R6 PM Bioavailability
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in 324-326

(WOR-1117-648482) Effects of water chemistry on nickel biouptake by the green alga, Chlamydomonas reinhardtii.

Worms, I¹, Wilkinson, K¹, ¹ Analytical and Biophysical Environmental Chemistry (CABE), Geneva, Switzerland

ABSTRACT- It is well known that the bioavailability of dissolved trace metals depends on many physico-chemical parameters including the temperature, pH, ionic strength of the water, etc.... Among other important parameters, the presence of ligands and major cations (Ca²⁺, Mg²⁺) has an important influence on biological responses to trace metals. Analytical chemistry has provided some responses, especially concerning the speciation of these pollutants in natural aquatic systems, but no general tool is available to evaluate trace metal bioavailability to aquatic organisms. Furthermore, no clear (fundamental) response to the question –what species in the media is controlling the biouptake process– has been proposed thus far. Based on the assumption that biological effects occurs when metals interact with intracellular components, we have determined short-term internalisation fluxes (J_int, mol cm^-2 s^-1 ) as an indicator of acute toxicity. The work demonstrates that Ni bioaccumulation is a steady-state process that can be best predicted by measuring equilibrium species of Ni in solution and by taking into account the quantitative interaction of competing ions for metal transport sites. In addition to providing greater insight into the mechanisms controlling the bioavailability of nickel to Chlamydomonas reinhardtii, the results allowed us to conclude that nickel biouptake was best predicted on the basis of the free ion activity (FIAM) or biotic ligand (BLM) models.

Key words: bioavailability, metal complexes, speciation, competition