Avaliação de toxicidade de três substâncias de referência ao microcrustáceo Daphnia magna

Abstract

The development of products and technologies has increased significantly, resulting in the release of chemical and physical agents, contaminating the aquatic and terrestrial biota and causing environmental imbalance. The increasing concentration of these residues in aquatic ecosystems has attracted increasing interest, both the quantity and variety, as the toxicity, which can cause damage, even mutagenic in non-target aquatic organisms, thus creating the need for impact assessment these ecosystems. This study aimed to evaluate the possible toxicological effects caused by reference substances (Potassium Dichromate, Copper Sulfate and Potassium Chloride), using the test micro-organism Daphnia magna, by testing traditional sensitivity (toxicological evaluation). Sensitivity tests were performed in laboratory, according to standardized methodologies and some adaptations. The values of EC50-24h calculated for Daphnia magna were 0.82 mg / L for the potassium dichromate and 0.17 mg / L for copper sulfate. The values of EC50-48h calculated for Daphnia magna were 698.8 mg / L for potassium chloride. All substances used provided satisfactory outcomes and attended the purpose of reference substance, having highlighted the potassium chloride whose standardization does not required several changes in methodology as well as being safer with respect to handling and disposal on the environment. As specific objective was proposed assessment of the genotoxic effects by the comet assay, of the three different substances through DNA damage in Daphnia magna from the EC50 found through sensitivity tests. For a few comets have been found by the blade, it was not possible to make statistical calculation of damages, which were difficult to identify. This obstacle can be attributed to the fact that the cellular material of Daphnia magna is very small, making it difficult to visualize any comet in the microscope, even at 100x objective. Besides the cellular material used is too small, there were a lot of loss of material by use of a disintegrator incompatible during preparation of the cell suspension for the comet assay. However the methodology adapted and introduced into the laboratory was used for fishes and showed good results.