Identificação e quantificação de cianobactérias em represas no município de Caxias do Sul - RS

Abstract

The aim of the study was to verify the eutrophic condition and the presence and quantification of cyanobacteria in the main water reservoirs for human consumption in the city of Caxias do Sul-RS. Three drainage basins were selected, with three points in each. Physicochemical measurements were performed at the same time of the sampling, and, photopigment, total phosphate and quantitative and qualitative analysis of cyanobacteria were performed in the laboratory. Cyanobacteria were identified and had their dimensions measured under an optical microscope, with the final result indicated in cells per mL. The results showed that the basins have differences in physical-chemical parameters, and presented differences between points in the same reservoir. The low concentration of total phosphate and photopigments indicates that the reservoirs were not eutrophic, with a low diversity of cyanobacterial genera, being dominated by the genus Microcystis. The quantification of cyanobacteria cells was in accordance with Portaria de Consolidação No. 5 from the Ministério da Saúde, which determines the maximum values allowed in the national territory, but the presence of cyanobacteria, which produce toxins, represents a risk that must be constantly monitored. [resumo fornecido pelo autor]