Abstract:

An investigation on periphyton and zoobenthos in the Xaitongmoin reach of the Yarlung Zangbo River was carried out in October and November,2008 and March and August,2009,respectively.Altogether 104 genera, 12 phyla of periphyton, 26 genera, 3 phyla of zoobenthos were collected in this study.The density and biomass of periphyton were highest in Spring,which were 1 478 501.6 ind./cm2 and 45 912.8×10-4 mg/cm2,respectively.The density and biomass of periphyton were lowest in Summer,which were 1 037.1 ind./cm2 and 457×10-4 mg/cm2,respectively.The density of zoobenthos were highest (7 706.2 ind./m2) in Autumn,and the biomass of zoobenthos were highest (128 g/m2) in Spring. Margalef’s richness index (D),ShannonWiener index (H’) and Pielou’s evenness index (J) of periphyton and zoobenthos were all highest in Summer.The most prevalent organisms within periphyton was diatoms,the principal genera were 〖WTBX〗Diatoma〖WTBZ〗 and Cymbella. The most prevalent organisms within zoobenthos was chironomid larvae.There were seasonal variations with the species and biomass of periphyton and zoobenthos in the Xaitongmoin reach of the Yarlung Zangbo River,which may be relative to the ecological factors such as water level.