Ecological status estimation of minimally disturbed rivers of the Akarcay Basin (Turkiye) using diatom indices

Abstract

As suggested by the Water Framework Directive (WFD), in order to determine the ecological status of the rivers, it is necessary to define the reference conditions that can be compared with observed conditions. In this study, selected candidate 17 rivers of the Akarcay Basin (Turkiye) were sampled three times in 2018, and their ecological status was evaluated using 18 different diatom indices. 10 different environmental variables were also sampled combined with diatoms, and alkalinity and total organic carbon were determined as the most crucial pressures for the distribution of diatom assemblages based on the Redundancy Analysis (RDA). Among the diatom indices, Steinberg and Schiefele's Index (SHE), Rott's Saprobic Index (ROTTs), Metric-European Index (CEE), Rott's Trophic Index (ROTTt), Watanabe Index (WAT) and Swiss Diatom Index (DICH) showed significant correlations with alkalinity and total organic carbon according to Multiple Linear Regression (MLR) results. SHE and ROTTs indices showed higher and similar responses to the pressures, and indicated high and good ecological status for sampling sites. Sampling sites with high ecological status can be evaluated in the reference monitoring network for future studies in the Akarcay Basin.