Figure 4

Changes in the relative abundance of bacteria at the phylum level along the pollution gradient of the Białka river. Three sampling seasons, i.e. summer, winter, and spring are shown from left to right. Arrow graph shows the expected bacterial pollution gradient, darker brown shade indicates the more contaminated sites, the arrowhead indicates the course of Białka river. Site abbreviations are as follows: GW—groundwater; TNP—Tatra National Park; USTP—upstream of the sewage treatment plant; STP—sewage treatment plant; DSTP1—c.a. 3 km downstream of the STP; DSTP2—c.a. 7 km downstream of the STP (for detailed description, please see caption of Fig. 2).