INVESTIGATION ON PLANKTON COMMUNITY COMPOSITION AND WATER QUALITY STATE IN THE MAINSTREAM OF XIANGJIANG RIVER

To evaluate tropic state and biotic community of the main stream of Xiangjiang River, the water quality and plankton distribution were sampled and analyzed from 2010 to 2011. The plankton community characteristics of Xiangjiang River were studied via Shannon-Wiener index, and nutrient level was assessed in association with physicochemical index of water quality. The results showed that, a total of 164 species of the phytoplankton belonged to 99 genus; the total cell density varied from 1.83104 to 51.1104 cells/L; the biomass ranged from 0.03 to 0.60 mg/L. The species of zooplankton was 80 species, and the average abundance varied from 2.16 to 76.34 ind./L; the biomass ranged from 0.01 to 1.95 mg/L. The phytoplankton diversity index were 2.47-5.43, while the zooplankton ones were 1.63-3.38. The plankton diversity showed that the plankton community of Xiangjiang River in a stable state. From the analysis of the species and community composition of the m-m indicated species, it was found that the water quality of the Xiangjiang River belonged to the ecological middling pollution type. According to the comprehensive trophic level index (TLI), the values of Xiangjiang River were between 38.27 to 51.97, and the average was 43.73. It showed that the river was in a mesotrophic level. The results showed that the water quality of Xiangjiang River is bad, but has no obvious trend to the eutrophication by chemical and biochemical evaluation.