Variation in the Chemical Sensitivity of Earthworms from Field Populations to Imidacloprid and Copper

摘要

The chemical risk of pesticides for nontarget soil macroorganisms has mainly been assessed using the compostearthworm Eisenia fetida. However, E. fetida does not occur in agroecosystems, and it is generally less sensitive than otherearthworm species. Thus, the extrapolation of its response to pesticides to other earthworm species may lead to uncertaintiesin risk assessment. Because toxicity data for other earthworms are scarce, we assessed the chemical sensitivityof five species (Allolobophora chlorotica, Aporrectodea caliginosa, Aporrectodea longa, Aporrectodea rosea, andLumbricus rubellus) from different habitats (forests, wetlands, and grasslands), as well as E. fetida, to imidacloprid andcopper in single‐species acute toxicity tests. In addition, we examined the relationship between earthworm traits (ecotypeand weight), habitat characteristics (ecosystem type and soil pH), and chemical sensitivity. The lower limits of the hazardousconcentration affecting 5% (HC5) of species were 178.99 and 0.32 mg active ingredient/kg dry weight for copperand imidacloprid, respectively. Some concentrations that have been measured in European agroecosystems for bothpesticides were above the HC5s, indicating toxic risks for these organisms. Furthermore, soil pH from the sampling habitatplayed a significant role, with earthworms sampled from extremely acidic soils being less sensitive to copperthan earthworms from neutral soils. In addition, endogeic earthworms were more sensitive to imidacloprid than epigeicearthworms. This may translate to changes in soil functions such as bioturbation, which is mainly carried out by endogeicearthworms. Our results suggest that risk assessment should include a wider range of earthworms covering differenthabitats and ecosystem functions to achieve a better protection of the biological functions carried out by these key soilorganisms.