Changes of macrobenthos community and their relationships with environmental factors along cascading reservoirs of Xiangxi River Basin,China

An investigation was made on the macrobenthos communities in three cascading reservoirs in Xiangxi River Basin in October,2005 and 2011,respectively,aimed to explore the changes of the macrobenthos communities and their relationships with the environment. As compared with that in 2005,the macrobenthos community in the three reservoirs in 2011 changed to some extent. In Gudongkou Reservoir I,Oligochaeta was still dominant,and the total macrob- enthos density increased. In Gudongkou Reservoir Ⅱ,the dominance degree of Chironomidae descended,while the total macrobenthos density ascended. Meanwhile,the relative abundance of Procladius sp. declined dramatically from 94. 5% to 35. 5% ,while that of Limnodrilus hoffmeisteri increased to 36% . The macrobenthos community in Xiangxi Bay had great change. Since Chironomidae replaced Tubificidae as the absolutely preponderant species, the relative abundance of Chironomidae reached 89% ,but the total macrobenthos density decreased. These changes were attributed to the drastic water level fluctuation of the Three-Gorges Reservoir. The canonical correspondence analysis ( CCA) on the relationships between the macrobenthos community and environmental factors in the three reservoirs showed that Procladius sp. preferred the waters with higher turbidity,while Limnodrilus hoffmeisteri and Tubifex tubifex preferred the waterswith higher water column stability and lower bottom water temperature.