[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.

[Influence of cascaded exploitation of small hydropower on phytoplankton in Xiangxi River].

With the five small hydropowers (SHPs) from up- to downstream of Xiangxi River as test objects, this paper studied the influence of SHPs cascaded exploitation on the phytoplankton in the river. The results showed that phytoplankton assemblages were dominated by diatoms, occupying 95.54% of the total number of species. Achnanthes linearis, A. lanceolata var. elliptica and Cocconeis placentula were the most abundant species, with the relative abundance being 23.96%, 18.62% and 12.48%, respectively. The average algal density at 25 sampling sites was 6.29 x 10(5) ind x L(-1), with the maximum of 1.81 x 10(6) ind x L(-1) and the minimum of 2.35 x 10(5) ind x L(-1). Two-way ANOVA indicated that water flow velocity was the main factor affecting the phytoplankton. The establishment of the cascaded SHPs on the river made the habitat of lower reach has a significant difference with the others, resulting in a dramatic change of many parameters including Margalef diversity index, species richness, generic richness, taxonomic composition, and the percentage of diatoms.