Mercury toxicity to terrestrial snails in a partial life cycle experiment

Despite growing concerns about the potential adverse effects of elevated mercury (Hg) concentrations in the terrestrial environment, only a few toxicity data are available for soil invertebrates. The chronic toxicity of inorganic Hg-Hg(II)--through food or soil contaminations was therefore assessed for the snail Cantareus aspersus, a well-recognized soil quality bioindicator. The 28-day EC50s (the concentrations causing 50% effect) for the snail growth were 600 and 5048 mg Hg kg(-1) for food and soil, respectively. A survey of growth over its entire duration (91 days) allowed to show that the effects took place rapidly after the beginning of exposure and persisted in the long term. Reproduction was also impaired, and we established 28-day EC50s for sexual maturation and fecundity of 831 and 339 mg Hg kg(-1), respectively, for food and 1719 and 53 mg Hg kg(-1), respectively, for soil. Total Hg analyses in snails exposed to contaminated matrices revealed important bioaccumulation capacities up to 2000 mg Hg kg(-1) viscera. Critical limits in internal Hg concentration of about 500 and 1000 mg Hg kg(-1) were determined as thresholds for the induction of growth toxicity through food and soil exposure, respectively. These different values underlined differences in the uptake and toxicological dynamics of Hg according to its bioavailability in the source of exposure.