Figure 2 Gene presence and concentration across the different sampling sites (WWTPs) in the Danube River Basin. Shown are relative gene copy numbers (normalized to 16S rRNA). Fig. 1. Composition of chemicals in the effluent wastewater samples collected in the Danube River Basin. Pie plots for each sampling station (marked in red) represent the percentage (%) of each class of target compounds, whereas size of the pie plots is proportional to the cumulative concentration of all detected target compounds. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)