Cyanobacteria and algae of gold mine tailings in the North-West Province of South Africa

Abstract

Cryptogamic crusts are important components in arid and semiarid lands and could play a vital role in the rehabilitation of mine tailings. The aim of this study was therefore to investigate the occurrence of cyanobacteria and algae on gold mine tailings storage facilities in the Northwest province in South Africa that are characterized by extreme geotechnical and geochemical conditions. Samples for chemical, physical as well as biological analysis were collected from un-rehabilitated tailings as well as a chrono-sequence of biologically rehabilitated tailings materials. Results show that Chlorella (Trebouxiophyceae), Chlorococcum (Chlorophyceae) and Klebsormidium (Klebsormidiophyceae) species were present at all the rehabilitated sampling sites. The dominant genera on these sites were Chlamydomonas (Chlorophyceae), Chlorococcum, Klebsormidium and Phormidium (Phormidiaceae). No cyanobacterial or algal growth was found on freshly deposited tailings material and only a few species such as Chlamydomonas sp., Chlorella ellipsoidea Gerneck, Chlorococcum sp., Microcoleus vaginatus (Phormidiaceae) and a Phormidium species were found on un-rehabilitated material. It was evident that the time of rehabilitation did not have an influence on the algal as well as cyanobacterial species present in the tailings material and that the presence of a grass cover on the rehabilitated sites may have provided a microclimate enhancing the growth of these organisms.