ASSESSMENT OF ECOLOGICAL STATUS AND WATER QUALITY BY USING SOME TROPHIC INDICES IN A DAM LAKE

The composition and seasonal variations of benthic diatoms of Yedikir Dam Lake were studied using samples collected from two stations between November 2004 and April 2006. The diatom communities were diverse: 81 taxa were found, belonging to the Bacillariophyta. In two sampling stations, the most important occurrence was suddenly the increase of epipelic diatoms in May 2005. It was drived from especially three species; Nitzschia fonticola, Navicula veneta and N. capitata var. hungarica. Trophic Diatom Index (TDI) provides information about trophic levels of the aquatic ecosystem. The water quality of Yedikir Dam Lake in terms of trophic levels was determined according to these 81 diatom taxa by calculating TDI. In particular, it is important that sites in the 'station 2', where the water enters dam from Tersakan stream, are chosen so that the influence of the gross effects of organic pollution on the index is minimised. According to Trophic classification and diversity (TSI, TDI), respectively, ascribed Yedikir Dam Lake to the eutrophic range. Multivariate analyses indicated that both the regional distribution and seasonal variation of benthic diatoms are mainly driven by nutrient concentration. Diatoms are predominantly affected by geochemical characteristics including pH and mineralisation level.