Zum Stoffhaushalt der mittleren Donau
Various components of the oxygen regime in the middle stretch of the River Danube (676 km long) have been investigated through joint efforts from Slovakia, Hungary and Yugoslavia in the years 1979-1986. Phytoplankton photosynthesis is of major importance for the oxygen regime and for the cycling of organic matter. This factor is especially pronounced in that part of the river where it forms the border between Hungary and Slovakia. Water temperature, oxygen-concentration and -saturation as well as primary productivity and organic matter concentration increase between Rajka and Baja, the Hungarian part of the Danube, while these variables decrease near Belgrade. Long term analysis of the data indicate significant reduction of sediment load as a consequence of river-dams upstream. Algal concentration and primary production has increased as a result of better light availability. A tendency of increasing eutrophication has been observed.