ABSTRACT
Mine drainage water from the Schlenze stream, Mansfeld Region, Central Germany, which have shown an increase in heavy metal concentrations of Cd2+, Cu2+, Pb2+, and Zn2+, was used to investigate the bioremediation potential of charophytes. The removal of heavy metals by Chara subspinosa from the water was tested in single- and multi-metal additions. The uptake capacity of C. subspinosa decreased during the course of the experiment and was higher in single-metal addition than in multi-metal addition of Pb2+, Zn2+, and Cd2+. Accumulation of heavy metals in the carbonate encrustation of charophytes was far lower than those to which they were exposed. Cu, Cd, Pb, and Zn co-precipitated more in the encrustation of C. subspinosa exposed to single-metal approach than to multi-metal approach. The carbonate composition of charophytes was influenced by the water chemistry. Content of Na in the carbonate encrustation correlated with the Na+ concentration of the respective water. The toxic effect of heavy metals on photosynthesis was species-specific. Electron transport rates (ETRmax) were higher in Chara tomentosa than in C. subspinosa. Charophytes withstand the heavy metal concentrations when diluted with river water from the Altarm cut-off lake and can therefore be used for the bioremediation of diluted mine drainage waters by co-precipitating Cd, Cu, and Zn.