FIGURE 3.

Taxonomic classification of 16S rRNA amplicons. (A) Hierarchical clustering of samples based on the presence/absence OTUs for City#1 (brown labels) and City#2 (blue labels) sampling sites. A gradient from dark to light colors reflects chlorine concentration at each site. (B) Non-metric multidimensional scaling plot of the sample based on the presence/absence and the quantification of reads classified in bacterial OTUs (Ward distance), displayed with the same color-code as in (A). (C) Bacterial composition at the phylum level, showing the large predominance of Proteobacteria, and some Bacteroidetes, Cyanobacteria, and Chlamydiales in a few samples. (D) Bacterial composition at the species level, showing the large predominance of Pseudomonas spp. in the samples with higher chlorine, and the abundance of unknown proteobacterial clades as well as Sphingomonales in samples with lower chlorine concentration. Only identified species encompassing more than 1% of reads were represented in (D).