Use of epilithic diatoms to evaluate water quality in the Karasu River of Turkey.

Epilithic diatom assemblages were used to evaluate water quality in the Karasu River basin (Turkey), which was polluted by industrial, agricultural and urban wastes. A total of 73 diatom taxa belonging to 22 genera were found from all seven sampling stations located in the Rivet basin. The most pollution tolerant species Gomphonema parvulum, Nitzchia palea, Navicida cryptocephala were found in high densities at the polluted stations. Organic load (COD), biological oxygen demand in 5 days (BOD5) and concentrations of nutrients (NO3--N, NO2--N; NH4+-N and PO43--P) were correlated negatively with dissolved oxygen. Except for generic index of diatoms (67), all diatom indices were correlated significantly with COD, BOD5, dissolved oxygen and concentrations of nutrients. Saprobity index (SI), trophic diatom index (TDI) and the percentage pollution tolerant valves values suggested that the stations 111, IV located in the River basin were eutrophicated and organically polluted.