The influence of soil moisture content on the bioavailability and toxicity of cadmium for Folsomia candida Willem (Collembola: Isotomidae)

For Collembola living in the upper soil and litter layers, soil moisture is a primary factor for survival. In addition, a shortage or surplus of moisture might interact with other stress factors, such as persistent pollutants. The aim of this study therefore was to investigate the response of the collembolan species Folsomia candida to cadmium at different soil moisture contents. Tests were performed in an artificial soil substrate at soil moisture levels of 25, 35, 45, and 55%, corresponding with 74, 103, 132, and 162% of field capacity, respectively. Cadmium sorption to the soils, estimated from water-soluble concentrations, was not significantly affected by soil moisture content. Significant effects of soil moisture content were found for the toxicity of cadmium on body weight of F. candida after 4 and 6 weeks. EC(50)s did, however, not differ by more than a factor of 2, Reproduction in the controls was strongly affected by soil moisture content, but EC(50)s for the effect of cadmium on reproduction did not differ for the different moisture levels. Cadmium concentrations in the animals were not significantly affected by soil moisture content. From this study it can be concluded that, within the range chosen, soil moisture content does not have a great influence on the bioavailability and toxicity of cadmium for the collembolan F. candida. (C) 1997 Academic Press.