Seasonal effects on the outcome of reproduction tests with silver nanoparticles, silver nitrate and the Collembola Folsomia candida

Abstract

Background Toxicity of silver nanoparticles (AgNP) is increasingly studied due to a rise in application in various products. Various studies on AgNP toxicity with terrestrial and aquatic organisms confirmed their negative effects. In our previous experiments, strong variability was observed in the reproduction of Collembola in different seasons. To investigate the effects of silver nanoparticles (AgNP) on the reproduction of Collembola in different seasons, Folsomia candida were exposed to AgNP and silver nitrate (AgNO 3 ) at a concentration of 30 mg/kg dry soil for 28 days. The reproduction tests were repeated during different seasons throughout one year in order to assess if animals’ sensitivity varied with the season. Results Significantly lower reproduction was found in the control in winter with only 101 (± 7) juveniles per adult, compared to 126-158 individuals in other seasons. Strong toxic effects (inhibition of reproduction by up to 50%) were observed during summer, spring and autumn in both treatments. However, AgNP showed no toxic effects on the reproduction of F. candida in winter. The relative toxicity of both substances varied with the seasons: AgNP were more toxic than AgNO 3 in spring and summer, and less toxic in autumn and winter. Conclusion These findings indicate that seasonal effects on the reproduction of Folsomia candida are significant. Moreover, we demonstrated the reproductive toxicity of AgNP in soil at a much lower concentration than reported thus far. These effects can mainly be attributed to soil conditions, which raises concern whether these commonly used test substrates are really protective.