Abstract:

To strengthen the comprehensive treatment of groundwater overexploitation and land subsidence in North China, the Ministry of Water Resources initiated a pilot project in 2018, focusing on ecological water replenishment in sections of the Hutuo River, Fuyang River, and Nanjuma River. We monitored phytoplankton and water quality factors from 2019 to 2022 in the Hutuo River and Nanjuma River, which have received ecological water supplement for five executive years (2018-2022), to evaluate the effects of the replenishment and explore phytoplankton community responses. Results indicate that ecological water replenishment gradually improves water quality from inferior-V class to II-class, reaching optimal conditions by the third year. Phytoplankton communities significantly altered in response to changes in environmental factors. Specifically, the density, biomass, percentage of cyanobacterial species, and the dominance degree of dominant species decreased over time, while the percentage of diatom species and density, Margalef index, Shannon-Wiener diversity index, and Pielou index increased. The dominant phytoplankton species shifted from cyanobacteria to diatoms and chlorophytes. Redundancy analysis (RDA) revealed that total nitrogen and pH were the primary environmental factors influencing phytoplankton community structure.

Key words: ecological water supplement, phytoplankton community, dominant species, diversity, Redundancy analysis (RDA)