370 / 2024-02-29 22:32:56

Control of cyanobacterial bloom by reservoir regulation: evidence from the Three Gorges Reservoir

Reservoir regulation; water level; phytoplankton; water bloom; Three Gorges Reservoir

Understanding the effects of reservoir’s regulation on algal blooms is essential due to mounting evidence from hydraulic engineering has documented the associations between water regime and increased algal blooms. A field investigation in the Three Gorges Reservoir was conducted to reveal the association between reservoir operation and algal blooms extinction. The corresponding hydrology, nutrient, and phytoplankton characteristics under different water regime were screened synchronously. Data in the Xiangxi River from January 2017 to December 2020 showed that phytoplankton were generally dominated by Cyanophyta, Bacillariophyta and Chlorophyta. Cyanophyta were dominant during the flood period, while Bacillariophyta were dominant during the high water level period. Water level showed significant influence on phytoplankton, effects of the indirect effects (dilution and mixing effect) were greater than that of the direct effects (nutrient concentration, underwater light conditions and water physical factors). Data in the Xiangxi River and Xiaojiang River from June to August in 2021 and 2022 showed that the water level fluctuation could cause the more significant effects on algae blooms restrain.  It could be concluded that change of suspended particles, nutrient cycling, and phytoplankton community mediated by water level fluctuation had regulated phytoplankton community and constrained algal blooms. these findings could deepen our understanding of the ways water level affect phytoplankton in the Three Gorges Reservoir.