Phytoplankton diversity and water quality bioassessment in typical drinking water reservoirs of the East China region

To investigate the phytoplankton community structure and current water quality status in drinking water reservoirs of East China, this study conducted a sampling survey on the hydro-environmental characteristics and phytoplankton community composition in the Changzhao Reservoir, a typical drinking water reservoir in the East China region. Pearson correlation and redundancy analysis (RDA) identified key environmental drivers, while the comprehensive trophic state index (CTSI) and diversity indices (Shannon-Wiener H ′, Margalef D ) assessed water quality. Results showed phytoplankton comprised 47 genera from six phyla, dominated by Bacillariophyta (86.11%–98.29% relative abundance). Cell density (26.04 × 10 4 –60.01 × 10 4 cells·L −1 ) and biomass (908.49–1701.70 μg·L −1 ) peaked at tributary-reservoir confluences, followed by reservoir tail and dam areas. CTSI indicated mesotrophic conditions at all sites, while H ′ and D suggested light pollution. Integrated evaluation classified the reservoir as lightly polluted to moderately eutrophic. Nitrogen nutrients, chlorophyll-a, and COD Mn were key factors influencing community dynamics.