Avaliação ecotoxicológica do Rio Uruguai e efluentes pré e pós aplicação de pesticidas utilizando Caenorhabditi elegans como biomonitor

Abstract

The Uruguay River is the most important river in the west of Rio Grande do Sul, separating Brazil from Argentina and Uruguay. The river supports fishing activities and provides potable water for the population, however, pollution is a worrying issue due to anthropogenic activities such as agriculture. The region is known for abundant rice crops, being one of the main rice-producing cities, but also for the application of large volumes of legal and illegal pesticides, because it is a border region. In the long term, this practice may cause irreversible damage due to accumulation of waste, including in the aquatic environment. Thus, our study had as objective to analyze the possible changes of three water points of the municipality before and after the time of planting and application of pesticides, such as the Uruguay River, the Salso stream located in BR 472 and a dam located near crops of rice. In order to biomonitor the aquatic environment, we used the free-living nematode Caenorhabditis elegans, which were exposed for 24 h to the shaken samples and transferred to the solid medium to perform survival, longevity and reproduction tests. In the pre-pesticide samples, we observed that even if the presence of pesticides was not detected properly, the analyzes indicated the presence of metals in the collected waters. In the samples obtained after the application period the analyzes showed the presence of Tebuconazol, Imaetapir, Clomazone, interestingly, the metals described in the pre-pesticidal samples were not reported in the post-samples. We observed that both the survival and the reproductive viability of the worms exposed to the pre- and post-pesticide samples were altered in relation to the control, indicating that both the Uruguay River and other watercourses are contaminated and not only by the presence of pesticides, the size of the population was also significantly reduced in comparison to the control group in the samples obtained after planting. This work illustrates the importance of studies in the field of ecotoxicology, due to the continuous pollution of the environment and the impact that this can cause to the organisms that live in it.