USE OF BENTHIC DIATOM COMMUNITIES TO EVALUATE WATER-QUALITY IN RIVERSOF SOUTHERN POLAND

Biological and chemical data were processed to estimate trophic stage and degree of pollution in several streams and rivers in southern Pola nd. The majority were eutrophic and some of them heavily polluted; onl y a few were oligo-mesotrophic. The differences in the water quality o f the rivers were reflected by different types of diatom community and also by the values for some diatom indices, which were calculated usi ng the latest version of the 'Omnidia' database software. Except for t he Sladecek's index, all diatom indices correlated significantly with organic load (COD), oxygen concentration, conductivity and most of the measured ions. Some indices showed a significant negative correlation with trophic level (expressed by NH4-N and PO4-P). In general, IPS (S pecific Pollution Sensitivity Index) and GDI (Generic Diatom Index) in dices gave the best results. Among the investigated diatom communities , only a few taxa indicated oligo-mesotrophy and oligo-beta-mesosaprob ity. Most of the sites were characterised by a greater relative contri bution of eutraphent and tolerant ones as well as alpha-mesosaprobic a nd polysaprobic diatoms. This study suggests that the structure of ben thic diatom communities and diatom indices, especially GDI, can be app lied for monitoring rivers in Poland.