3.6 Water quality and biodiversity assessment
To test whether Phylogenetic diversity (PD) can be used as a metrics of Index of Biotic Integrity (IBI), the PD of each sampling site was calculated through community data and the phylogenetic tree constructed using sequences of mitochondrial COI gene (Table S3). The box plot and t-test were used to compare the PD between the reference and disturbance sites (Fig. 5). The PD values of reference sites were significantly higher than those in disturbance sites (One-way ANOVA, p<0.05), and there is no overlap between reference and disturbance box in box plot.
Macroinvertebrate assemblages were utilized to calculate the biological and diversity index. The grades of assessment in the Irtysh river were as follows: B-IBI>2.04 represents excellent, 1.53< B-IBI>2.04 represents good, 1.02<B-IBI≤1.53 represents fair, 0.51<B-IBI≤1.02 represents poor, and B-IBI≤0.51 represents bad. For the Ili river, the grades were as follows: B-IBI>1.31 represents excellent, 1.01<B-IBI<1.31 represents good, 0.68<B-IBI<1.01 represents fair, 0.34<B-IBI<0.68 represents poor, and B-IBI<0.34 represents bad. The water quality and biodiversity of each site in the studied rivers were evaluated in Table S4. In the Irtysh River, four of eight sites were excellent and only one site was poor. However, in the Ili River, two of eight sites were excellent and two sites were Bad.