Lead tolerance in Aporrectodea rosea earthworms from a clay pigeon shooting site

Lead tolerance in individuals of the earthworm species Aporrectodea rosea collected from a clay pigeon shooting site was investigated. Lead concentrations in the shooting site soil and the un-shot control site were 6410±2250 and 296±98 mgPb kg−1 dry weight, respectively. Of these concentrations 1050±240 and 12±9 mgPb kg−1 dry weight were suggested to be available, using ammonium acetate (1 M), respectively. With respect to earthworm body burdens of lead the shooting site earthworms had a body burden of 6.1±1.2 mgPb g−1 dry weight while the uncontaminated site earthworms had almost a 1000-times lower body burden of 7.1±9.0 μgPb g−1 dry weight. Lead tolerance was assessed in uncontaminated soil that had been augmented with lead, using lead nitrate solutions, to obtain lead concentrations in soil of 0.5, 5 and 50 mgPb kg−1 dry weight. Earthworms were exposed for 28 days during which time a semi-qualitative assessment was made of their condition. Results showed no decrease in condition in the shooting site earthworms with increasing exposure time or concentration. In contrast, earthworms collected from an uncontaminated site showed a significant (p<0.05) decrease in condition when exposed to lead concentrations above, and including, a concentration of 5 mg kg−1 dry weight soil. These results suggested lead tolerance in the shooting site earthworms.