Lead Impact on the Earthworm Eisenia fetida and Earthworm Recovery after Exposure

This study investigates the effects of lead (Pb) on earthworm Eisenia fetida and its potential to recover from Pb exposure. Adult earthworms E. fetida were exposed for 4 weeks to lead (40–2500 mg Pb kg−1) in soil, and after the period of exposure, earthworms were transferred to clean unpolluted soil for 4 weeks to recover. Pb had no effect on the earthworm’s survival but inhibited earthworm growth; growth rate decreased with Pb concentration in the soil. During the recovery period, Pb pre-exposed earthworms did not manage to recover completely their growth. Lead had a highly significant effect on the malondialdehyde (MDA) concentration during both exposure and recovery periods. Pb showed concentration dependent toxicity relationships (weight, lipid peroxidation) for total earthworm Pb concentration. However, earthworm Pb bioconcentrations after recovery period could not explain the higher MDA concentration and lower earthworm fresh weight. Earthworms pre-exposed to low Pb levels have the potential to recover their growth and decrease Pb bioconcentrations, though more prolonged recovery period is needed to full recovery.