Application of epilithic diatoms in the ecological assessment of mountain rivers: contribution to the development of biomonitoring tools for Montenegrin aquatic ecosystems using the case study of the Tara River

The diversity, structure and ecology of the epilithic diatom assemblage from a mountain river (Tara River) were studied in two seasons in 2015. A total of 52 diatom taxa were identified. The most abundant taxa were: Achnanthidium minutissimum, Gomphonema olivaceum var. minutissimum, Cymbella affinis, Diatoma vulgaris and Fragilaria capucina, reflecting the calcareous geology of the catchment. The absence of significant spatial differences between diatom assemblages could be attributed to the lack of longitudinal variation in the investigated river sections in terms of geology, slope and water chemistry. The mean diatom density in summer (29960 cells cm(-2)) was significantly higher than in the spring (3200 cells cm(-2)). The selected diatom indices (TDI and BDI) indicated a very good water quality of the Tara River. The upper part of the Tara River could be considered as a potential reference site against which other high altitude calcareous rivers and streams of Montenegro could be evaluated. The high degree of concordance between selected diatom indices and water quality variables (e.g., nutrients) observed in the study, proved applicability of epilithic diatoms in ecological assessments of Montenegrin mountain rivers. Nine taxa were recorded for the first time in Montenegro: Achnanthidium biasolettianum, A. subatomus, Adlafia minuscula, Amphora inariensis, Cymbella leptoceros, Cymbopleura subaequalis, Gomphonema pumilum, G. subtile and Sellaphora laevissima.