Avoidance of Cu- and Zn-contaminated soil by three ecologically different earthworm species

Earthworm avoidance response to soils contaminated with harmful substances has been proposed as a potential tool for assessing soil toxicity with low test effort. In the present study, the objective was to find out whether three ecologically different earthworm species, Aporrectodea tuberculata (Eisen), Lumbricus rubellus (Hoffmeister), and Dendrobaena octaedra (Savigny), avoid soils simultaneously spiked with Cu and Zn. In addition, metal-contaminated field soil taken close to a Cu-Ni smelter was tested with A. tuberculata using a two-section avoidance lest procedure. All three earthworm species clearly avoided Cu/Zn contaminated soil but differently: D. octaedra was the most sensitive species, responding to low metal concentrations, whereas L. rubellus responded only to the highest metal concentration tested, being the least sensitive species. Moreover, A. tuberculata showed clear avoidance response to the metal contaminated field soil. In conclusion, the results indicate that earthworm avoidance behavior is an ecologically relevant parameter for assessing harmfulness of metal contaminated soils, both spiked and field-contaminated soils. However, it is important to consider the specific species to be used in the earthworm avoidance test procedure.