Contents of Metals in Sediments and Macrophytes Differed between the Locations in an Alpine Lake Revealing Human Impacts—A Case Study of Lake Bohinj (Slovenia)

Abstract

Metals stored in sediments of lakes can bioaccumulate through the food chain, posing a risk to the environment and human health. Alpine lakes are supposed to be less affected by pollution than lowland lakes and are vulnerable to any changes and impacts in their catchment areas because of their remote position and ultra-oligotrophic character. Therefore, we used a model Alpine lake, Bohinj (in the Triglav National Park, Julian Alps, Slovenia), to evaluate the load of metals in the abiotic and biotic compartments of the ecosystem, in order to assess the spatial distribution of metals, and finally, to determine whether past and present human activities in the lake’s catchment area may be causing pollution. To this aim, the contents of Cu, Pb, Cr, Cd, Co, Mn, Fe, Zn, Hg and Ni in the sediment, water, and macrophyte samples were determined. The results showed that the average content of some toxic elements, especially in the sediments (Cd 0.52 mg/kg; Hg 0.03 mg/kg) and plants (Co 0.71 mg/kg; Cr 5.88 mg/kg) was elevated compared to natural background values. High Hg contents could be connected with natural geological sources, while other elements were probably of anthropogenic origin. High levels of all elements in the eastern part of the lake indicated long-term pollution, which could be a consequence of past iron extraction and military activities in the vicinity. On the other hand, high contents of elements in the water suggests that intensive touristic activities in the area may cause temporal pollution in the summer. The study sheds light on complicated processes governing the distribution of trace metals in Alpine lakes.

Distribution of Aquatic Macrophytes in the Littoral of Lake Bohinj (Slovenia)

“…There is an official bathing area where bathers stir up the sediment, releasing additional nutrients (Table S2). The biotic communities in the substrate are affected by bathers walking around on the substrate, picking off macrophytes and turning over stones [20].…”

“…In this study, we recorded the submerged macrophytes in the entire littoral zone of the Lake Bohinj, with special regard to species identity, cover and environmental characteristics such as substrate type, bottom inclination and water depth, which create different site conditions or even inhibit growth. Macrophyte studies at Lake Bohinj have so far focused mainly on a few sampling plots and transects along the shoreline, and detailed mapping of the entire littoral has not yet been conducted [19,20]. Lake Bohinj is located in the nature-protected area of Triglav National Park.…”