Uptake and toxicity of Cd, Cu and Pb mixtures in the isopod Asellus aquaticus from waterborne exposure

- Synergistic interactions of Cd and Pb mixtures on uptake and toxicity were observed.
- Effects of Cd and Pb mixtures on toxicity were related to increased Cd uptake.
- No mixture interactions between Cu and Cd or Pb were observed.

The present study evaluated interactions of waterborne Cd, Cu and Pb mixtures on metal uptake rates in the isopod Asellus aquaticus and related this to mixture effects on toxicity. Secondly, it was assessed whether observed mixture effects were better related to isopod body concentrations compared to exposure concentrations. Isopods were exposed for 10 days to single, binary and tertiary mixtures including five different concentrations of Cd (0.107 to 277 μg L− 1), Cu (3.35 to 2117 μg L− 1) and Pb (0.782 to 443 μg L− 1). Mortality was assessed every day while isopod body concentrations, growth (biomass) and energy reserves (glycogen, lipid and protein reserves) were assessed at the end of the experiment.Synergistic interactions of combined Cd and Pb exposure on Cd and Pb uptake as well as on growth rates and mortality rates were observed. Mixture effects of combined Cd and Pb exposure on toxicity endpoints were directly related to increased Cd uptake in the Cd + Pb treatment. No mixture interactions of Cu on Cd or Pb uptake (and vice versa), nor on toxicity endpoints were observed. All toxicity endpoints were related to body concentrations. However, mixture effects disappeared when growth and mortality rates were expressed on body concentrations instead of exposure concentrations.By combining information of mixture effects on metal uptake with mixture toxicity data, the present study provides more insight in the way metal mixtures interfere with aquatic organisms and how they can induce toxic effects.

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