Factors Influencing the Chemical Characteristics and Nutrient Retention / Release Potential of Wetlands in the Middle (Hungarian) and Lower (Bulgarian) Danube River

Several physical and chemical variables including nutrients (N- and P- forms) of wetlands in the Middle and Lower Danube River, each presented by five water bodies, were measured and analysed. The applica - tion of multivariate redundancy analysis (RDA) showed that variables reflecting the degree of wetland connectivity (isolation) to the main river and the macrophyte development are among the main and com- mon factors explaining spatial variations of recorded variables, nutrient concentration ratios between wetlands and the river and ordination of wetland sampling sites. The morphological type of wetlands related to their connectivity to the river seems to influence the nutrient dynamics (i.e. release/ retention) stronger in the Lower Danube River, while factors such as flow availability and direction are of significant importance in the wetlands of the Middle Danube River.