Interactive effects between earthworms and maize plants on the accumulation and toxicity of soil cadmium

Multi-species tests are preferable in ecotoxicological studies as they allow the investigation of the influence of ecological interactions on mobility, bioavailability, and toxicity of contaminants. We performed monospecific and combined culture experiments in a soil-maize-earthworm testing system to determine the interactive effects between earthworms and maize plants on the accumulation and toxicity of cadmium (Cd) to each respective species. It was found that the co-presence of maize plants and earthworms in soil promoted the mobility and availability of Cd, but reduced Cd accumulation in earthworms and maize roots and showed little effects on cadmiumʹs accumulation in maize stems and leaves. The presence of plants reduced Cd toxicity to earthworm cocoon output and body mass development, while the presence of earthworms showed no significant effects on Cd toxicity to maize shoot and root biomass. Meanwhile, the presence of earthworms reversed the effects of Cd on soil microbial community and stimulated and increased maize rhizosphere microbial species. It was concluded that the increase of metal mobility and availability in a multi-species testing system does not necessarily indicate a corresponding increase of ecotoxicity, and the interspecific effects between species belonging to different trophic levels on the accumulation and toxicity of metals should be taken into account in ecotoxicological risk assessment.