Ref ID : 4953
Mark Currie, Mark E. Hodson, Rebecca E. Arnold, and Caroline J. Langdon; Single Versus Multiple Occupancy-Effects on Toxicity Parameters Measured on Eisenia fetida in Lead nitrate-Treated Soil. Environmental Toxicology & Chemistry 24(1):110-116, 2005
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The mortality (7 and 14 days), weight change (7 and 14 days), and metal uptake of Eisenia fetida (Savigny, 1826) kept in Pb(NO3)2-treated Kettering loam soil in single- and multiple-occupancy (10 earthworms) test containers were determined. The number of earthworms to dry mass (g) ratio of soil was 1:50 in both sets of test containers. Lead concentrations were in the nominal range of 0 to 10,000 mgPb/kg soil (mg/kg hereafter). Levels of mortality at a given concentration were statistically identical between the single- and multiple-occupancy tests, except at 1,800 mg/kg, at which significantly (p< /_0.05) more mortality occurred in the multiple-occupancy tests. Death of individual earthworms in the multiple-occupancy tests did not trigger death of the other earthworms in that soil. The LC50 values (concentration statistically likely to kill 50% of the population) were identical between the multiple- and single-occupancy soils: 2,662 mg/kg (2,598-2,984, 7 days) and 2,589 mg/kg (2,251-3,013, 14 days) for the multiple-occupancy soils and 2,827 mg/kg (2,443-3,168, both 7 and 14 days) for the single-occupancy soils (values in brackets represent the 95% confidence intervals). Data were insufficient to calculate the concentration statistically likely to reduce individual earthworm mass by 50% (EC50), but after 14 days, the decrease in earthworm weight in the 1,800 and 3,000 mg/kg tests was significantly greater in the multiple- than in the single-occupancy soils. At 1,000, 1,800, and 3,000 mg/kg tests, earthworm Pb tissue concentration was significantly (p< /_0.05) greater in earthworms from the multiple-occupancy soils. The presence of earthworms increased the NH3 content of the soil; earthworm mortality increased NH3 concentrations further but not toxic levels.