Effects of Water Pollution on Diatom Communities of Roșia Montană Mining Area, Romania

We investigated the diatom communities and physicochemical water variables in the Abrud River catchment area (the Roșia Montană mining area, Romania) at 16 sampling sites, some of them impacted by acid mine drainage (AMD) and heavy metals. Diatoms serve as effective indicators of water characteristics owing to their ubiquity and sensitivity to environmental variables. This study aimed to enhance the understanding of the key environmental factors influencing the diatom flora of polluted rivers across various spatial and temporal scales, thereby informing the optimization of ecosystem management strategies. This work contributes to the knowledge of Romanian diatom flora through the identification of 274 taxa belonging to 63 genera, including 35 taxa recorded for the first time in the country. The spatial and temporal variations in the species richness patterns highlighted the effects of water pollution resulting from past mining activities, revealing distinctions between the main Abrud River stream and its tributaries, some of which exhibited extremely low species richness with few or no identified taxa. This contrasted sharply with the cleaner upstream waters of the Roșia Valley, where a notably rich diatom community (85 taxa) persisted, highlighting the severe localized impact of mining discharges on biodiversity.