Studies On The Spatial-temporal Variation And Biological Integrity Of Macroinvertebrate In The Xiangxi River, And The Impact Of Small Hydro Power On Its Communities

Based on the long-term sampling of macroinvertebrate communities in the Xiangxi River system, several researches were carried out: 1) the spatial-temporal patterns of the macroinvertebrate communities in the Xiangxi River, and their relationships with environmental factors. 2) The efficiency was compared with three different methods in sampling the macroinvertebrate communities, including the stone-picking method, the D-frame hand net and the Surber net. 3) Based on the benthic index of the biological integrity (B-IBI), the the Xiangxi River system health was evaluated. 4) The effect of the small hydro power station on the macroinvertebrate communities and the river ecosystem health was analyzed. 5) The macroinvertebrate communities of three different streams were compared. The three streams had similar latitude, river length and watershed area. All were the tributaries of the Yangtse River and located in the upstream areas. The main results are as follows:1. The stream of Xiangxi River system was divided into six orders based on 1:50,000 relief maps. A total of fifty-three samplings sites were sampled. Baetis spp (Ephemeroptera), Epeorus sp. (Ephemeroptera), Antocha sp. (Diptera) and Glossosoma sp. (Trichoptera) were the main taxa and relative abundance respectively were 19.46%, 10.59%, 9.22% and 8.45% in the Xiangxi River. The macroinvertebrates communities were divided five main functional feeding groups, including predators (PR), shredders (SH), scrapers (SC), collector-gatherers (GC) and collector-filterers (FC). The collector-gatherers and scrapers, who feed on benthic algae, riparian detritus and fine particulate organic matter from the stream bottom, were the main groups in the Xiangxi River system. The density and biomass of different functional feeding groups changed in the different stream orders. The GC and FC increased with the increase of stream order, while the SH and SC decreased. The PR density was higher in the downstream and biomass was higher in the upstream. Two-way indictor species analysis and detrended correspondence analysis...