Ecological quality assessment of running waters in the North Aegean catchment with diatom metrics and multivariate approach

Assessing ecological quality of surface waters is getting more important to achieve environmental sustainability since the implementation of EU Water Framework Directive. This study was designed to assess ecological quality of freshwater bodies in the North Aegean catchment using the trophic index Turkey (TIT), recently developed for Turkish running water assessment. This first work attempts to evaluate rivers water quality in the Northern Aegean catchment, a touristic region based on the diatom index dedicated to the Anatolia region. Data were taken from 18 sampling stations in the Northern Aegean catchment (Turkey) from August 2014 to August 2015. A canonical correspondence analysis (CCA) performed to evaluate the relationship between diatom assemblages and environmental variables especially nutrients, temperature, electrical conductivity, and biochemical oxygen demand played important roles in the distribution of diatom species. CCA explained 12.5% of the cumulative percentage variance of diatom assemblage's data with 92.8% of the species-environment correlations. In related to the water ecological status, the lowest TIT (1.57) values was recorded in Geyikli creek, whereas the highest TIT (2.82) was calculated in Bakircay stream. The ecological quality ratio changed between 0.58 (Bakircay stream with moderate status) and 0.99 (Geyikli, Kar and Kemer creeks with high status). Pollution tolerant species such as Gomphonema parvulum, Navicula recens, Navicula cryptocephala, Navicula cryptotenella, Navicula trivialis, and Cyclotella meneghiniana characterized the moderate ecological status water bodies were, while the high and good ecological status sites were characterized by nutrient sensitive species such Navicula radiosa, Didymosphenia geminata, Cymbella excisa, and Hannaea arcus. The ecological status the water bodies indicated exactly the state of deterioration of these watercourses due to human activities in the catchment. A significant positive correlation between TIT values and logTP confirmed that this index as a metric is a useful biological tool for the bioassessment of regional water quality.