F1×F2 plane of the Canonical correspondence analysis (CCA) based on 21 mayfly taxa and 14 environmental variables. For the abbreviations of the taxa codes (blue triangle symbols) see Table 2. Legend: Environmental variables (red arrow symbols): Tw – water temperature (°C), Oxy – dissolved oxygen content (mg/L), Con – conductivity (μS/cm), pH – pH, NH4+ – ammonium (mgN/L), NO3- – nitrates (mgN/L), TN – total nitrogen (mgN/L), PO4 3− – orthophosphates (mgP/L), TOC – total organic carbon (mg/L), BOD5 – biological oxygen demand (mgO2/L), CODMn – chemical oxygen demand (mgO2/L), vegetation – aquatic vegetation/phytal, fine sediment – silt, mud and sand, lithal – stones and gravel.