Results obtained in the thematic project FAPESP 2016/14227-5 demonstrated that: 1) the waters of the alkaline lakes of the Pantanal of Nhecolândia systematically present high concentrations of dissolved As (up to 3000 µg L-1); 2) despite the extreme conditions, these lakes are home to an abundant microbial community; 3) higher dissolved As concentrations are generally found in lakes where the highest autotrophic activity occurs (green lakes) and which consequently have higher organic matter production; 4) the phytoplanktonic organisms in these lakes have a low bioconcentration factor regarding arsenic. This last fact may be due to the ability of microorganisms to tolerate and/or metabolize As, or even due to various processes occurring in the water column that limit As bioavailability (e.g. complexation with organic matter). In any case, phytoplankton seems to play an essential role in the cycle of this element, as it can influence its speciation and bioavailability. This project is part of this framework and aims to elucidate the role of two species of cyanobacteria (Limnospira sp. and Anabaenopsis sp.) in As speciation, bioaccumulation and biotransformation and thus better understand their role in the As biogeochemical cycle in this ecosystem. The two cyanobacteria, previously isolated at the CENA/USP Cellular and Molecular Biology Laboratory from phytoplankton samples collected in alkaline lakes, will be cultivated in this laboratory in a medium enriched with As(V) or As(III). The concentrations of total As and of each As(V), As(III), MMA and DMA species in the different types of samples (culture medium and cells) will be determined by High Pressure Liquid Chromatography (HPLC) coupled with on-line UV irradiation, Hydride Generation and Atomic Fluorescence Spectrometry (HPLC-UV-HG-AFS). Bioconcentration factors will be calculated as the ratio betweenf As concentration in the cells and in the culture medium.
News published in Agência FAPESP Newsletter about the scholarship: