Spatial-Temporal Succession And Ecology Health Assessment Of Plankton Functional Groups In Water Source Ecological Purification System

Yanlong Lake water source ecological purification system uses artificial wetland as the core technology to pre-treat micro-polluted drinking water.Affected by different internal“unnatural”environments and purification processes,plankton habitats has strong spatial and temporal heterogeneity.Based on the characteristics of seasonal changes in the internal environment of the water source ecological purification system,this topic explored the changes of plankton community and the response characteristics of plankton functional groups,and used the Q index to evaluate the ecological health of this system,and discussed its applicability.Not only provides theoretical guidance for the operation and management of the water source ecological purification system,but also provides new ideas for the study of plankton functional groups and Q index.The main research conclusions are as follows:1.Characteristics of plankton habitat changeYanlong Lake is located in Yancheng,Jiangsu Province,with an average temperature of-4.0?~34.7?throughout the year.The rainfall was concentrated in the summer,and the total rainfall was up to 643.5 mm.The winter was cold and dry,and the total rainfall were 53.8 mm.Affected by the concentrated heavy rainfall in summer,the water quality of Mangshe river was poor,belonging to IV water,mainly manifested as:The content of dissolved oxygen was the low,and the average concentration was 3.28 mg/L;The average turbidity of water was 59.11 NTU;The content of nutrients was high,the average concentrations of total nitrogen,total phosphorus and ammonia nitrogen were 1.88 mg/L,0.19 mg/L and 0.88 mg/L respectively,and the average concentrations of permanganate index and five-day biochemical oxygen demand were 5.83 mg/L and 9.19 mg/L respectively.In general,except for some indicators(total nitrogen,total phosphorus and five-day biochemical oxygen demand)exceeding the standard,other indicators basically achieved the class III water standard of surface water environment.The internal water environment of the water source ecological purification system had strong spatiotemporal heterogeneity,among which there were significant spatial differences in dissolved oxygen,pH,turbidity and transparency(P<0.001),while the seasonal differences in water temperature,dissolved oxygen,electrical conductivity,total phosphorus and ammonia nitrogen were the most significant(P<0.001).2.Succession of plankton community and functional groupsDuring the study period,the species of Chlorophyta and rotifers were the most in the water source ecological purification system,accounting for 45.84%and 50.00%of the total species respectively.The dominant FGs in the whole year were B,D,P,MP,X1,J and Lo;the dominant MBFGs in the whole year were GroupI,GroupIV,GroupV and GroupVI;the dominant zooplankton functional group in the whole year was RF.The community structure of the dominant functional groups of plankton in winter was single and changed little,but in summer and autumn it was opposite.The stability of water quality in the water source ecological purification system was reduced:On the one hand,the total algal cell density(6.32×10~5~2.94×10~6 ind/L)and the average concentration of Chl a(12.96~42.55?g/L)increased to 1.53×10~6~3.00×10~6 ind/L and 21.46~55.88?g/L,respectively,which increased the risk of water bloom.On the other hand,phytoplankton diversity decreased,and phytoplankton species decreased by 7 genera at most;The zooplankton community was relatively stable,and the total density of zooplankton in the effluent was 0.99~1.60 ind/L less than that in the inflow,only 3.12 ind/L more in summer.3.Habitat response characteristics of plankton functional groupsThe dominant plankton functional groups could effectively respond to the temporal and spatial changes of water environment in the water source ecological purification system.The main response characteristics were:In winter,FGs(B and P),MBFGs(GroupVI)and zooplankton functional group(RF)responded to the habitat changes of high dissolved oxygen content,pH increase and excessive five-day biochemical oxygen demand concentration respectively;In spring,water temperature was the key environmental factor affecting B,GroupVI,SCC and SC.W1 and W2responded to the change of organic matter concentration.GroupI responded to the environmental change of water turbidity reduction,transparency improvement and underwater light enhancement;In summer,Tc,M and SCC responded to the changes of water temperature and eutrophication.Group?,SCF and RC were sensitive to the changes of turbidity;In autumn,B and Group?indicated the change of pH rise,MCC and RC responded to the increase of concentration of nitrate nitrogen and five-day biochemical oxygen demand respectively,and RF responded to the decrease of water temperature.The results of redundancy analysis showed that MBFGs is better than FGs in habitat response.Among them,water temperature,pH and five-day biochemical oxygen demand were the key environmental factors that affect the succession of MBFGs.4.Water quality evaluation results and Q index applicability analysis of the water source ecological purification systemAccording to the results of three kinds of water quality evaluation,the pollution degree of Yanlong Lake water source ecological purification system was the highest in summer,which was in the state of light eutrophication.In autumn,the water quality was better,the ecological condition was good,and it was in the state of medium nutrition.By comparing the water quality evaluation results of comprehensive nutrition state index,absolute dominant FGs and Q index,the Q index evaluation results of the water source ecological purification system were better than the actual water quality conditions,which was not suitable for evaluating the water quality of the water source ecological purification system.