Aquatic macrophytes as bioindicators of water chemistry in nutrient rich backwaters along the Upper-Tisza river (in Hungary)

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We assessed the relationship of vegetation composition and water chemical parameters in fi ve nutrient rich backwaters in NE Hungary. We used 126 plots and water samples analysed for 19 water chemical parameters. Our hypothesis was that environmental variables might be decisive for macrophyte species composition in waters with different nutrient content. We also supposed that community-environment and species-environment relationship of nutrient rich water may differ from nutrient poor ones. TWINSPAN analysis was used to reveal the main vegetation units, and detrended canonical correspondence analysis (DCCA) was used to explore the water chemical demands of these communities and the species-water chemical parameters relationships. We found 8 communities by TWINSPAN. Among the water chemical parameters Ca 2+ , COD, NO2, Mg 2+ , Cl - were important in differentiating the communities. In the nutrient rich backwaters we found similar results as other authors found in nutrient poor waters and fens. Glycerietum maximae association found in waters with high amount of COD and NO2 - , Typhetum angustifoliae association correlated negatively with these water chemi- cal parameters and Sparganietum erecti and Potametum lucentis associations prefer both habitats. Bolbo- schoenion and Schoenoplectetum lacustris associations have been found to prefer waters with high amount of Cl - . Trapetum natantis and Ceratophyllo-Nymphaeetum albae associations found to prefer waters with low amount of Ca 2+ , COD, NO2 - , Mg 2+ and Cl - , which proved the vulnerability of these protected associations in nutrient rich waters. In the case of species-water chemical parameters relationship we found high nitrogen correla- tion of Ceratophyllum demersum and high Ca 2+ correlation of Potamogeton lucens.