Exposure to mercury reduces cold tolerance in the springtail Folsomia candida

We investigated how mercury (Hg) as an example of a widespread pollutant, can influence the tolerance of low temperature stress in the springtail, Folsomia candida. Springtails were exposed to aqueous solutions with a range of concentrations of HgCl2 and subsequently exposed to a range of low temperatures (cold shock) in order to model the dose-response surface (using survival as toxicity parameter). The data fitted a multiplicative model well (R2=0.99), and there was a highly significant synergistic interaction between Hg and cold shock. Our results indicate that the assessment of the toxicity of Hg by traditional laboratory studies where test organisms are exposed to only one stress factor and otherwise optimal conditions, may well underestimate the impact of the pollutant on the survival of field populations if stressful climatic conditions prevail. This conclusion is likely to apply to many other species and possibly other toxic chemicals as well. We propose that the present and similar research is needed for improvement of the scientific basis for setting safety factors in sound risk assessment of polluting chemicals.