Reservoir regulation-induced variations in water level impacts cyanobacterial bloom by the changing physiochemical conditions

• Published in: Water research (Oxford) 2024-08, Vol.259, p.121836, Article 121836
• Main Authors: Li, Yuan, Fang, Lingchao, Cao, Guangrong, Mi, Wujuan, Lei, Cheyenne, Zhu, Kai, Bi, Yonghong
• Format: Article
• Language: English
• Subjects: algae; biomass; Chlorophyceae; Cyanobacteria; Cyanobacterial bloom; ecosystems; extinction; hydrodynamics; Nutrient cycling; phytoplankton; Phytoplankton community; total nitrogen; total phosphorus; water; Water level; Water regime
• ISSN: 0043-1354; 1879-2448; 1879-2448
• DOI: 10.1016/j.watres.2024.121836

•Changes in water regimes influence algal blooms by field reservoir regulation experiments.•Water level decline and increased velocity correlated with algal biomass reductions.•Dominant phytoplankton community changed from Cyanobacteria to Chlorophyceae.•Water level fluctuations lead to a 50–57 % reduction in cyanobacterial blooms.•Hydrodynamic management helps mitigate ecological impacts of algal blooms. Gaining insight into the impact of reservoir regulation on algal blooms is essential for comprehending the dynamic changes and response mechanisms in the reservoir ecosystem. In this study, we conducted a comprehensive field investigation linking physiochemical parameters, and phytoplankton community to different water regimes in the Three Gorges Reservoir. Our aim was to explore the effects of reservoir regulation on the extinction of cyanobacterial blooms. The results showed that during the four regulatory events, the water levels decreased by 2.02–4.33 m, and the average water velocity increased 68 % compared to before. The average total phosphorus and total nitrogen concentrations reduced by up to 20 %, and the cyanobacterial biomass correspondingly declined dramatically, between 66.94 % and 75.17 %. As the change of water level decline increasing, there was a significant increase of algal diversity and a notable decrease of algal cell density. Additionally, a shift in the dominant phytoplankton community from Cyanobacteria to Chlorophyceae was observed. Our analysis indicated that water level fluctuations had a pronounced effect on cyanobacterial extinction, with hydrodynamic changes resulting in a reduction of cyanobacterial biomass. This research underlined the potential for employing hydrodynamic management as a viable strategy to mitigate the adverse ecological impacts of cyanobacterial blooms, providing a solution for reservoir's eco-environmental management. [Display omitted]