Resiliência da comunidade de macroinvertebrados aquáticos após a aplicação dos agrotóxicos nas lavouras de arroz irrigado no Sul do Brasil

Abstract

Agrochemical contamination is the main source of pollution of water resources and a constant threat to the biodiversity and balance of natural ecosystems. In 2008, Brazil became the largest consumer of agrochemicals in the world. Rice cultivation is one of the main activities responsible by the loss of natural wetlands and the increasing use of agrochemicals. In face with this context, this work aimed to evaluate the resilience of the community of aquatic macroinvertebrates after the application of agrochemicals throughout the cultivation cycle in southern Brazil. The specific objectives of this study were: 1) To analyze the variation in richness, abundance and composition of aquatic macroinvertebrates, after the use of agrochemicals,in rice plantations in southern Brazil and compare the results with natural wetlands; 2) To evaluate the concentration and persistence of residual pesticides in water from rice fields and the possible effects over the community of aquatic macroinvertebrates; and 3)To evaluate the relationship between water abiotic variables and the community of aquatic macroinvertebrates. Five samplings were conducted during the rice growing season (2011-2012) in three rice fields and three natural wetlands. A total of 9831 macroinvertebrates distributed in 41 taxa were collected. The Class Insecta represented 49% of total abundance. Macroinvertebrate richness and abundance were higher in natural wetlands than in rice plantations during initial samplings. The herbicide Clomazona showed a negative relation with richness and abundance of aquatic macroinvertebrates. The results support the study hypothesis, which states that agrochemicals affect negatively the macroinvertebrate community and as the residues dissipate in water, the composition of macroinvertebrates becomes more similar between rice fields and natural wetlands. Moreover, the study showed a high sensibility of the macroinvertebrate community to the application of agrochemicals and its possible use as a complementary tool in the evaluation of contamination in aquatic ecosystems.