Efeito dos herbicidas diuron, glifosato e paraquat e curvas de distribuição de sensibilidade de espécies (CDSE) para a proteção da diversidade de macrófitas aquáticas da região Amazônica.

Abstract

The aquatic ecosystem of the Amazon has been the target of environmental contamination by the indiscriminate use of herbicides, endangering diversity and abundance of aquatic macrophytes in the region. Little is known about the effects of herbicides on species of aquatic macrophytes occurring in the Amazon, most ecotoxicological studies are conducted with Lemna sp. species which is used as representative of the effects of pesticides on the community of macrophytes. In addition, the maximum permissible values for the herbicides in use in Brazil are not established by law. This work aimed to investigate the chronic toxicity of diuron, glyphosate and paraquat in seven species of Amazonian aquatic macrophytes (Azolla filiculoides, Cabomba aquatica, Limnobium laevigatum, Pistia stratiotes, Phyllanthus fluitans, Salvinia auriculata, Spirodela polyrhiza), allowing to outline strategies for their protection based on the use of the method of distribution of species sensitivity and suggest maximum allowable values for each herbicide. First, the median effect concentration (EC50) of the herbicides tested individually for the seven species was determined, followed by the calculation of the concentrations of risk affecting 5% of species (HC5) using the concept of species sensitivity distribution (SSD). The maximum allowable values for each herbicide in aquatic environments in the Amazon have been proposed. Based on the results of EC50, paraquat was more toxic, followed by glyphosate and diuron, and the species S. auriculata e A. filiculoides were more sensitive to exposure to the herbicide, whereas C. aquatica showed lower sensitivity. HC5 values showed that the Amazonian species are more sensitive than the standard species Lemna sp.. HC5 values generated with the construction of the SSD have been proposed for formulating standards for water quality, with respect to the group of aquatic macrophytes, being the maximum values suggested of 0.06 μg/L, 0.18 μg/L e 0.33 μg/L to glyphosate, paraquat and diuron, respectively. Therefore, this work is one of the pioneers in performing toxicity tests on aquatic macrophytes with herbicides in the Amazon region, thus contributing to increase the number of ecotoxicological data.vIt also serves as a starting point for discussions involving the determination of maximum allowable values herbicide to the aquatic environment of the Amazon aimed at protecting this group.