Resistência de duas espécies de algas verdes aos íons FE3+ e CU2+ para uso em processos de biorremediação em ambientes contaminados por metais

Abstract

Metals are wildly used in society and they extraction and/or incorrect disposal can result in environmental contamination, which can be a big problem since they are potentially toxic to humans and other beings. Iron and copper are two of the most used metals and, therefore, most explored. Bioremediation is a technic to remove metals, with algae and cyanobacteria being used to efficiently adsorb, absorb and accumulate metals due to their morphological and structural characteristics. Since these organisms need to exposed to high concentrations in bioremediation, it’s necessary to identify which species are more resistant. However, studies focusing on copper usually evaluate the effects of low concentrations and the ones focusing on iron are rare. In this study, a comparison of methods in studies about Fe or Cu toxicity on algae and cyanobacteria was made, since those can interfere with the metal toxicity. 18 articles about Cu were found and only 03 about iron. All were different regarding the culture medium, few used EDTA and most lack information about pH correction. Next, experiments related to Fe and Cu toxicity were made with Desmodesmus armatus and Monactinus simplex, testing their resistance to high concentrations of these metals. The species were cultured in CHU10 medium with the addition of five concentrations of Fe or Cu, between 1 and 81 mg/L, and with addition of EDTA proportional to the metal concentration to avoid its precipitation. An EDTA control was also made. The iron precipitated, even with EDTA, but copper remain dissolved. The cell density was measured every 24h through optical density at 440 nm, for 72h total. Both species grow like in the control in mediums with either Fe or Cu. However, the highest concentration of Fe and Cu resulted in growth similar to the EDTA control, with the lowest growth of all treatments. The lack of standardization in tests make it harder to compare studies. It is essential to standard both medium and its pH, since both can interfere with metal toxicity. The great resistance of the algae to the metals is possibly related with the use of EDTA, which diminishes to availability of free ionic metal and, therefore, its toxicity. Both species seems to have potential to be used in process of bioremediation.