The ability to recover to original states after disturbances makes macroinvertebrates useful tools for assessing the impacts of pesticides. Many studies showed that direct exposure to pesticides decreases macroinvertebrate richness and alters their composition. The main objective of this study was to assess recovery patterns in macroinvertebrate communities after pesticide application in irrigated rice fields. We analyzed short-term temporal dynamics of macroinvertebrate communities after application of the herbicides bispyribac-sodium and clomazone and the insecticide chlorantraniliprole, over the rice-growing season in southern Brazil. We selected three conventional rice fields and the recovery of macroinvertebrate communities was also compared with three adjacent natural ponds. The study was developed from November 2011 to February 2012 (rice-growing season). Five macroinvertebrate collections were carried out 3, 7, 14, 38, and 60 days after pesticide application (November 25). Rice fields showed lower richness and abundance than ponds in the period immediately after pesticide application, and recovery rates in the richness of macroinvertebrate communities were more conspicuous as pesticide residuals dissipated from the fields. Macroinvertebrate community structure in rice fields also became more similar to natural ponds as pesticide traces were scarcer. However, macroinvertebrate abundance patterns were not related to pesticide concentrations in the fields. Our results supported the general hypothesis on the negative effects of pesticide application on macroinvertebrate community in irrigated rice fields, although other environmental features (e.g., length of the flooded period) also contributed to explain temporal dynamics in the macroinvertebrate communities from irrigated rice fields.
Small wetlands are strongly bound to surrounding terrestrial habitats, so understanding their suitability after conversion to human land uses is critically important to produce an ecologically centred planning for amphibian species. Here, we explored how responses of amphibian assemblage to habitat conversion were influenced by reproductive modes in freshwater coastal wetlands in southern Brazil. We also assessed whether species from different biomes are affected in different ways by land conversion. Using data from tadpole assemblages in a transition zone between Atlantic Forest and Pampa, we tested the hypothesis that aquatic modes would be more affected by habitat conversion than are foam-nest species. Overall, quantitative data were influenced by the percentage of crop area, whereas assemblage structure derived from presence–absence data was associated with biome type. Species with aquatic egg-laying were influenced by the percentage of crop area, and many species were more abundant in ponds surrounded by up to 15% crop area in a 1000-m radius. However, foam-nest species were not influenced by any variable investigated (crops, planted pastures, urban areas and biome). This study has highlighted that agricultural conversion poses environmental filters to amphibian communities, selecting species according to some traits (adult reproductive strategies and tadpole plasticity).
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