Toxicity of lead pollution to the collembolan Folsomia candida in Ferri-Udic Cambosols

Toxic effect of lead (Pb) pollution on Collembola in soils has seldom been studied in depth, which is especially true for growth responses since the juveniles are very small and numerous. A single species test was conducted using the collembolan Folsomia candida as the indicator species, and soil Pb pollution (at Pb concentrations of 0, 300, 600, 1 200, 2 400, and 4 800 mg kg^-1) was simulated by mixing Pb(NO₃)₂ with a natural unpolluted soil. Adult survival, reproduction, body length, and body Pb concentration were determined. Adult survival and reproduction started to decrease at soil Pb concentrations of 1 200 and 600 mg kg^-1, respectively. Lead concentrations in adult and juvenile bodies increased with increasing Pb concentration in soil. The percentage and individual abundances based on body length analysis showed that the larger adults (2.1-2.6 mm, P < 0.01) were more sensitive to soil Pb concentration than the intermediate (1.9-2.1 mm, P < 0.001) and smaller (1.7-1.9 mm, P < 0.001) adults. Similarly, the larger juveniles (1.0-1.4 mm, P < 0.001) were more sensitive to soil Pb concentration than the intermediate (0.6-1.0 mm, P < 0.001) and smaller (0.3-0.6 mm, P < 0.001) juveniles. For both adults or juveniles, the abundance and percentage of larger individuals declined significantly with increasing soil Pb concentration, suggesting that larger individuals were more sensitive to soil Pb pollution. Therefore, body length features, especially the percentage and abundance of larger individuals, would be potential bio-indicators of soil Pb pollution and possibly other types of soil pollution.