Macrophytes of the River Danube: a diversity study of the Austrian stretch

The comprehensive survey of the aquatic macrophyte vegetation in the Austrian stretch of the Danube is part of a full inventory of the whole river from its source to its mouth. The strategic framework rests on tree pillars, a standard methodological approach, involvement of local working groups in each country along the river, and a Data Acquisition and Processing Centre located in Vienna (DAPC-V). Following this scheme working groups from seven countries in the Danube catchment area have agreed to collect and contribute relevant data, so far. The data base will be open to all contributors. Results from the Austrian stretch let us reconstruct the important changes in aquatic vegetation caused by the regulation measures in the late 19(th) century and by the construction of hydro-electric power plants between 1950 and 1997. The results of this survey enhance: our knowledge on macrophyte diversity, flow preference, the impact of hydro-electric power plants, and historical conditions. Practical use of the future data base will be made for environmental diversity and succession studies, planning of conservation and restoration measures, and by describing reference sites with respect to ecological water quality assessments. Aquatic macrophytes could be the first group of organisms for which a geo-referenced information base is available for the whole length of the second largest river of Europe, the Danube.