Ecotoxicological assessment of the effects of glyphosate and chlorpyrifos in an Argentine soya field

Abstract

Discussion. The ecotoxicological effects of pesticides can be assessed by monitoring the status of communities in real ecosystems or through the use of laboratory toxicity tests. Litterbag field test showed no influence of the treatments on the organic matter breakdown, suggesting a scarce contribution of soil macrofauna. The bait-lamina test, however, seemed to be useful for detecting the effects of GLY and CPF treatments on the activity of the soil fauna. CPF failed to give significant differences with the controls in the reproduction test and the results were not conclusive in the avoidance test. Although the field population density of earthworms could be affected by multiple factors, the effects observed on the reproduction and avoidance tests caused by GLY could contribute to its decrease, with the subsequent loss of their beneficial functions. Biomarkers measuring effects on suborganism level could be useful to predict adverse effects on soil organisms and populations. Among them, NRRT, a lysosomal destabilization biomarker, resulted in demonstrating more sensitivity than the reproduction and avoidance tests. The Comet assay was responsive only to CPF. Since DNA damage can have severe consequences on populations, it could be regarded as an important indicator to be used in the assessment of soil health. Conclusions.Reproduction and avoidance tests were sensitive indicators of GLY exposure, with the former being more labor intensive. Bait-lamina test was sensitive to both CPF and GLY. NRRT and Comet assays revealed alterations at a subcellular level, and could be considered complementary to the biological activity tests. Because of their simplicity, some of these bioassays seemed to be appropriate pre-screening tests, prior to more extensive and invasive testing.Recommendations and Perspectives. This study showed deleterious effects of GLY and CPF formulations when applied at the nominal concentrations recommended for soya crops. Further validation is needed before these endpoints could be used as field monitoring tools in Argentine soya soils (ecotoxicological risk assessment -ERA tools).

Biomarkers for the assessment of chlorpyrifos effects on earthworms and on soil functional parameters

“…These results contrast with those reported previously for a soybean fi eld on a clay silty soil sprayed with chlorpyrifos (Casabé et al, 2007). Physical structure and chemistry of the soils have a strong infl uence on this functional endpoint, and could account for the observed differences.…”

“…Few studies, however, showed effects on neutral red retention time in earthworms exposed to chlorpyrifos contaminated soils (Hodge et al, 2000;Casabé et al, 2007;Reinecke & Reinecke, 2007). Our results showed that the neutral red retention time was sensitive to the low chlorpyrifos concentrations present in soil, and may constitute an early indication of impending physiological damage in the earthworms.…”

“…Neutral red retention and comet assays revealed alterations at subcellular level, and can be regarded as indicators to be used in the assessment of soil earthworms health. Previous results on a soybean fi eld of the Santa Fe Province, sprayed with chlorpyrifos, showed a similar pattern in both cellular biomarkers (Casabé et al, 2007). In terms of the avoidance, earthworms exposed to soils sampled 14 days after treatment had varied results: when exposed to soils from block 1, earthworms preferred the treated substrate; in contrast, worms tended to avoid treated soils from blocks 2 and 3 (Figure 3).…”

“…The comet assay was performed on the same coelomic fl uid (Casabé et al, 2007). We mixed 10 μL of the coelomocyte suspension with 75 μL of 0.75% low-melting-point agarose at 37ºC, and spread it over a microscope slide precoated with 100 μL 1% normal-melting-point agarose.…”

Genotoxic and reproductive effects of an industrially contaminated soil on the earthworm Eisenia Fetida

“…The study of coelomocytes in earthworms is relevant because these leukocytes, located around the intestinal tract, are particularly exposed to soil pollutants and are involved in the process of cell immunity [Dhainaut andScaps, 2001, Manerikar et al, 2008]. The comet assay applied to earthworms has been used in previous studies to investigate the genotoxicity of artificial or natural soils spiked with dioxins [Verschaeve et al, 1993], heavy metals [Bierkens et al, 1998;Reinecke and Reinecke, 2004;Zhu et al, 2006;Manerikar et al, 2008], pesticides [Zang et al, 2000;Bustos-Obregón and Goicochea, 2003;Xiao et al, 2006a;Casabé et al, 2007], or PAHs [Martin et al, 2005;Zhu et al, 2006]. Yet, studies dealing with the genotoxicity of field-contaminated soils to earthworms are rare [White and Claxton, 2004].…”