Determination of water quality of Köprüçay River (Antalya) according to physicochemical parameters and epilithic diatoms

In this study, it was aimed to determine the water quality and diatom flora of the Köprüçay River, which is of great importance in terms of human use in many areas, according to epilithic diatoms and physicochemical parameters. A total of 10 stations were selected on the river during seasonal field studies. Ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), sulfate (SO4-2), bicarbonate (HCO3-), orthophosphate (PO4-P), chloride (Cl-), biochemical oxygen demand (BOD5), temperature (˚C), dissolved oxygen (mg/l), pH and electrical conductivity were measured and water quality classes were identified on the basis of the Surface Water Quality Regulations. Furthermore, physicochemical parameter data were compared with the water quality standard values for human consumption and drinking water use found in WHO, EPA, EU, and TS 266. For determining water quality classes based on epilithic diatoms, GDI (Rumeau and Coste, 1988), TDI (Kelly and Whitton, 1995), SI (Rott et al., 1997), TI (Schmedtje et al., 1998), TDI (Coring et al., 1999), and DI-CH (Buwal, 2002) indices were utilized. The highest values for electrical conductivity, sulfate, and chloride were determined at Station 10. The highest values for biochemical oxygen demand at all stations were observed during the winter season. Ammonium nitrogen and orthophosphate values were found below the analysis limit in all samplings. According to the Surface Water Quality Regulations, the average values of all stations were in the I. or II. quality class, only station 6 was in the III. quality class according to the dissolved oxygen value. At the same time, all average parameter values are within the standard value range found in WHO, EPA, EU, and TS 266. Calculations according to the Water Quality Index (WQI) were made in two different ways, based on the season and the station. As a result of all calculations, the data obtained was determined to be less than 50, meaning "perfect water". In this study, 117 taxa belonging to 51 genera of epilithic diatoms were identified. The genus with the highest number of species was Nitzschia with 11 species. Following Nitzschia, Gomphonema (with 10 species), Navicula (with 9 species) and Cymbella (with 7 species) were the next genera in order of abundance. Additionally, the most dominant taxon was Achnanthidium minutissimum (Kützing) Czarnecki. The quality class of all stations generally ranged between Class I. and Class II. based on epilithic diatoms. Sørensen similarity and Margalef diversity analyses were conducted to demonstrate the similarity or difference of the identified taxa among stations. Considering all the data obtained, it has been determined that there is low or moderate pollution at the stations in the Köprüçay River due to various reasons.