A new diatom index to assess ecological quality of running waters: a case study of water bodies in western Anatolia

¹ Department of Biology, Faculty of Art and Science, University of Gaziantep, 27310 Gaziantep, Turkey
² T.R. Ministry of Forestry and Water Affairs, Directorate General for Water Management, Ankara, Turkey

^* Corresponding author: celekli.a@gmail.com

Received: 3 May 2017
Accepted: 14 June 2017

Abstract

Diatoms are an important part of aquatic biodiversity and the main component of phytobenthos. They play a key role in aquatic ecosystems and indicate water quality. The European Union Water Framework Directive requires that phytobenthos be used for the ecological quality assessment of water. This study evaluated the ecological status of various watercourses in the western Mediterranean basin of Turkey using a multivariate approach and presents a new trophic index Turkey (TIT) based on diatom assemblages. Twenty-five running water bodies were seasonally monitored for biological and physicochemical analyses from summer 2014 to summer 2015. A total of 102 species belonging to 22 genera were recorded. Cymbella excisa Kützing, Gomphonella parvula (Kützing) Rabenhorst, Ulnaria ulna (Nitzsch) Compère, and Cocconeis communis f. placentula (Ehrenberg) Chmielevski were the most commonly found species. A canonical correspondence analysis was used to examine the relationship between species and environmental factors. The most effective explanatory factors, including nitrate nitrogen, electrical conductivity, altitude, total nitrogen, orthophosphate, and calcium carbonate significantly influenced the ecological preferences of diatom species in the ecosystems. TIT values ranged between 1.53 in Kaya creek and 2.73 in Dalaman stream (A8). Ecological status of water bodies was assessed using an ecological quality ratio based on trophic index Turkey (EQR-TIT) for each of the stations. EQR-TIT ranged from 0.44 in Dalaman stream (A8) to 0.99 in Kocabük creek during the study period. TIT had a high correlation coefficient (R²=0.77) with log total phosphorus  and may be an appropriate diatom metric to assess the ecological status of water bodies.