Investigation Of The Macrobenthos Community Structure And Predators Of Blackfly Larva In The Irtysh River Tributaries

The outbreak of black flies in the Irtysh River Basin has affected the life of the local military and civilians.The local government mainly relies on chemical pesticides for prevention and treatment,resulting in little success and many ecological problems.Controlling the population density of larvae by the natural enemies of macrobenthos is a new direction for the control of black flies.Therefore,in this study,surveys were carried out on the community structure of macrobenthos and the natural enemies of the larvae of black fly in the Irtysh River tributary from June to September in 2017,in order to provide evidences for the protection of benthic biodiversity and the prevention of blackflies.The results are as follows:1.Community structure of the macrobenthos in the tributaries of the Irtysh River: a total of 40 species of macrobenthos animals were collected in the tributaries of the Irtysh River,mainly belonging to molluscs,arthropods,and annelids;The average biomass of the animals is 1.02g/m2,and the inhabiting density is 767.8 ind./m2.The dominant species of macrobenthos animals in the Irtysh tributary(referring to the dominance degree greater than 0.02)are: Simuium sp.,Baetis sp.,Brachycentrus sp.,Heptagenia sp.,and Hydropsyche sp.,their dominance degrees are of 0.602,0.092,0.047 0.042 and 0.031,respectively.2.Diversity analysis of macrobenthos: the Shannon-Wiener index(H)is 2.393,the Margalef index(D)is 3.068,and the Pielou index(J)is 0.450.Their change intervals are 0.774 to 3.038,0.471 to 1.331 and 0.488 to 0.878,respectively.The results show that in the tributaries of the Irtysh River the species distributed evenly,and species composition and richness are simple.3.Pearson correlation analysis of macrobenthos and various physicochemical factors in the study area: The spatial distribution of macrobenthic animals in the Irtysh River tributaries is related to electrical conductivity,dissolved oxygen and elevation.There is a very significant negative correlation between species and electrical conductivity,and a highly significant positive correlation between habitat density and dissolved oxygen.4.There are 31 species natural enemies of the larvae and pupa of black flies in this investigation,belonging to the Insecta(Diptera,Trimonoptera,Acarina,Coleoptera,Thysanoptera,Hemiptera,Acarina),Crustacea,Gastropoda,Bivalvia,and fish.The main natural enemies are fish,mollusks,crustaceans,and insects.Among the predatory insects,such as the larva of Pelicans,Chironomididae,Polygonidae,Cyclodidae,Cyclodidae,Polygonidae,and Polygonidae,and in particular Hydropsychilda and Ephemeroptera are the main natural enemies of larva of black flies.Correlation analysis results show that there is a significant correlation between the number of larvae and their natural enemies.