Stage Variation of Phytoplankton and Environmental Factors in a Large Drinking Water Reservoir: from Construction to Full Operation

Abstract

Temporal and spatial variations of 13 environmental factors and phytoplankton composition were investigated for a drinking water reservoir, from its construction to full operational stages. The studied reservoir has high diversities in phytoplankton with total number of 282 species. The average density of phytoplankton was 2.301 × 107 ind/L (individuals/liter). A canonical correlation analysis (CCA) was carried out indicating that pH, total nitrogen (TN), and temperature; dissolved oxygen (DO) and turbidity (NTU) were the dominant environmental factors; while Microcystis incerta and Tetrachlorella alternans were the dominant phytoplankton. Chemical oxygen demand (CODMn) and total organic carbon (TOC) showed no significant correlation with location and time, while the pH values showed a dependence on location and time. Values of the nutrient elements such as total phosphorus (TP) and NH4 +-N varied over time and location. The density of phytoplankton varied with seasons and presented wave properties at different monitoring stations. Species diversity of the phytoplankton community varied in terms of evenness rather than dominance. Dactlocococcopsis fascicularis, Dictyosphaerium pulchellum, Gloeoactinium limneticum, Chlorella vulgaris,Ulothrix sp., and Cyclotella sp. showed a positive correlation with temperature, turbidity, TP and TN, and a negative correlation with TOC and DO, while Scenedesmus quadricarda, Geminella minor, Chroomonas acuta, Dictyosphaerium enrenbergianum, Fragilria brevistriata, and Synedra acus showed a positive correlation with DO, pH, TOC, and salinity. Risk of algae bloom in the reservoir is more likely to occur during the full operational stage; variations of phytoplankton were influenced mainly by seasonal and spatial conditions rather than by operational stages and environmental factors.