We used seven biotic indices to determine the water quality of Karabal Stream (Gediz River) in West Anatolia, Turkey. The indices were based on benthic macroinvertebrate and physicochemical parameters: Saprobi Index (SI), Biological Monitoring Working Party (BMWP), Average Score per Taxon (ASPT), Family Biotic Index (FBI), Belgian Biotic Index (BBI), EPT-Taxa [%] were used as biotic indices and Shannon-Weaver index (SWDI), Simpsons index (SDI) and Margalef index (MDI) for diversity. Ten taxonomic groups were found in Karabal Stream consisting of Crustacea, Oligochaeta, Gastrapoda, Ephemeroptera, Plecoptera, Trichoptera, Odonata, Coleoptera, Diptera, and Hemiptera. The water quality along the stream varied from good class in the upstream stations, to moderate in downstream stations according to the most suitable indices. According to canonic correspondence analysis (CCA), the distributions of Diptera, Oligochaeta, and Hemiptera species are positively correlated to EC, Cl, Turbidity, Temperature, NH4-N, NO2-N, and NO3-N while they are negatively correlated to DO, DOS and pH. The distributions of EPT species are positively correlated to DO, DOS and pH. According to Pearson’s correlation, the BBI, BMWP (Original), BMWP (Spanish), and EPT-Taxa [%] metrics were sufficient in the estimation of water quality in the examined watercourse. Considering studies in surface waters of Turkey, the BMWP and EPT-Taxa [%] indices reflect the water quality as correctly in all studies we examined, however, BBI did not always show reliable results. Therefore there is a need for the establishment of a Turkish Biotic Index which takes into account country-specific macroinvertebrates, their abundance, biology, and ecology.
