The Pearson correlation results of the environmental factors revealed that many environmental factors are closely related. Table 2 reflected that the WT was highly positively correlated to Wid, Vel, Cond, NO3--N, and pH value and negatively associated with DO and NH4+-N. Vel was significantly positively correlated to CODMn and negatively associated with NH4+-N. Cond and NO3--N presented significant positive correlations.
3.2 Macroinvertebrate communities and functional feeding groups
During the sampling, 116 species comprising 3 phylum, 6 classes, 14 families, and 96 genera were observed and classified into annelids (2.25%), mollusks (8.99%), and arthropods (88.76%). Species with relative abundance exceeding 2% were dominant ones(Yan et al., 2017), which changed significantly among different seasons (Table 3). A total of 34 dominant species were identified (20 in wet season, 28 in normal season, and 24 in dry season). Enochrus sp. and Elmomorphus brevicornis Sharp were the only common dominant species in wet season.Corbicula fluminea, Ephemerella sp., Brachythemis leucosticte,and Nehalennia speciosa were in normal season. Radix swinhoei and Micrasema sp. were in dry season.
Table3. Dominant macroinvertebrate species and their dominance index in each season