Towards rebuilding algae communities in post-mining ditches

• Algae grow on stones in water from two post-mining ditches in laboratory. • The algae were filamentous and one-celled, autochthonous and allochtonous species. • Selected diatom and green algal species can be used as biological starters. • Biological starters are planned to be transfered to post-mining waters. • Biological starters could accelerate the self-purification of the waters. Algae, as organisms known to occur in extreme environments and accumulate pollutants, can be effective in purifying post-mining waters. In our work, we present the first stage of a new method involving the use of indigenous algae in the self-purification process of such waters. Therefore, the specific aims of this paper were: (i) measurements of physical and chemical parameters of two post-mining ditches in the area of ​​Upper Silesia (Southern Poland), (ii) isolation of single indigenous strains from the ditches, (iii) identification of both indigenous as well as allochthonous (from a sewage treatment plant) algae using morphological and genetic characteristics, (iv) increasing their biomass, (v) conducting an experiment to check whether algae grow on the solid substrate in the water from these ditches in the laboratory, (vi) selecting algae for biological starters, i.e. algal mats growing on solid substrate. The biomass of 12 algal taxa, 9 autochthonous and 3 allochthonous, mainly diatoms and green algae, was multiplied. The experiment revealed that several autochthonous one-celled diatoms, especially Pinnularia appendiculata , and filamentous green algae, Klebsormidium nitens and Mougeotia sp., as well as one allochthonous colonial green alga, Pectinodesmus pectinatus , turned out to be the most tolerant to the conditions prevailing in both ditches. These algal taxa were the most important element in the structure of biological starters on solid substrates. In the next stage of our research the potential of the biological starters to remove chemicals occurring in high amounts in post-mining waters should be studied.