Biplot of the analysis of redundancy (RDA) showing the ordination of the taxa with respect to the environmental variables measured at the study sites. In the figure, Axis 2 is the ordinate and Axis 1 the abscissa. For the abbreviations of the taxa, cf. Table 1. For the purpose of clarity, the figure includes only those taxa that were present at a frequency of 5% or greater. Key to abbreviations for the physicochemical parameters: conductivity, Cond.; turbidity, Tur.; nitrates, NO₃⁻; phosphates, PO₄⁻³; dissolved-oxygen concentration, DO; biochemical-oxygen demand, BOD.