Abstract: We collected data of benthic macroinvertebrates and environmental factors of the Lake Taihu basin from 73 sampling sites, aiming to explore the functional characteristics of river ecosystem based on the parameters of functional feeding groups. The relationships between biodiversity indices and parameters of functional feeding groups in two ecological regions were analyzed. The results showed that biodiversity indices of the western hilly area were generally higher than those of the eastern plain area. The correlations between parameters of functional feeding groups and functional diversity indices were higher than other biodiversity indices. Specially, material circulation was negatively correlated with functional evenness index and species diversity indices, while material longitudinal transport was positively correlated with functional richness index and Rao Q index. There was also a positive correlation between coastal material input and species diversity indices. Results of redundancy analysis indicated that dissolved oxygen, total nitrogen concentration, nitrate nitrogen concentration, substrate index, and turbidity were the environmental factors with significant influences on biodiversity indices, while dissolved oxygen and nitrate nitrogen concentration greatly influenced the parameters of functional feeding groups. According to the piecewise structural equation models, nutrient concentrations had negative effect on ecosystem function directly or indirectly through altering biodiversity indices. Substrate index would have a positive effect on ecosystem function directly, and a positive effect through the biodiversity indices indirectly.

Key words: functional diversity, taxonomic diversity, functional feeding group, redundancy analysis, piecewise structural equation model