| The Baihe River is a first-order tributary of the Yellow River source area,this study used planktonic animals as indicator organisms to investigate and analyze the physical and chemical factors of planktonic animals and water bodies at 36 sampling points in the main and tributaries of the Baihe River Basin and oxbow lake in September 2019(normal water period)and June 2020(flood water period).The research results are as follows:1)A total of 105 species of zooplankton were identified in the two surveys,including 26 species of protozoa,54 species of rotifers,17 species of cladocerans and 8 species of copepods.On the temporal scale,the number,density and biomass of zooplankton species were significantly higher in the normal water period than in the flood water period;on the spatial scale,the number,density and biomass of zooplankton species were highest in the oxbow lake,much higher than in the dry tributaries.The results of redundancy analysis indicated that chlorophyll a,chemical oxygen demand and flow velocity were the main environmental factors affecting the zooplankton community during normal water period,while chlorophyll a,flow velocity and nitrite nitrogen were the main environmental factors affecting the zooplankton community during flood water period.2)The zooplankton in the Baihe River Basin are divided into 7 functional groups:protozoas filter feeders(PF),protozoas carnivora(PC),rotifers filter feeders(RF),rotifers carnivora(RC)small copepods and claocera filter feeders(SCF),small copepods and claocera carnivora(SCC),and middle copepods and claocera carnivora(MCC).The main zooplankton functional groups are PF and SCF during normal water period;The main zooplankton functional groups are PF,MCC,and RC during flood water period.The zooplankton functional group of the main and tributaries of the Baihe River shows a variation pattern of PF+SCF→PF+MCC from normal water period to flood water period,while the oxbow lake shows a→RC+MCC.The results of Mantel test and RDA analysis indicate that chlorophyll a,pH,and dissolved oxygen are important water environmental factors affecting zooplankton communities.3)Based on the water quality status of 36 sampling points in the Baihe River Basin,a comprehensive water quality score was calculated,and reference points were determined in different periods(14 in normal water period and 15 in flood water period).After distribution range analysis,discriminant ability analysis,and correlation analysis,the biological integrity index of zooplankton in the Baihe River Basin was constructed.The Z-IBI index was calculated using the three-method,four-method,and ratio method to obtain the Z-IBI evaluation standard.The evaluation results showed that the temporal pattern of water body health status showed that normal water period>flood water period;The spatial pattern is manifested as main tributary>oxbow lake. |
