Species-specific isotope tracers to study the accumulation and biotransformation of mixtures of inorganic and methyl mercury by the microalga Chlamydomonas reinhardtii

摘要

The present study demonstrates that species-specific isotope tracing is an useful tool to precisely measure Hg accumulation and transformations capabilities of living organisms at concentrations naturally encountered in the environment. To that end, a phytoplanktonic green alga Chlamydomonas reinhardtii Dangeard (Chlamydomonadales, Chlorophyceae) was exposed to mixtures of ~(199)-isotopically enriched inorganic mercury (~(199)IHg) and of ~(201)-isotopically enriched monomethylmercury (~(201)CH_3Hg) at a concentration range between less than 1 pM to 4 nM. Additionally, one exposure concentration of both mercury species was also studied separately to evaluate possible interactive effects. No difference in the intracellular contents was observed for algae exposed to ~(199)IHg and ~(201)CH_3Hg alone or in their mixture, suggesting similar accumulation capacity for both species at the studied concentrations. Demethylation of ~(201)CH_3Hg was observed at the highest exposure concentrations, whereas no methylation was detected.