Aquatic Biodiversity And Water Ecological Health Assessment Of Muling River Basin

Muling River Basin is located in the Sanjiang Plain Agricultural wetland ecological area of Heilongjiang Province,surrounded by cultivated land.Muling River has experienced sand digging activities for a long time,and its riverbed has been seriously damaged.In recent years,due to the aggravation of agricultural non-point source pollution,industrial discharge pollution and urban living pollution in Muling River Basin,the water quality has been deteriorating,which has had a negative impact on the production and life of local people.In this study,environmental factors and aquatic community structure and functional groups of Muling River were investigated in May(spring),July(summer)and September(autumn)of 2015 and 2017.During the investigation,83 species and varieties of phytoplankton belonging to 43 genera and 7 phyla were found in Muling River Basin,with abundance between 3.6 × 104 to 1.3 × 107 ind./L and biomass between 0.03?23.21 mg/L.17 functional groups of phytoplankton were divided,the dominant functional groups were F,M,MP,P AND Y,and the seasonal succession was M+P?F+MP+P?+MP+P?M?M+Y?M+MP+ P.The environmental factors affecting phytoplankton functional groups include NTU,ORP,EC and NO3--N.There are 36 species belonging to 27 genera in 4 classes of zooplankton,with abundance ranging from 0.4 × 104 to 1.6 × 108 ind./L and biomass ranging from 0.01 to 16.68 mg/L.Seven zooplankton functional groups were divided,the dominant functional groups were PF,RF and SCF,and the seasonal succession was PF+RF+SCF?PF+RF?P?PF+RF?PF+RF?PF+RF?PF+RE.The environmental factors affecting zooplankton functional groups include NTU,EC,WD,SD and TP.There are 4 phyla,13 orders,46 families,158 genera/species of benthos,with abundance ranging from 9.23 to 353.3 ind./m2 and biomass ranging from 1.08 to 880 g/m2.Six functional groups of benthos were divided.The dominant functional groups were PR,GC and SC.the seasonal succession was GC+SC?PR+GC?PR+GC?PR+GC?PR+GC+SC?PR+GC?PR+GC.The environmental factors affecting the functional groups of benthos include DO,T,TN,NH4+-N and CODMn.There are 46 species in 12 families of 5 orders of fishes,with abundance between 2 and 97.92ind./m 3 and biomass between 8.22 and 770.36 g/m3.Seven fish functional groups were divided,the dominant functional groups were in,PH,BE and OM,and the seasonal succession was IN+BE?IN+BE+OM?IN+PH+BE+OM?IN+BE?IN+BE?IN+PH+BE+OM?IN+BE+OM.The environmental factors affecting fish functional groups include WD,SD,NTU and CODMn.The water quality of Muling River was evaluated by Shannon-Weaver diversity index(H'),Pielou evenness index(J')and Margalef richness index(d),and the results were consistent.The water quality of S1,S2,S3,S4 and S5 sampling sites were best in o-light pollution state.From the average value,the water quality of Muling River Basin is in ?-medium pollution state.The water ecological health assessment system of Muling River Basin is established by AHP,including river water environment factors,river water form quality and river ecosystem services,covering physical factors,chemical factors,river hydrology,river structure,biodiversity and social service functions,with a total of 27 indicators.The coupling effect of each subsystem is very good,the coupling degree reaches the maximum coupling,and the coupling coordination degree rises from primary coordination to intermediate coordination.The main obstacle factors of target layer and criterion layer are river ecosystem service and biological functional group diversity,and the main obstacle factors are phytoplankton functional group diversity,dissolved oxygen concentration and ecological runoff.By calculating the comprehensive index of water ecological health in Muling River Basin,the wehci values in each season are 0.4177,0.4428,0.5071,0.4699,0.4799 and 0.6434,respectively.The water ecological health classification rises from level ? to level ?,and the health status rises from the general level to the sub-health level.The overall trend is rising,the average value is 0.4935,the health classification is level ?,and the health status is general.Generally speaking,the water ecological health level of Muling River Basin is the highest in autumn.