A comparison of various indices based on benthic macrofauna for the assessment of the ecological status of selected Carpathian streams

The biological indices MMI-PL, BMWP-PL, and %EPT were applied to compare the ecological status of Carpathian flysch stream sectors situated above and below sewage treatment plants. MMI-PL was found to be the most sensitive, whereas BMWP-PL indicated a very good ecological status at all sampling stations despite an increased trophic level of water in polluted sectors. %EPT proved to be an unreliable index because of its strong fluctuations resulting mainly from unstable densities of benthic invertebrate groups not included therein. The analyses of coli titers and water chemistry in the same stream sectors revealed temporary pollution at both types of stations.