we explored the effects of the restoration of submerged vegetation on nitrogen and phosphorus loading in the sediment‒water system.

Results

The restoration of submerged vegetation significantly improved the environmental conditions in overlying water in the lake by increasing transparency and dissolved oxygen levels while reducing nitrogen and phosphorus concentrations. Moreover, throughout their growth period, submerged plants could significantly reduce nitrogen and phosphorus loads in surface sediments (0–5 cm), particularly the concentrations of organic nitrogen (ON), ammonium nitrogen (NH₄⁺-N), Ca-bound P (Ca-P), and P bound to Fe, Al and Mn oxides and hydroxides (Fe–P).

Conclusion

Our findings suggest that the restoration of submerged vegetation effectively controlled the nutrient loads of nitrogen and phosphorus in the overlying water and sediments of the lake. To further stabilize and extend the function of submerged plants in controlling internal nutrients and purifying water quality, it is necessary to strengthen the construction of a multi-seasonal and age-structured submerged plant community to promote the benign cycle of the lake ecosystem.

Graphical abstract