A water quality assessment based on benthic diatoms of the Timok river basin (eastern Serbia) under multiple anthropogenic pressures

The study is focused on diatom communities as indicators of the water quality of aquatic ecosystems. The study included watercourses of the Timok River Basin in eastern Serbia. Sampling of algological material and physicochemical measurements were conducted at 30 locations in September 2016. Non-metric multidimensional scaling (NMDS) showed that conductivity had an effect on the spatial variability of the diatom communities. At locations under influence of acid mine drainage along the Borska river, its tributaries and the Timok river, the diversity of benthic diatoms decreased and the abundance of metal tolerant taxa Achnanthidium minutissimum, Nitzschia capitellata and Nitzschia palea increased. Our study revealed that the combined effect of different pollutants significantly impacted on diatom assemblages; diatoms are good bioindicators of multiple pressures; and diatom indices with different types of pollution, may show an unreliable picture of the actual state, therefore, biological and physico-chemical parameters should also be observed when interpreting the results of a solely diatom-based assessment of the ecological condition of freshwaters