Community structure characteristics of zooplankton in main freshwater rivers of Jiangmen City, Guangdong Province

In order to understand the community structure of zooplankton in the main freshwater rivers of Jiangmen, Guangdong Province, we investigated the zooplankton community structure in Tanjiang River, Yinzhou Lake and Xijiang River from December 2016 to October 2017. Altogether 157 species of zooplankton had been observed, including 74 species of rotifers, 43 species of protozoa, 21 species of cladocers and 19 species of copepods. The annual average density and biomass of zooplankton were 1 651 and 0.80 mg·L⁻¹, respectively. The density of protozoa was the highest (1 164 ind·L⁻¹). And the highest biomass of rotifers and copepods was 0.37 and 0.31 mg·L⁻¹, respectively. Compared with the historical level, the species number of large zooplankton had decreased significantly, while the small zooplankton had increased significantly. And the density of zooplankton increased significantly, while their biomass decreased significantly. The Shannon-Wiener diversity index H' was 1.05−4.36, and the Pielou index J' was 0.23−1.15. There were 30 dominant species in the survey area, and the number of protozoa was the largest (15 species). Among the dominant species, 10 were eutrophic indicator species, all of which were rotifers. Dominant species of the indicator species for eutrophic water were only distributed in Tanjiang River and Yinzhou Lake, indicating that Xijiang River water quality is the best.