Implementation of the European Water Framework Directive: Development of a system for water quality assessment of Hungarian running waters with diatoms

The purpose of the paper is (1) to make an inventory of the diatom assemblages of the Hungarian running water types; (2) to assess relationships between the species composition and environmental variables; (3) to adapt existing metrics to the Hungarian situation; and (4) to present a map of the of diatom inferred quality of the country's running waters. In spring 2005, diatom samples were taken in 339 streams. Samples for analysis of water chemistry were taken at most of the stations. The diatom species composition was investigated using standard methods and 496 taxa were found. Ordination by detrended correspondence analysis (DCA) revealed that current velocity, altitude, shading, oxygen and alkalinity are master variables for the species composition of diatoms. Nutrients are of less importance in determining the diatom distribution over the whole country, but regionally they can have a considerable impact. Twelve diatom river types (IndVal method) were distinguished. The existing physiographic river typology is too detailed for diatom assemblages. Human impact has caused shifts in the assemblages. For the estimation of water quality in the running waters, the IPS (Index of Pollution Sensitivity) was calculated and the class boundary limits were adapted to the Hungarian geomorphology. Different class boundaries are set for high-, mid- and low-altitude streams. Using these boundaries, 81 % of the streams have a high or good quality. Poor or bad conditions of the streams are often due to domestic sewage load, but industrial pollution may also be important. Provisionally, reference sites are selected.