8 - Diversity, connectivity and variability of littoral, surface water ecotones in three side arms of the Szigetköz region (Danube, Hungary)

Summary

ABSTRACT The 137 km long Szigetköz side-arm system extends on the right side of the river Danube in Hungary and shows the unique characteristics of river, shore, riparian forest, and groundwater ecotones. The investigated three side arms are in different alluvial stages, their surface sediment is variable: sand, sandy mud, mud, mud covered with detritus. The composition, life forms, and cover of aquatic macrophyte stands are good describers of the different side arms. On the surface of the sediment, the habitats are numerous and varied, and linked to the vegetation and open water region. Crustacean communities of these habitats are very diverse, mosaic-form, and are in dynamic connection with each other mainly through the developing stages, and even through certain stenoecious species.

INTRODUCTION

The Szigetköz Danube stretch in Hungary (1848–1806 river km) flows on its own alluvial cone. Fall is small, 3–10 cm km⁻¹. A 137 km long side-arm system extends on the right side of the river, with 22.2 million m³ volume. The whole region is composed of five side-arm systems. Regulation activities began in the last century. The main goal of the engineering has been the assurance of the shipping on the Danube and the flood control. The present situation is the result of the regulation works carried out in 1966–1983 when numbers and heights of closing dams were increased. During low and mean water periods, 90 % of the water discharge flows in the Danube itself. Therefore, quantity and intensity of water supply of the side arms have decreased. The situation of the water table in the Szigetkoz region did not changed drastically in this period.