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Assessing the effects of L-cyhalothrin and rain events on soil microarthropod community using a Terrestrial Model Ecosystem

2012Assessing the effects of L-cyhalothrin and rain events on soil microarthropod community using a Terrestrial Model EcosystemGONZALEZ MARTINEZ Tanya Marcela (Mexico)
Organisation:University of Coimbra, Coimbra (PT)Supervisor :José Paulo Sousa
Summary: To identify potential risks derived from changing climatic regimes has become a major concern worldwide. Alterations of rain patterns are expected to modify the environmental responses of biological communities in soil, mainly due to alterations in moisture levels, a key factor for soil microarthropods. Pesticide use imposes great disturbances to soil, altering its functional dynamics. As environmental conditions, like rain and temperature regimes can interfere with chemical speciation and/or chemical’s persistence in soil, soil organisms might be affected in a different way in contaminated soil under different climatic scenarios. Lambda-cyalothrin is a pyrethroid insecticide widely used to control insect pests for public health and cultivated lands. Annual agricultural use of L-cyalothrin has increased over the last years, while insecticide residuals have been detected in irrigation and storm-runoff water, and associated sediments as well. The potential risk of this pesticide to aquatic organisms is known to be high, but its effects on terrestrial communities remains practically unknown. Moreover, to date, the combined effect of changes on rain patterns and L-cyhalothrin application has not been investigated. Aiming to fill this gap, a semi-field experiment was performed using Terrestrial Model Ecosystems (TMEs). The effect of different doses of the commercial formulation of Judo® insecticide, containing L-cyalothrin as active ingredient (a.i.), was evaluated in soil fauna communities of a pasture field free of pesticide applications for more than 5 years. Doses of 0, 7.5 and 37.5 g of a.i./ha were investigated, equivalent to 0, 1 and 5 times the recommended dose, respectively. Three replicates per test dose were exposed to different rain regimes to reach moistures corresponding to 30, 50 and 70% of the water-holding capacity of the field soil. After 2 and 8 weeks of insecticide application, soil samples were taken out to characterize soil fauna communities (microarthropods, nematodes, enchytraeids and earthworms). In this study only the results from Collembola are shown and overall they suggest that toxicity levels derived from lambda-cyalothrin applications may be dependent on rain regime. Composition of soil mesofauna community is a good indicator of the influence of pesticides along time under changing climatic conditions.