Anahí Domínguez

Toxicity of AMPA to the earthworm Eisenia andrei Bouché, 1972 in tropical artificial soil

Aminomethylphosphonic acid (AMPA) - one of glyphosate’s main metabolites - has been classified as persistent in soils, raising concern regarding the widespread use of glyphosate in agriculture and forestry. Glyphosate may have negative or neutral effects on soil biota, but no information is available on the toxicity of AMPA to soil invertebrates. Therefore our aim was to study the effect of AMPA on mortality and reproduction of the earthworm species Eisenia andrei using standard soil ecotoxicological methods (ISO). Field-relevant concentrations of AMPA had no significant effects on mortality in acute or chronic assays. Except at the highest concentration tested, a significant biomass loss was observed compared to controls in the chronic assay. The number of juveniles and cocoons increased with higher concentrations of AMPA applied, but their mean weights decreased. This mass loss indicates higher sensitivity of juveniles than adults to AMPA. Our results suggest that earthworms coming from parents grown in contaminated soils may have reduced growth, limiting their beneficial roles in key soil ecosystem functions. Nevertheless, further research is needed to better understand the mechanisms underlying the sublethal effects observed here.

Effect of Land Use Changes in Eastern Amazonia on Soil Chemical, Physical, and Biological Attributes

Abstract Land use change in rural settlements of the Amazon influences the abundance, diversity, and survival of soil fauna, especially earthworms, affecting the supply of ecosystem services. This study evaluated the effects of forest conversion to pasture on soil attributes and how the changes on the earthworm community affect soil porosity. Soil samples were collected from two toposequences (forest and pasture) at the summit (T1), midslope (T2) and footslope (T3) positions in July 2012 (dry season) and January and March 2013 (wet season). Samples were taken in five replicates at the depths of 0 to 10, 10 to 20, and 20 to 30 cm for determination of moisture, bulk density, total porosity, micromorphometry of pores, surface litter dry matter, chemical properties, and abundance and richness of earthworms. The numbers of macropores and micropores and S index (S) were calculated. The change on land use increased soil organic matter, pH, and calcium and reduced dry matter, moisture, and S index in pasture, as well as the loss of earthworm morphospecies highly related to the maintenance and formation of soil macroporosity, especially large rounded pores and, secondarily, large complex pores. This resulted in a loss of soil physical quality.