Abstract:

The species composition and biodiversity of phytoplankton and zooplankton across two seasons (wet and dry periods) and 4 drinking water reservoirs (Tongjiqiao Reservoir, Andi Reservoir, Shafan Reservoir, and Jinlan Reservoir) were investigated to provide a scientific basis for aquatic ecological health and fishery management in Jinhua City. 57 phytoplankton species belonging to 24 families and 7 phyla were identified, with green algae and diatoms being predominant. Zooplankton comprised 19 species across 4 major taxa, dominated by cladocerans and copepods. The abundance and biomass of phytoplankton ranged from 0.215×10⁵ to 19.267×10⁵ cell·L^-1 and 0.826×10^-2 to 36.312×10^-2 mg·L^-1, respectively, while those of zooplankton ranged from 0.25 to 38.25 ind·L^-1 and 0.018×10^-3 to 544.875×10^-3 mg·L^-1, respectively. Both phytoplankton and zooplankton exhibited seasonal fluctuations in abundance and biomass, which were closely associated with the distinct seasonal variations within the reservoirs. The Shannon-Weaver diversity index, Pielou evenness index, and Margalef richness index of phytoplankton were significantly (p<0.05) different across seasons and reservoirs, while the inverse results were found in zooplankton. Our findings further indicated that the proportion of Cyanobacteria in Tongjiqiao Reservoir was notably high, raising concerns about the potential risk of cyanobacterial blooms. Moreover, the relatively low abundance and biomass of plankton across all reservoirs may be attributed to intense grazing pressure exerted by silver carp and bighead carp. Hence, it is recommended that a reasonable harvesting of silver carp and bighead carp will help to maintain the safety of drinking water quality.

Key words: drinking water reservoirs, phytoplankton, zooplankton, biodiversity, water purification fishery