The distribution of benthic invertebrates along the Austrian stretch of the River Danube and its relevance as an indicator of zoogeographical and water quality patterns - part 1.

Abstract

A total of 1289 invertebrate species is now known along the Austrian stretch of the River Danube. These species characterize the free-flowing section of the river as a transition zone of the hyporhithron/epipotamon. Most species of the Austrian Danube have individual saprobic values between 1.6 and 2.8 on average characterizing a beta-mesosaprobic zone. When different family-based indices and scores were converted into saprobic water quality classes, samples with the same data-base (set of species and their absolute abundance) differed between classes I and III. These deviations from the proven water quality class II can be explained 1. by different environmental conditions, such as the relationship between species abundance and hydrological variables rather than from real differences in water quality, 2. from calculations on higher taxonomic levels. In principal, the deviations of ASPT estimates from the real saprobic water quality situation in Austrian rivers are of little use in making management decisions.