Conceptual study - An improved method to assess acidification in German streams by using benthic macroinvertebrates

The present study is based mainly upon the authors' hydrochemical and hydrobiological studies of small silicate streams in South-West Germany, principally in the Black Forest and the Odenwald. The aim of the paper is the adaptation of a practically proven four-level biological classification system of different degrees of acidity using benthic maroinvertebrates to a five-level system of acidification of mainly upland streams with low buffer capacity. The main reason for such a five-class system is the Water Framework Directive of the European Union (EU WFD), which lays down a five-level classification system for the assessment of the ecological quality of waters. The biological method of assessing the state of acidity for evaluation of the degree of anthropogenic acidification under the directive, and principles of the EU WFD, are also described. A list of 278 taxa of the macrozoobenthos has been reclassified from a four-level system to a five-level biological indication system, based upon the authors' scientific expertise and the latest references from literature of different acid sensitive areas in Germany.