The water of urban landscape park is often confronted with microalgal blooms due to its stagnancy. Bioremediation using the combined emergent and submerged plants to control the microalgae growth was investigated in the present study. Two water bodies (Bei and Xin) of Yuyuantan Park in Beijing were selected for the field experiments, and the other lakes with different vegetation of macrophytes were selected as the comparison. The concentrations of chlorophyll a (chl a), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP), and water temperature and transparency were monitored before and after bioremediation from 2015 to 2017. Results showed that the effects of microalgal inhibition were more significant 2 years after bioremediation. Specifically, the chl a of Dong Lake without any vegetation of macrophytes was up to 65.1 μg/L in summer of 2017, while the Bei and Xin Lakes was only 6.2 and 11.3 μg/L, respectively. In addition, the water quality and transparency also improved, with water bodies being crystal clear. Submerged plants played major roles in microalgal control and water quality improvement, compared to the lakes with only emergent plants. The intensity of humic acid-like substances in three-dimensional fluorescent spectra was stronger for the lakes with submerged plants.

Still-water ponds in urban parks are often eutrophic; hence, these ponds are typically at risk of algal blooms, which have a negative impact on landscapes and visitor experiences. Instead of adopting the current mainstream methods of ex situ ecological remediation with flowing water bodies, such as the construction of a circulating filtration system or an artificial wetland system around the pond, this research adopted in situ ecological remediation in still-water ponds to suppress algal blooms. The plan was implemented through a small-scale engineering design and plant configuration inside the pond. Using six still-water ponds in Beijing Yu Park as experimental sites, different mini-engineering designs and plant configurations were implemented at different ponds to perform comparative experiments, and the water quality of each pond was monitored for three consecutive years. By summarizing the variation in key water quality indices for each pond, we found that a mini-engineering design of “multilevel” pond revetments and lakebeds combined with a “multilayer” aquatic macrophyte configuration of floating-leaved plants, emergent plants, and submerged plants could effectively inhibit algal blooms. Thus, an effective ecological self-purification model and corresponding landscape design principles for still-water ponds in urban parks were proposed.