The effect of lead-contaminated soil from Canadian prairie skeet ranges on the neutral red retention assay and fecundity in the earthworm Eisenia fetida.

Abstract

The sublethal effects of lead (Pb) on the earthworm Eisenia fetida were evaluated in the laboratory using freshly spiked soil and soil collected from Canadian prairie skeet ranges. After a four-week exposure to soil spiked with lead acetate, earthworm neutral red retention time (NRRT). soil Pb concentrations, and earthworm Pb body burdens were measured. Lysosomal NRRT was reduced in a concentration-dependent manner (p < 0.0001), and NRRT was negatively correlated with earthworm Pb body burdens (r = -0.80, p < 0.0001). To evaluate the effects of aged Pb, earthworms were exposed to soil from three skeet ranges, and responses were compared with three matched reference sites. After a four-week exposure, NRRT, growth, fecundity, soil total Pb levels, and earthworm Pb body burdens were measured. The potentially bioavailable fraction of Pb in these sites was measured using a Ca(NO3)2 extraction. Growth and fecundity did not differ significantly between any of the skeet ranges and their reference sites. However, NRRT was significantly reduced in all three ranges compared with their respective reference sites (p < 0.05), indicating that the neutral red retention assay (NRRA) may be useful for detecting toxicity and potential hazards at Pb-contaminated sites. Lysosomal NRRT was negatively correlated with soil Ca(NO3)2-extractable Pb (r = -0.80, p < 0.0001) and soil total Pb (r = -0.73, p = 0.001). Lysosomal NRRT was negatively correlated (r = -0.67, p < 0.002) with earthworm Pb tissue levels.