where TTM is the predicted total toxicity of the mixture, Ci is the concentration of the compound and WQCi is the guideline for that compound. The mixture is considered as exceeding the WQC if TTM is greater than 1 (ANZECC 2000). This criterion assumes simple additivity of the toxic effect of the mixture and does not account for potential synergism.
The aims of this study were to provide 1) a first measure of metal toxicity in two important coastal NZ species, 2) a comparison of metal toxicity with the current WQC to assess its validity using local species, and 3) an evaluation of toxicity behaviour (e.g. synergistic, antagonistic) in simple metal mixtures. These aims were addressed with standard biotoxicity assays on H. iris and E. chloroticus embryo and larval stages.