Apreliminary Study On Macroinvertebrates Community Characteristics In A Headwater Stream Of Changbai Mountain

Macroinvertebrates are one of the important parts of the river ecosystem.Since located in the middle of the food chain,macroinvertebrates affect the material cycle and energy flowing process so directly,that the ecological research of macroinvertebrates community has been one of the hot topics.Changbai Mountain is not only the highest mountain in Northeast China,but also the source of the Songhua River,the Yalu River and the Tumen River.And Changbai Mountain is an important natural resources treasure with abundant species and high biodiversity,too.By now,domestic researches on macroinvertebrates in the headwater streams of Changbai Mountain have been relatively rare,which were mainly carried out in 1990 s.Research in this paper focused on the macroinvertebrates community of Songjiang River which is one of the headwater streams of Changbai Mountain.Investigation and sampling in August 2015 and August 2016 in the research area,and the relevant environmental parameters were also measured.To answer these following scientific problems: 1)What are the characteristics of the macroinvertebrates communityin Songjiang River? 2)What are the main environmental factors influencing macroinvertebrates community? 3)What is the health status of Songjiang River? Which bio-assessment index is more suitable for biological evaluation of water quality in Songjiang River? The main conclusions are as follows:(1)During the study period,a total of 4933 macroinvertebrates were collected from Songjiang River,belonging to 3 phylum,6 class,14 orders,41 families and 96 genera(species),among which aquatic insects including the EPT species and the larvaes of Diptera were the most,accounted for 92.86%.Glossosoma sp.,Baetis sp.,Chaetocladius sp.,Dicranomyia sp.,Epeorus sp.,Orthocladius sp.were dominant species in Songjiang River.The average density of macroinvertebrates in 2016 was obviously higher that than in 2015(p< 0.05),which were 1720.99 ind./m2 and 396.81 ind./m2 respectively.Among these macroinvertebrates,aquatic insects contributed most.The biodiversity of the macroinvertebrates community of Songjiang Riveris relatively high,but different sampling sites differed significantly.Collector-gathersaccounted for an absolute advantage of the functional feeding groups,in the contrast,shredders and filter-collector only accounted for a small part or even didn't exist in some sampling sites.(2)CCA analysis indicates that the environmental factors influencing macroinvertebrates community structure didn't remain the same in different years.Dominant environmental factor in 2015 was river flow velocity,followed by altitude,river width and canopy density.While in 2016 the most important factor was river width,which was followed by substrate smaller than 1mm,ammonia nitrogen and total nitrogen.(3)The health status of Songjiang River which is one of the headwater streams of Changbai Mountain was overall good.Among all the sampling sites,the sites in the “healthy” conditions were the most,accounted for 50.00%;the sites in the “sub-healthy” and “general” conditions accounted for 34.38% and 15.62% respectively.There were no sites in “poor”or“very poor” conditions.ASPT scoring system in this study had poor sensitivity,so it didn't suit for biological evaluation in the area.Comparatively speaking,Shannon-Winner index and BMWP index were more suitable for biological evaluation of water quality in this region.