Yiming, H; Baozhu, P; Xiaoming, J; Wanxiang, J; Penghui, Z; Lei, Z; Haiqiang, Y
The upper reaches of the Hanjiang River are the source-water area of the Danjiangkou Reservoir. Its ecological status plays an important role in ensuring the ecological security of the Hanjiang River Basin and the South-to-North Water Transfer Project. In November 2017 and April 2018, we conducted a systematic survey in the upper reaches of the Hanjiang River and its five typical tributaries, in order to find out the characteristics of benthic macroinvertebrate communities in the upper reaches of the Hanjiang River and the typical tributaries of the southern slope of the Qinling Mountains, and to evaluate their bioassessment of water quality. Altogether 240 species of macroinvertebrates were collected, including 209 species of aquatic insects, 13 species of mollusks, 9 species of annelids and 9 species of other groups. Among them, Baetis sp. was the dominant species in all rivers. In addition, other species included Paraleptophlebia sp., Caenis sp., Heptagenia sp., Baetiella sp., Orthocladius sp., Hydropsyche sp., Ephemera sp., Cincticostella sp., Epeorus sp., Sympotthastia sp. and Eukiefferiella sp. From the density of various groups, aquatic insects had an absolute advantage in the Hanjiang River and its five tributaries, accounting for 90.8%-98.9% of the total density. In terms of biomass, in addition to the absolute advantage of mollusks in the main stream of the Hanjiang River, aquatic insects had an absolute advantage in each tributary, accounting for 47.0%-98.9% of the total biomass. In terms of the density of functional feeding groups, direct collectors were the main functional feeding groups in the Hanjiang River and its tributaries, while there were differences in terms of biomass. The predators were the main functional feeding groups in the Jinshui River and the Xun River. The scrapers were the main functional feeding group of the Hanjiang River and the Yue River. The collector-gatherers were the main functional feeding group in the Jinqian River. The collector-filterers were the main functional feeding group in the Xushui River. The redundancy analysis results showed that velocity, total phosphorus and conductivity were the key environmental factors affecting the distribution of benthic macroinvertebrate in the Hanjiang River and its tributaries. The bioassessment of water quality was carried out by using the biotic index (BI) and the Shannon-Wiener index. The evaluation results showed that a few stream sections of the Hanjiang River, the downstream of the Xushui River, the downstream of the Yue River and the mid-lower reaches of the Xun River were slightly to moderately polluted, the other stream sites were in a clean state. The research results can provide basis for ecological management and scientific protection in the upper reaches of the Hanjiang River.