Graphical representation of the two primary axes (Axis 2, ordinate; Axis 1, abscissa) of the principal-components analysis (PCA) demonstrating the ordination of the sampling sites with respect to the environmental variables. Key to abbreviations: S1, Site 1; S2, Site 2; S3, Site 3; B, benthos; E, Egeria densa; L, Ludwigia peploides; M, Senecio bonariensis; H, Hydrocotyle bonariensis; A, Alternanthera philoxeroides; T, Typha latifolia; and F, Mougeotia; 1014, October 2014; 0515, May 2015; 0815, August 2015. Physicochemical parameters: conductivity, Cond; turbidity, Turb; nitrates, NO₃⁻; nitrites, NO₂⁻; ammonium, NH₄⁺; phosphates, PO₄⁻³; dissolved-oxygen concentration, DO; chemical-oxygen demand, COD; biochemical-oxygen demand, BOD; and organic matter in the sediments, OM. The areas demarcated by the broken red lines indicate the same sampling site.