Diatom composition and ecological characteristics of Değirmendere and Bulakli streams according to the European Union Water Framework Directive

Bio-evaluating of surface waters has become more important since the application of the European Water Framework Directive (WFD). Phytobenthos is an important biological quality element suggested by the European WFD in the determination of ecological status of aquatic ecosystems. The present study was aimed to evaluate the limno-ecological conditions of Değirmendere (D1-D3) and Bulaklı (B1 ve B2) streams, using diatom metrics and multivariate approaches according to the WFD requirements. Canonical Correspondence Analysis (CCA) was used to assess the relationships of diatom species and environmental variables from five stations sampled in four seasons. A total of 87 diatom species were identified in two streams during the study period. Achnanthidium druartii, Achnanthidium minutissimum, Amphora ovalis, Cocconeis placentula, Cymbella excisa, Encyonopsis minuta, Encyonema silesiacum, Gomphonema cuneolus, Gomphonema minutum, Gomphonema parvulum, Navicula cryptotenella, Nitzschia denticula and Nitzschia paleawere the commonly found. Electrical conductivity (EC), salinity, oxidation reduction potential, PO4, and TP had an effective role in the distribution of diatom species during the study. The ecological status and water quality of sampling stations in Değirmendere and Bulaklı streams were evaluated using variety of different diatom indices.CCA clearly separated the stations of Değirmendere and Bulaklı streams. While Bulaklı stream stations were associated with EC, salinity, and nutrient salts, Değirmendere stations were localized in the region against. The results showed that the water quality condition of Değirmendere is mostly good and the water quality condition of Bulaklı stream is mostly poor. Diatomic indices (TIT (R2=0.78), TI (R2=0.51), EPI-D (R2=0.60), TWQI (R2=0.45), RRDI (R2=0.44) ve TDI (R2=0.46)) were associated with logTP. The high coefficient value of TIT strengthens the suitability of it for the bio-assessment of Değirmendere and Bulaklı streams.