Bioassessing ecological status of surface waters in the Araban-Yavuzeli catchment (Turkey): application of diatom indices

Abstract

Within the scope of the European Union Water Framework Directive, diatom assemblages as biological quality componentswere used to evaluate the ecological status of 12 surface waters in the Araban-Yavuzeli catchment between October 2013 and October2014. A total of 75 diatom species were identified during the study period. Amphora ovalis, Denticula elegans, Gomphonema parvulum,Gomphonema truncatum, and Navicula cryptocephala were commonly observed. The relationship between diatom assemblages andenvironmental factors was assessed by canonical correspondence analysis and weighted average regression. Dissolved oxygen, temperature, nitrate, biological oxygen demand, lead, and copper played significant roles in the distribution and composition of diatomassemblages (P < 0.05). The ecological status of the stations in Araban and Yavuzeli was characterized using the trophic index-Turkey(TIT), trophic index (TI), and eutrophication and/or pollution index-diatom (EPI-D) indices. According to the TIT, Ardıl Creek1 hadvery good ecological conditions and was characterized by the occurrence of pollution-sensitive diatom taxa (e.g., Cymbella affinis, Encyonema silesiacum, Navicula radiosa), indicated by multivariate analyses. The significant positive correlation of the TIT (P < 0.01, r =0.789) with logPO4 indicated that TIT may be used as an appropriate diatom metric to assess the ecological status of surface waters inthe Araban-Yavuzeli catchment.