Avaliação da fitotoxicidade e ecotoxicidade do extrato bruto de Microcystis aeruginosa

Abstract

Cyanobacterial blooms caused by the species Microcystis aeruginosa, producer of the microcystin-LR toxin, occur frequently in eutrophic water bodies, can cause damage to aquatic organisms and terrestrial plants. The objective of this work was to evaluate the acute phytotoxicity in Lactuca sativa (lettuce) and Sinapis alba (mustard), the acute ecotoxicity in Daphnia magna and chronic in Desmodesmus subspicatus of the crude extract of M. aeruginosa obtained from laboratory culture. In the phytotoxicity assays, germination and root growth were evaluated, and CO2 production was measured by the respirometric method. The acute toxicity tests with D. magna and chronic D. subspicatus were performed according to ABNT standards 12713: 2016 and 12648: 2011, respectively. The crude extract of M. aeruginosa significantly inhibited the growth of mustard rootlets with p <0.01 in the Student's TTest, this response may be related to inhibition of phytormons that regulate the initial development. While for the lettuce seeds there was no inhibition in root elongation, possibly linked to oxidation, by detoxifying enzymes, microcystin-LR or other secondary metabolites. In the respirometry the inhibition of the initial development in mustard was confirmed with lower CO2 production compared to the negative control. In lettuce it was observed a change in the respiratory rate, evidencing physiological effects in its development. In D. magna the crude extract of M. aeruginosa was toxic only in its pure form, causing 76% immobility. For D. subspicatus there was inhibition of growth in concentrations of 25%, 50% and 100% of extract.