Trophic conditions in rivers and streams – significance for biological quality elements of the European Water Framework Directive

In the past, saprobic and trophic conditions were both used as indicators to assess and monitor the quality of surface water bodies. Now, with the introduction of the European Water Framework Directive (WFD), the focus in the assessment of aquatic systems has shifted towards better integration of biocoenotic parameters, expressed as biological quality elements. With this change, saprobity is still used, at least as partially, in the evaluation of benthic invertebrate fauna. The term ‘trophic status’, however, no longer appears as a separate criterion. It is the aim of this paper to show that all quality components depend to a greater or lesser extent on the water bodies' trophic status, so that this term will maintain its significance as a key influencing factor.