Response of Aquatic Plants and Water Quality to Large-Scale Nymphoides peltata Harvest in a Shallow Lake

Aquatic plant harvest has been widely considered a plant management measure, as it can physically remove the targeted plants quickly and efficiently. Few empirical studies have examined the effects of harvesting on water quality or the aquatic plant community in a complete lake ecosystem. A large area (196 km2) of floating-leaved Nymphoides peltata was harvested in Lake Taihu in 2013. The effects of harvesting on the coverage and biomass of N. peltata and on the submerged plant community were evaluated. The quantities of nitrogen and phosphorus removed by harvesting were calculated. Harvesting caused an immediate reduction in N. peltata coverage, and its coverage in the following year ranged from 29.2% to 95.1%. Wave conditions and interspecific competition were the main factors that influenced the response of the submerged plant community to N. peltata harvesting. Harvesting may favor the dominance of Hydrilla verticillata, which expands quickly at an average growth rate of 53 ± 14 g m−2 day−1. Harvesting a large amount of N. peltata has a positive effect on total nitrogen (TN), ammonium nitrogen (NH3-N), and chemical oxygen demand (CODMn) control but can lead to different consequences (e.g., increase in total phosphorus (TP) and algal concentration).