拉萨河中下游底栖动物群落结构特征分析

Zoobenthos Community Structure in the Middle and Lower Reaches of Lhasa River

2013年10月,在拉萨河热震藏布-河口中下游河段及支流共设置16个采样断面（拉萨河干流10个、支流4个,雅鲁藏布江汇口2个）,对底栖动物进行了调查。样品分析结果表明：拉萨河评价河段干、支流底栖动物共31种,其中环节动物5种,占16.13%;软体动物3种,占9.68%;节肢动物23种,占74.19%。优势种有正颤蚓（Lumbricus tubifex）、四节蜉（Baetidae sp）、多足摇蚊（Polypedilum sp）、隐摇蚊（Cryptochironomus sp）、网石蝇（Perlodidae sp）、钩虾（Gammaridae sp）等。直孔电站影响河段底栖动物现存量较高,密度、生物量平均分别为31 911个/m2、117.65 g/m2。剔除直孔电站影响河段,拉萨河干流底栖动物密度、生物量分别为32个/m2、0.92 g/m2,支流密度、生物量分别为63个/m2、0.78 g/m2。底栖动物Shannon-Wiener指数为0-2.02。直孔电站运行对拉萨河中、下游河段底栖动物整体影响较小;对库区河段底栖动物群落结构影响较大,群落结构由流水型向耐氧、静水型的环节动物、摇蚊转化。

Zhikong power station, a large power station located in the middle reaches of Lhasa River, began operat- ing in September, 2007. Since construction was completed and operation began, zoobenthos community succession in the reservoir area has not been reported, even though it has c dance. This study characterizes the zoobenthos community in the hanged the aquatic ecosystem and bait fish abun- reservoir and the middle and lower reaches of the Lhasa River. Results will provide insight for predicting zoobenthos community dynamics on the plateau reservoir, managing the conflicting interests between development and water resource protection in Tibet and support habitat conservation in the river basin. A one month investigation on the zoobenthos was conducted at 16 sampling sites in the middle and lower reaches of Lhasa River and its tributaries （from Rezhenzangbu to the estuary） in October 2013, 10 sites in the main stem of Lhasa River, 4 in the tributaries and 2 in the estuaries of the Yarlung Zangbo River. Quantitative zoobenthos samples for Zhikong reservoir area were collected with a Peterson bottom sampler （1/16 m2）. Four to five mud samples were obtained at each site and mud samples were screened and rinsed with a 40 mesh screen. Qualitative zoobenthos samples were collected with a kick-net. Quantitative and qualitative sam- ples for other sites were collected with kick-net and brail dip net. The obtained arthropods and mollusks were fixed with 75% alcohol and the annelids were fixed with 5% formalin and all samples were then preserved with 70% al- cohol for an identification sequence, counting and weighing in the laboratory. A total of 31 species of zoobenthos were observed in the stem and tributaries of the Lhasa River, including 5 annelid species （ 16.13% ）, 3 mollusk species （9.68%） and 23 arthropod species （74.19%）. The dominant species were Baetidae sp. , Polypedilum sp. , Cryptochironomus sp. , Perlodidae sp. , Gammaridae sp. and Lumbricus Tubifex. The standing stock of zoob- enthos in Zhikong reservoir area was high, with the average zoobenthos density of 31 911 ind/m2 and biomass of 117.65 g/m2. While the average density and biomass of zoobenthos in the stem and the tributaries were 32 ind/m2, 0.92 g/m2 and 63 ind/m2, 0.78 g/m2, respectively, excluding the zoobenthos community in Zhikong reservoir area. The Shannon - Wiener index for the zoobenthos community ranged from 0 - 2.02. In general, the operation of Zhikong power station has little effect on the community structure of zoobenthos in the middle and lower reaches of the Lhasa River, but a large impact in Zhikong reservoir. The number of species, zoobenthos density and biomass increased significantly in Zhikong reservoir after the Zhikong power station began operating and the zoob- enthos species composition has succeeded from lotic species to oxytolerant and lentic species