Tolerance of Ulothrix sp. LAFIC 010 (Chlorophyta) against high concentration of metals from acid mine drainage

The production of acid mine drainage of (AMD) is one of the main phenomena responsible for much of the degradation of water and soil resources. Organisms present at sites contaminated by AMD can have the potential to bioaccumulate heavy metals, stimulating their application in bioremediation processes. Ulothrix sp. LAFIC 010 was identified among the species of algae isolated from water contaminated by AMD in the region of Sideropólis (Brazil). The present study evaluated its tolerance and bioaccumulation potential related to zinc, manganese and nickel. Experiments were performed to see the effects of different concentrations of Zn, Mn and Ni (individually and in combination) on the physiological performance of the alga. The results showed that only the cultures submitted to concentrations above 0.55 mM Zn showed a decrease in growth rate and damage to physiological processes. There was no observed effect of Mn and Ni on Ulothrix sp. LAFIC 010 physiology, even with an 8-fold increase in concentrations of these metals in the medium. In cultures with combined metals, only the treatments with the highest concentrations of Zn presented reduced growth, regardless of the presence of other metals. Additionally, we observed that Mn and Ni did not decrease the toxic effect of Zn. Mn accumulation was indicated in the cell wall and Ni in the vacuole. Our results suggest that the distribution of this alga in contaminated medium is not affected by the concentration of Ni and Mn, at least under the pH that was evaluated. We conclude that Ulothrix sp. LAFIC 010 tolerates and grows under conditions with higher metal concentrations than previously reported for AMD.