Types of zooplankton community and influencing factors in summer in Shuaishui River

In August 2018,we set 19 sampling sites in Shuaishui River which is the biggest tributary of Xin'an River,to collect zooplankton samples and measure in situ physicochemical variables.The results showed that a total of 22 species belonging to 2 families 19 genera were recorded from Shuaishui River.Of them 20 species in 17 genera belong to Rotifera,and 2 species in 2 genera belong to Copepods.There were no Cladocera species found from the river.The abundance of zooplankton in the river was quite low (average value:123 L-1,varied between 7~1 675 L-1).Rotifer contributed most to zooplankton species composition and biomass of the river.Distribution of zooplankton community was not even spatially,and both species richness and abundance of zooplankton in midstream were slightly higher than those in up- and down-streams.Based on species composition,the communities in all the sample sites were clustered and divided into five quite different community types.Zooplankton abundance varied among groups.Water quality assessment results based on the species composition and abundance of indicator species indicated that Shuaishui River was at the level of o-oligomeric pollution or o-beta oligo-middle pollution.Redundancy analysis (RDA) showed that indicators,such as dissolved oxygen (DO),dissolved matters and related variables(TDS:total dissolved solids;Sal:salinity;SpCond:conductivity)and CODMn (chemical oxygen demand) were vital environmental factors affecting zooplankton community