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(328) Bioavailability of lipophilic metal complexes to Vibrio fischeri and Selenastrum capricornutum. Gilbin, Rodolphe1,2, Pardos, Michel2, Guéguen, Céline2, Gomez, Elena1, Casellas, Claude1, 1 2 ABSTRACT- Bioavailability of metals for microorganisms is generally governed by the free-ion activity in aquatic environments. Positively charged ions are known to be actively transported across the membrane. Complexes are considered as non-bioavailable (inert complexes) if they do not release metal ions (labile complexes). Some stable, lipophilic metal complexes (LMCs) can occur in the environment, especially in multi-contaminated environments, and increase the bioavailability of metals by passive diffusion across microorganism's membranes. The aim of this study was to assess the effect of lipophilic metal complexes vs. free-ion on a bacteria (Vibrio fischeri) and a unicellular algae (Selenastrum capricornutum). Experiments were carried out with divalent metals (Cu, Zn, Cd, Pb) and characterised lipophilic ligands (oxine, diethyl-dithiocarbamate). Results showed differences in bioavailability between free-ion and LMCs, i.e. increased toxicity (EC50) and faster toxicity kinetics of LMCs. These results will be related to the chemical speciation of each metal, as calculated with MINEQL model. Key words: metal bioavailability, lipophilic metal complexes, bioassays, speciation |
