Seasonal variation of hydrochemistry, algal biomass and phyto-plankton composition in a Danubian backwater system
Limberger, R.; Schagerl, Michael
Water chemistry, phytoplankton biomass and algal class distribution were studied for one year at an impounded part of the River Danube and at three water bodies of a backwater system upstream of Vienna. One backwater was frequently connected to the Danube and therefore contained similar amounts of nutrients and algal biomass. At this study site and in the Danube, phytoplankton was limited by physical factors (light and discharge) and dominated by fast-growing diatoms. The remaining water bodies received river water only at two flood pulses that led to a dilution of algal biomass and to an input of nutrients and suspended solids. With the beginning of isolation, the previously similar environmental conditions started to differ and biotic interactions became more important. In one of the water bodies, the phytoplankton biomass was held low by the poor nutrient supply and by zooplankton grazing. In the other water body, the high algal biomass and the frequent changes of the dominating algal groups could be attributed to its shallowness that resulted in elevated nutrient concentrations.