From river to sea: ecotoxicological profile of 2,4-D, diuron, glyphosate, herbicides and their mixtures in the aquatic organisms

Abstract

The challenges of agriculture to meet the growing population demand observed in recent decades have incorporated a number of new elements into agricultural practice. In this sense, we highlight the intensification of pesticide use as a way to provide a better yield of agronomic productivity. However, extensive use of pesticides can have, in addition to harmful effects on human health, a major impact on reducing biodiversity. Thus, the presence of toxic compounds in aquatic and terrestrial ecosystems, and the possible effects on non-target organisms, has become a matter of global relevance. Among the most commonly used pesticides in agriculture are herbicides, especially 2,4-D (2,4-dichlorophenoxyacetic acid), diuron (3- (3,4-dichlorophenyl) -1,1-dimethylurea) and glyphosate (N- (phosphonomethyl) glycine). Such herbicides are among the most used in the states of Paraíba and São Paulo; The last two being widely used in sugarcane (Saccharum spp.), an agricultural crop that has high social and economic relevance in both states. Studies show that over 98% of pesticides used can reach non-target species and become pollutants of air, water and soil. Thus, pesticide pollution can affect both terrestrial and aquatic ecosystems. However, despite the growing knowledge about pesticide contamination of aquatic environments, studies on the impact of this class of contaminants on aquatic organisms are still incipient, especially considering marine species. Thus, contemporary ecotoxicology has advocated the design of experimental studies that contemplate a realistic approach to the ecotoxicological scenario. In this context, three aspects, in particular, have been preponderant: 1) the inclusion of species of different taxa in the same study; 2) exposure of organisms to environmental concentrations of contaminants; 3) exposure of organisms to the mixture of contaminants. In addition, the toxicity of a pollutant is related to its behavior in the environment, being dependent on several factors, such as salinity, temperature, pH, presence of organic matter or other contaminants, besides the inherent physiology of the organisms themselves. Thus, studies on the toxicity of contaminants in species from different ecosystems are crucial. In line with these peculiarities, it is important to design ecotoxicological studies that include not only distinct ecosystem species, but also different toxicological targets, in order to provide valuable information about the ecotoxicological profile of the contaminants. Given the above, the present project intends to investigate the effect of three economically, socially and toxicologically relevant herbicides (2,4-D, diuron and glyphosate) - and their mixtures - on embryonic / larval development and two crucial defense systems for homeostasis / survival of aquatic organisms: the xenobiotic resistance (MXR) phenotype and the innate immune system; using as experimental models crustaceans (Artemia franciscana), bivalves (Crassostrea gasar), echinoderms (Echinometra lucunter and Mellita quinquiesperforata) and fish (Danio rerio). Thus, the project aims to cover different taxa and environments, and investigate the impact of herbicides on marine species that make up the Brazilian fauna (E. lucunter, M. quinquiesperforata, C. gasar). The project also proposes, based on various cell and molecular biology techniques, to investigate the mechanisms of toxicity, and contribute to the understanding of the ecotoxicological profile of herbicides and the identification of potential molecular biomarkers and / or indicator species for environmental monitoring. (AU)