Submersed macrophyte restoration with artificial light-emitting diodes: A mesocosm experiment

Area of Science:

• Aquatic Ecology
• Restoration Ecology
• Environmental Science

Background:

• Urban lakes face stressors impacting submerged macrophytes, crucial for water clarity.
• Impaired underwater light conditions are a key factor in macrophyte decline in urban lakes.
• Restoring macrophytes is vital for improving urban lake ecosystems.

Purpose of the Study:

• To investigate the effectiveness of artificial light enhancement using light-emitting diodes (LEDs) for restoring submerged macrophytes in urban lakes.
• To assess the impact of varying LED light intensities on the growth of tape grass (Vallisneria natans).

Main Methods:

• Twelve 1000 L mesocosms were used, planted with Vallisneria natans.
• Treatments included a control and three artificial light intensities (10, 50, 100 µmol m⁻² s⁻¹).
• Measurements over three months included plant growth metrics, phytoplankton, and periphyton chlorophyll a.

Main Results:

• The highest light treatment (100 µmol m⁻² s⁻¹) significantly increased leaf number, leaf length, shoot number, and biomass compared to the control.
• Periphyton chlorophyll a increased with plant growth but did not inhibit macrophyte development.
• Phytoplankton chlorophyll a remained low and was not correlated with plant growth.

Conclusions:

• LED light supplementation can facilitate the growth of Vallisneria natans under eutrophic urban lake conditions.
• This method shows potential for urban lake restoration, particularly in the absence of fish.
• Further lake-scale studies are needed to evaluate LED effectiveness considering natural stressors.