A Comparative Study On Community Structure Of Benthic Macroinvertebrates In Two Distinctive Streams Of Songhua River In Changbai Mountain Area

River ecosystem composed mainly of river habitats and aquatic communities is affected by natural environmental changes and human activities.In recent years,with the acceleration of urbanization and landuse,the river ecosystem has been destructed,including river habitat deterioration and biodiversity reduction.To deal the contradictions between the exploitation and the protection of natural river ecosystem,series study of the relationship between the human interference and the river ecosystem have become increasingly important.To explore human disturbance on the river habitats and benthic macroinvertebrate communities,field investigation and sampling of two upstream tributaries of the Songhua River in Changbai Mountains area were done in June(wet season)and October(dry season),2014.By comparing the difference in hydrological characteristics,physical and chemical factors and macrobenthos communities between two rivers,we can explore the relationship between benthic animal communities and environmental factors.Research indicates:1.The type of landuse in the North river and South river was woodland,the area of farmland,paddy field and residential land in North River was significantly larger than that in South River,the replacement of North River bank were crops.The South River sediment were mainly pebble,while the North River were mainly sand and gravel.The South River's width,depth,flow velocity and flow rate were greater than the North River,but not significant.2.Comparison of the North River and the South River by physical and chemical factors.The North River's TP and BOD5 in the wet and dry seasons were significantly higher than the South River(P<0.01).In the wet period pH,temperature,EC,DO,turbidity,NH4-N,NO3-N,TN,PO43--P,and COD were also significantly higher than the South River(P<0.01).In the dry season,NH4-N,NO3-N,TN,COD were not significant.This indicated that the North River was affected by agricultural activities during the wet period.3.The present study collected 35360 macrobenthos,belonging to 4 phylums,7 classes,14 orders,50 families and 121 taxas.The North River's species richness,density and diversity were lower than the South River.The comparative study of dominant groups and functional feeding groups of the North River and South River indicated that both of them had common species in the same period,such as: Glossosoma sp.,Gammarus sp.in the wet season;and during the dry season,Ephemerella sp.,Suwallia sp.,Gammarus sp.were the commom species.The grather-collectors in both of the North River and South River had the absolute advantage,with the largest density relative abundance.4.The analysis of the relationship between benthic animal community structure and environmental factors of two features rivers showed that there were differences between the North and South river about the main environmental factors which affected benthic animals.The main environmental factors in South River were width and pH in the wet season and temperature and dissolved oxygen in the dry season.While in North River,nitrate,turbidity,temperature,total phosphorus and sand were the main environmental factors in the wet season,temperature,pebbles,dissolved oxygen,nitrate,redox potential and total nitrogen in the dry season.