Macrobenthic Community Structure Of Spatial And Temporal Distribution Characteristics And Environment Indication In Dongjiang

Macrobenthos were widely distributed in the river ecosystem, their growth,reproduction, and community dynamics were closely related to environmentalfactors （including hydrological characteristics, physical and chemical indicators andriverbed conditions, the river band type, etc.）. Due to its relatively long life, limitedmigration ability, and easiness of be collected, macroinvertebrates were goodindicators in the aquatic ecosystem biomornitoring. Dongjiang is a typical highlyfunctional river in subtropical climatewhich showed strong regional feature in itsorganism community and ecosystem character. Very few study was focused onmacroinvertebrate in this kind of river. Study the macroinvertebrate community willcontribute a lot to both the river ecology and practical application of river ecology,especially to the biodiversity protection of rivers.In order to deteremine the community structure and its response to environmentfactors in different river sections from upstream to downstream, macroinvertebratecommunity and water quality were investigated in Dongjiang. The results were asfollows:(1) A total of117taxon (4phylum,8classes,20orders,54families,102genera)were collected in Dongjiang in2012which belong to three groups: annulata, aquaticinsects and mollusc. Of which18families18genera32species were mullusc,2families4genera were Hirudinea,2families2genera were Crustacea, and6orders32families79genera were aquatic insects.(2) The average biomass was63.75g/m~2, average density was3214ind/m~2.There was obvious difference among macroinvertebrate groups. The highest biomasswas mid and upstream, while the high density occurred in the downstream and estuarysections. This was because mollusk account for92.3%of total biomass in mid andupstream. Big body size and heavy shells made the high biomass. Oligochaetaaccount for90.8%of total density, small body size made high density.(3) Correlation analysis was conducted between bioindex and physicochemicalfactors. The results indicated that DO, transparency, velocity, conductivity were the main environmental factors influenced the community structure of macroinvertebrate.There was a positive correlation between BI, Shannon-Wiener diversity index andtransparency respectively. This indicated that the biodiversity of macroinvertebratewas higher in clean water with high DO and transparency. Lower biodiversityoccurred in water with high velocity and conductivity.(4) The ecosystem health of Dongjiang was evaluated using BI andShannon-Wiener diversity index. The results indicated that the source region wasclean, water quality become poor as the human disturbance increased.19clean siteswere centered to upstream in the BI evalutaiton. Moderate and heavy polluted siteswere centered to downstream which account for36%and25%of the total sitesrespectively, no clean site was found in downstream. Severely polluted sites werefound near to estuary which account for5%.