Characteristics Of Plankton Community Structure And Aquatic Ecosytem Health Assessment In Autumn In Qin River Of Jincheng Region

As the largest river in Jincheng region,Shanxi Province,China,Qin River provides water resources for industrial and agricultural activities.Water pollution in Qin riverwill influence water safety of industry and agriculture in Jincheng city.Water pollution was found from previous studies,whereas aquatic organisms and aquatic ecosystem health are still unknown in Qin river in Jincheng region.Thus,surface water quality and plankton in 61 sampling sites in Qin river in Jincheng region were investigated and analyzed in October 2020.Firstly,the characteristics of plankton communities including species,density,diversity and biomass were analyzed in Qin River in Jincheng region.Then,the relation between environmental factors including water quality varialbles and land use proportions at 300m buffer and the abundance of plankton species were explored by canonical correspondence analysis（CCA）.Finally,an IBI based on plankton（P-IBI）was constructed to assess health of the Qin River.The results of the study were as follows:（1）A total of 7 phylum 47 species of phytoplankton were identified in Qin River in Jincheng region,Bacillariophyta accounting for 46.8%of all species.The species of the phytoplankton in Qin River were mainly composed of the Chlorophyta and Bacillariophyta,and in the Dan River the species were mainly composed of the Bacillariophyta.The density and biomass of phytoplankton in middle-lower reaches of Dan River was significantly higher than other sites.The dominant species in Qin River and Dan River were different.The dominant species in Qin River were included:C.erosa,C.acuta,C.vulgaris.The dominant species in Dan River were included:C.erosa,F.vulgaris,E.viridis,C.vulgaris,T.oblonga Lemm and C.stelligera.The mean value of Shannon-Wiener diversity index（H’）in Qin River in Jincheng region was 1.41,and the mean Pielou evenness index（J）was 0.68,the values of H’and J in Qin River were higher than those in Dan River.（2）A total of 4 phylum 37 species of zooplankton were identified in Qin River in Jincheng region,Rotifera and Protozoa accounting for 46.8%and 32.4%,respectively.The density and biomass of zooplankton in middle-lower reaches of Dan River was significantly higher than other sites.The dominant species in Qin River and Dan River were different.The dominant species in Qin River were included:A.vulgaris,D.globulosa,D.pyriformis.The dominant species in Dan River were included:A.vulgaris,D.globulosa,C.strennus and Nauplius.The mean value of Shannon-Wiener diversity index（H’）in Qin River in Jincheng region was 1.28,and the mean value of Pielou evenness index（J）was 0.89.The values of H’and J in Dan River and the upper-middle reaches of Qin river were relatively high.（3）The results in Qin River by a canonical correspondence analysis（CCA）showed that CODcr,TP,water temperature,SO₄^2-and the percent of forest area at 300 m buffer were the main factors affected the phytoplankton in Qin River.C.vulgaris,C.erosa and C.acuta were significantly positive correlated with NO₃^-,cultivated land and residential land proportions at 300 m buffer.Cl^-、COD_cr、NO₃^-、cultivated land and urban land proportions were the main factors affected the phytoplankton in Dan River.C.erosa,C.stelligera and T.oblonga Lemm were significantly positive correlated with COD_cr and Cl^-,F.vulgaris and C.vulgaris were significantly positive correlated with NO₃^-and cultivated land proportions,E.viridis was main influenced by the percent of urban land at 300 m buffer.The CCA analysis showed that the main factors affected the zooplankton in Qin River in Jincheng region were Cl^-、TN、NO₃^-and water temperature.D.globulosa,A.vulgaris and D.pyriformis were mainly affected by NO₃^-、NH₄⁺-N and COD_cr.C.strennus and Nauplius were significantly positive correlated with Cl^-and SO₄^2-.（4）A plankton integrity index（P-IBI）based on density,biomass,diversity and nutritional status was established for river health evaluation.Sites with“Excellent and Good”and“Poor and Very poor”status accounted for 26.2%and 49.2%,respectively.“Very poor”sites were mainly located in the Dan River,“Poor”sites were mainly located in the middle reaches of the Qin River and upper-middle reaches of the Dan River.Significantly negative correlations between Cl^-,SO₄^2-,F^-and P-IBI indicated that the P-IBI might reflect domestic and industrial wastewater pollution in the Qin River.The P-IBI strongly differentiated reference and impaired sites,suggesting the suitability of the index in Qin River.