Spatial distribution of macroinvertebrates in Xiangxi River.

An investigation was made from July 2005 to June 2006 to understand the spatial distribution of macroinvertebrates in Xiangxi River, the largest tributary in Hubei portion of Three Gorges Reservoir. The results showed that Ephemeroptera baetis spp., Ephemeroptera epeorus spp., and Plecoptera nemoura spp. were the dominant taxa. There existed greater differences in the habitat characters and in the community structure of macroinvertebrates among the major tributaries of Xiangxi River, and the relative abundance of functional feeding groups could reflect the characters of different habitats. A comparison of the diversity of dominant taxa and their tolerance towards pollution among the major tributaries showed that Jiuchong River had the best habitat, followed by the main stream of Xiangxi River, and Gaolan River and Gufu River. Canonical correspondence analysis showed that the NH₄⁺-N concentration in the main stream of Xiangxi River, the pH, turbidity, water depth, SiO₂, conductance, and alkalinity in Jiuchong River, the turbidity in Gaolan River, and the NH₄⁺-N and NO₃^--N concentrations in Gufu River had significant impact on the community structure of macroinvertebrates. [ABSTRACT FROM AUTHOR]