[Community structure of phycophyta and evaluation of water quality in Sichuan section of Jialing River].

In order to understand the characteristics of the phycophyta community structure and water quality in Sichuan section of Jialing River, water samples were collected from 12 sites along the section in dry season (January) and rainy season (September), with the phycophyta species composition, Shannon diversity index (H'), Pielou evenness index (E), and Margalef richness index (d) analyzed. A total of 171 phycophyta species (including variety) were collected, belonging to 8 phyla, 42 families, and 95 genera, among which, Bacillariophyta, Chlorophyta, and Cyanophyta were the dominant groups. In dry season, the mean cell density of the phycophyta was 14.71 x 10(4) ind x L(-1), being the highest at sites JX (28.33.4 x 10(4) ind x L(-1)) and HYZ (25.40 x 10(4) ind x L(-1)), and diatom species had a higher richness than the others. In rainy season, the mean cell density was only 10.78 x 10(4) ind x L(-1), being the lowest (3.31 x 10(4) ind x L(-1)) at site QJ, and the species richness of chlorophyta and cyanobateria had somewhat increase. In the whole section, the mean d, H', and E of the phycophyta were 2.35, 1.60, and 0.31 in dry season, and 2.57, 2.09, and 0.39 in rainy season, respectively. Our results indicated that there were significant differences in the spatiotemporal distribution patterns of the community structure, cell density, diversity index, and evenness index of phycophyta in Sichuan section of Jialing River. The water quality of this section was overall belonged to mesosaprobic, being better at sites JX and SX (belonged to oligosaprobic or beta-mesosaprobic), but worse at sites CX, HYZ, XZ, and QJ (belonged to alpha-mesosaprobic).