In the context of Action B3, the BETA Technological Center have performed an experiment in artificial streams to evaluate the effects of an hypersaline mining effluent on freshwater ecosystems at different concentrations, using the aquatic biofilm as a bioindicator.
The hypersaline mining effluent used in this study simulated a mining effluent from a real abandoned potash mine located in Menteroda (Germany), characterized by an extreme salinity. In this abandoned mine, leaching waters are currently stored in a reservoir from which they can reach the surface waters by flowing through embankments or through the base of the tailing pile. In this experiment, we simulated the entrance of these leaching waters into a receiving stream at different salinity concentrations and we evaluated the biofilm response along this salinity gradient (3, 6, 15, 30 and 100 g/L). This experiment was performed in artificial indoor channels under controlled temperature and light conditions.
Specifically, biofilm growth on artificial substrata was exposed during 3 weeks to the salinity gradient, and during this period, different structural and functional parameters were evaluated (community composition, diatoms, photosynthetic efficiency, phosphorous uptake rate, microrespiration, chlorophyll-a and ash free dry mass). After the exposure period, we added clean water for 2 weeks to test if the communities were able to recover.
Preliminary results obtained in this study indicated that high salinity concentrations, similar to those caused by mining effluents from potash mining activities, severely affected both the structure and functioning of the aquatic biofilm in streams, whereas low salinity concentrations could stimulate its functioning without significant changes in its structure.