[Functional Group Characteristics of Planktonic Diatoms and Their Relationship with Environmental Factors in the Ruxi River].

To elucidate the functional group characteristics of planktonic diatoms and their relationship with environment factors in the Ruxi River, multivariate statistical analysis and functional group classification were conducted in this study. The success pattern of a diatom functional group and its driving factor were analyzed for the Ruxi River, a typical tributary of Three Gorges Reservoir, after the phytoplankton community and environmental variables were investigated at three different stages: level water period (April 2014), dry season (December 2014), and wet season (July 2014), based on the characteristic of water level. The results showed that there were 10 diatom functional groups in the Ruxi River: the A, B, C, D, L, MP, P, T, X3, and S1 groups, and among them, MP was the most groups, but the dominant group was D group. Stepwise multiple regression analysis indicated that (TN) in the water column was the primary factor significantly affecting the densities in the normal water period, whereas turbidity, alkalinity, and pH significantly influenced the functional group densities in the normal water period. In the high water period, however, transparency was the most important environmental factor affecting the functional group densities. Additionally, the results of RDA analysis found that water temperature, electrical conductivity (Spc), oxidation-reduction potential (ORP), (DO), and (NO-N) were the main environmental factors that influenced the diversity of diatom functional groups in the Ruxi River. These results suggested that functional groups could well reflect the habitat characteristics of the Ruxi River and the effect of the nutrient element, nitrogen, to the success of phytoplankton functional groups and changes of water quality in the Ruxi River should be paid more attention.