Variation Characteristics Of Water Environment And Plankton Community In Ponds Of Juvenile Chinese Mitten Crab In Sandy Areas Of Taixing

Eriocheir sinensis,also known as crab,its aquaculture has become a major branch of China’s aquaculture industry.Yaowang town of Taixing city is located in the area of high sandy soil,which contains more sand,is easy to leak,and the soil fertility is poor.Traditional river crab culture has higher density,higher yield,smaller individual size,more nitrogen and phosphorus emissions,low economic benefits,easy to cause water eutrophication.But the breeding of young crabs in Yaowang sandy land area of Taixing adopts an ecological model to provide sufficient habitat for crabs.The aquaculture water environment is better,so that it also has the excellent appearance characteristics of crabs in the Yangtze River Basin,which not only has better economic effects,In addition,the breeding process has little impact on the surrounding water environment and has a certain ecological effect.This study aims to explore the change characteristics of pond water environment and plankton community during juvenile crab breeding in the high sandy area of Yaowang,Taixing We monitoring the water quality and water source in three ponds from June to October in 2018 at Jiangsu Taixing Jiangyuan Agriculture and Animal Husbandry co.LTD.Two groups were set in this experiment,one of them is water source group and the second is young crab ponds group.Water quality monitoring has been conducted in two groups,which including Including 10indicators such as p H,and conduct a sampling survey of its plankton.Explore the characteristics of pond water environment changes and changes in indicators such as density during the breeding period of juvenile crabs in high sandy soil.After experimental analysis and summary,scientifically evaluate the water environment health of juvenile crab ecological breeding ponds in high-sandy land areas,this expirement to provide a theoretical basis for the sustainable development of the"high-sandy soil"model in this area.1.Impact of Eriocheir Sinensis culture on water environment in sandy areas of Taixing citythere is no significant difference of T,p H and DO between crab pondsand water source（P>0.05）.The difference of NO₂^--N between crab ponds and water source were significant（P<0.05）.The levels of NH₄⁺-N,NO₃^--N and TN in the water source was generally higher than those in crab ponds,and levels of COD_Mn,PO₄^3--P and TP in the water source was generally lower than those in crab ponds.The COD_Mn,TN and TP inⅢstandard of surface water environmental quality standard lower than those of young crab ponds,but the ponds were in line with the first-class standard for tailwater discharge requirements for pond culture.The aquaculture tail water will be directly discharged to the outside without treatment,and will eventually flow into the canal,which will not cause pollution to the water body.2.Community structure characteristics of zooplankton in Eriocheir Sinensis ecological cultivation ponds in sandy areas of Taixing citywe identified 52 species of zooplankton totally in these two grous.A total of 52 species of zooplankton were identified in the water source group and the juvenile crab ponds group,and the number of species of rotifers,cladocerans and copepods were 22,17,and 13 respectively.The average density of young crab pond rotifers,cladocerans and copepods varies from 91 to 871 ind/L,55 to 326 ind/L and86 to 364 ind/L,respectively water-sourced rotifers,cladocerans and copepods The range of class density is 74～538 ind/L,57～269 ind/L and 74～286 ind/L.The average biomass of young crab pond rotifers,cladocerans and copepods varied in the range of 0.018～0.703 mg/L,2.373～23.472 mg/L and 3.865-16.576 mg/L;water-sourced rotifers,cladocerans and copepods The variation range of foot biomass was0.013～0.329 mg/L,1.219～18.641 mg/L and 3.118～12.723 mg/L.The values of H’,J and D of zooplankton in young crab breeding ponds ranged from 3.068 to 4.089,from 0.742 to 0.831 and from 2.850 to 4.172,respectively.The H’,J and D values of water zooplankton ranged from 3.257 to 4.052,0.729 to 0.862 and 3.194 to 4.433, respectively.The water quality of young crab ponds and water source can be classified into light pollution stage based on physical and chemical indexes and zooplankton diversity index respectively.3.Community structure characteristics of phytoplankton in Eriocheir Sinensis ecological cultivation ponds in sandy areas of Taixing citywe identified 105 species of 53 genera and 8 phyla of phytoplankton totally.The number of species of green,siliceous,blue,naked,methyl,cryptic,gold and xanthophyta were 46,23,15,11,5,3,1 and 1,respectively.we found 10dominant species,divided into 7 functional groups.According to the classification method of phytoplankton functional group,the dominant species can be divided into7 functional groups:C,L_o,W_o,X1,J,B,MP.The average density and average biomass of phytoplankton in juvenile crab ponds varied from 9.142×10⁶ to31.581×10⁶ cell/L and 9.273 to 28.457 mg/L;the water source phytoplankton density and biomass varied from 8.795×10⁶ to 28.673×10⁶ cell/L,respectively and8.692～26.821 mg/L.The variation ranges of H’,J and D values of phytoplankton in young crab breeding ponds were 3.658 to 4.428,0.631 to 0.741 and 2.859 to 3.912,respectively.The H’,J and D values of water phytoplankton ranged from 3.579 to4.267,0.657 to 0.753 and 3.087 to 3.552,respectively.After RDA analysis,it can be concluded that temperature,for the reproduction of phytoplankton functional groups,N,P and p H are the limiting factors.Based on the physical and chemical indexes of water quality and the phytoplankton H’,J and D indexes,the water quality of young crab ponds and water sources can be classified into light pollution stage.Based on the above three experiments,it can be concluded that the various water quality indicators of juvenile crab ponds basically meet the standards,the plankton community structure is more complex,and the juvenile crab pond ecosystem is relatively stable,which can meet the normal growth of juvenile crabs.