Abstract
In Europe the monitoring of lakes with regard to benthic diatoms is still conducted in line with the European Water Framework Directive. Ribbon lakes are a special case as extremely steep slopes of the lake basin cause their littoral zone to be narrow. The Durowskie ribbon lake was chosen as a model for the assessment of the ecological status of waters based on its Diatom Index. Given its use in recreation, it is under heavy anthropogenic pressure. Physicochemical and biological parameters were monitored in the peak of the vegetational season (July, August) between 2010 and 2018 at 12 varied littoral sites across the full length of the shoreline. This long-term analysis of the Diatom Index, despite showing an improvement in the quality of water, demonstrated the ecological state of Lake Durowskie to be weak (southern, deep part) to moderate (north, shallow part). The taxonomic structure of diatoms (referral and indicator taxa) in phytobenthos communities allowed to show the changes in physicochemical parameters of the environment such as pH, oxygen dissolved in water and its trophic status. Research results are shown in relation to the anthropogenic changes to the lake’s direct catchment area and the results of the physicochemical monitoring of waters.