Abstract: To clarify metazoan zooplankton community structure and its relationship with environmental factors in Tongzi River, Guizhou Plateau, we investigated metazoan zooplankton and physicochemical variables in August (wet period), November (dry period) in 2020 and April (normal period) in 2021. A total of 35 species were identified, including 28 species of rotifers, 2 species of copepods and 5 species of cladophors. There were 8 dominant species, including Keratella cochlearis, Polyarthra trigla, and Phyllodiaptomus tunguidus. The abundance of metazoan zooplankton was 186.11, 55.33, 176.15 ind·L^-1, while the biomass was 0.25, 0.14, 0.17 mg·L^-1 in the wet, dry and normal periods, respectively. The diversity index showed significant spatial and temporal variations (n=75, P<0.01), with the mean values of Shannon index and Margalef index being 1.02 and 1.03, respectively, indicating that water was at α-medium pollution level. Results of redundancy analysis and principal component ana lysis showed that water temperature, chemical oxygen demand (COD_Mn), and phosphate (PO₄^3--P) were the main environmental factors affecting community structure of metazoan zooplankton. Comprehensive analysis based on dominant species composition, biodiversity index and trophic state index showed that water quality of Tongzi River was at a medium pollution state.

Key words: zooplankton, environmental factor, redundancy analysis, water quality evaluation, Tongzi River.