Does the ecoregion approach support the typological demands of the EU 'Water Framework Directive'?

The new European assessment system for freshwater ecosystems is based on reference conditions. As the ecological status of rivers must be determined with respect to the near-natural reference conditions focus is given to establish a typological framework. A basic part of this typology is the ecoregion approach. Multivariate analysis of the benthic invertebrate assemblages confirmed the grouping of Austrian fluvial landscapes into four of the European aquatic ecoregions: Alps, Central Highlands, Hungarian Lowlands and the Dinaric Western Balkan. The benthic assemblages are more homogeneous within an ecoregion than among different ecoregions. Analyzing sites from adjacent areas in Italy, Germany and the Czech Republic clearly indicated that the ecoregion concept fulfils the goal of independence from political borders and that this concept can be used in Europe for implementing the Water Framework Directive. Nevertheless, considering the detailed structure of central European landscapes, the ecoregions are too large and variable to provide a framework for regional management based on ecological data. With respect to the variety of the central European river faunas a further division into bioregions was seen as necessary. Combining a priori derived types of Austrian riverine-landscape-types and major surface-water-types with the results of the multivariate analysis (groups of similar benthic assemblages) led to a description of 15 'Austrian Fluvial Bioregions'. Fluvial Bioregions are very strong descriptors of the faunal assemblages; their determinative character is stronger than the ecological quality of a site. Within the bioregions, the natural variability of several biological measures metrics, indexes) is low. Consequently, the discriminatory power of the measures for evaluating ecological status is increased by using the bioregional classification.