Determination of ecological status of freshwaters and ecological preferences of algae in the Western Mediterranean Basin (Turkey) using multivariate approaches

Several methods have been recently developed for water bioassessment. However, combining these methods to provide a realistic estimation of water quality is rare. The aim of this work was to assess freshwater quality using algae and multivariate approaches. Data were collected from 34 stations in the western Mediterranean basin of Turkey. A total of 206 phytoplankton and 102 diatom taxa were recorded in lentic and lotic systems respectively. Canonical correspondence analysis indicated that environmental variables influenced the distribution of algal taxa. In related to water quality, lakes and reservoirs showed moderate, good and high status according to Phytoplankton Trophic Index (PTI), Mediterranean Phytoplankton Trophic Index (Med-PTI) and the assemblage index (Q). Running waters showed poor to high ecological status based on Trophic Index Turkey (TIT). With regard to the trophic state, the lentic systems varied from oligotrophic to hypertrophic. It appears from this study that combining these metrics could be a useful approach for freshwater bioassessment. However, the use of these indices could lead to wrong interpretation of water quality because of ecoregional changes in algal composition, and there is a need to develop a national phytoplankton based metrics. Besides, TIT should be revised to include all diatom communities from various water types to extend its applicability to a number of aquatic systems.