西藏雅鲁藏布江雄村河段及其支流底栖动物初步研究

PRELIMINARY STUDY ON MACROZOOBENTHOS IN YARLUNG ZANGBO RIVER AND ITS BRANCHES AROUND XIONGCUN,TIBET,CHINA

2007年6月对西藏雅鲁藏布江雄村河段及其支流底栖动物进行了调查。共采集到底栖动物47种,隶属于20科42属,其中水生昆虫种类最多(92.8%)。干、支流底栖动物种类组成差异较大,且支流物种多样性高于干流。干流底栖动物现存量明显小于支流,干流密度和生物量(干重)均值分别为38.5±9.8 ind/m2和0.010±0.003g/m2,支流均值分别为130.2±15.0 ind/m2和0.055±0.040 g/m2。干流优势种为3种摇蚊科幼虫和1种腹足类;支流优势种为3种蜉蝣目稚虫和1种摇蚊科幼虫。在功能摄食类群方面,干流以直接收集者和刮食者为主,支流以直接收集者和捕食者为主。分析表明,干、支流底栖动物群落结构的差异主要与底质类型有关。比较发现,雅鲁藏布江与喜马拉雅山南坡河流底栖动物群落结构的差异较大;高海拔地区底栖动物现存量明显低于低海拔地区河流。

Investigation of macrozoobenthos in the mainstream and branches of the Yarlung Zangbo River near Xiongcun,Tibet,was carried out in June 2007.Altogether 47 species belonging to 20 families and 42 genera were recorded,with the dominant group being aquatic insects（92.8%）.Species composition of macrozoobenthos had great differences between the mainstream and its branches.Species diversity of the mainstream was lower than those of the branches.The standing crop of macrozoobenthos was much lower in the mainstream than those in the branches.The mean density and biomass（dry weight） of macrozoobenthos were 38.5±9.8 ind/m2,0.010±0.003 g/m2 in the mainstream and 130.2±15.0 ind/m2,0.055±0.040 g/m2 in branches,respectively.Three chironomids and one gastropod dominated the benthic community in the mainstream,while three mayflies and one chironomid did in the branches.In terms of functional feeding groups,collector-gatherers and scrapers dominated the mainstream community,while collector-gatherers and predators did in the branches.Analysis showed that differences of macrozoobenthos community between the mainstream and its branches were mainly due to the difference of sediment types.Comparison with other studies suggested that macrozoobenthos community in Yarlung Zangbo River was quite different from those of rivers in the south Himalayas.Also,the standing crops of riverine macrobenthos at high altitudes were much lower than those of the Yangtze lowlands.