Water Quality Assessment by Means of Bio-Indication: A Case Study of Ergene River Using Biological Diatom Index

The Ergene River is the most significant fluvial ecosystem located in the Thrace Region of Turkey. But it is being exposed to an intensive organic - inorganic pollution by means of agricultural - industrial applications conducted around its basin. In this research, the epipelic (EPP) diatoms of the Ergene River were investigated and the water quality was evaluated using the determined physical, chemical and biological data. EPP diatom samples were collected from upstream, middlestream and downstream of the Ergene River and certain physicochemical parameters (dissolved oxygen, oxygen saturation, pH, electrical conductivity, total dissolved solids, salinity, turbidity, nitrate, nitrite, ammonium, phosphate, sulphate, fluoride, chemical oxygen demand, biological oxygen demand and oxidation-reduction potential) were measured during the field - laboratory studies. Also, the Biological Diatom Index (BDI) was used to determine the trophic status of the Ergene River in terms of EPP diatoms. According to the results of the physicochemical analysis, upstream of the Ergene River has Class I - II water quality and middle - downstream of the Ergene River have Class III - IV water quality in general. According to the results of the biological analysis, 24 diatom species were recorded in the upstream samples, 4 diatom species were recorded in the middlestream samples. and 7 diatom species were recorded in the downstream samples. Cymbopleura amphicephala (Nageli) Krammer, Nitzschia umbonata (Ehrenberg) Lange-Bertalot and Nitzschia capitellata Hustedt were determined as the most dominant species in the up - middle - downstream of Ergene River respectively. According to the result of the BDI, the upstream of Ergene River was found to be in an oligotrophic state - has high water quality and the middle - downstream of Ergene River were found to be in a eutrophic state - have poor water quality.