Toxicity of Binary Metal Mixtures to the Tropical Ostracod Strandesia Trispinosa

The ecotoxicity of metals is generally assessed individually, in part because current knowledge does not allow for the accurate prediction of the toxicity of metal mixtures to aquatic organisms. The objective of this study was to investigate the toxic effects of binary combinations of metal salts (copper sulphate—CuSO 4 , cadmium chloride—CdCl 2 , mercury chloride—HgCl 2 and manganese sulphate—MnSO 4 ) on the tropical ostracod Strandesia trispinosa through acute toxicity tests. To this end, ostracods were exposed to each individual metal salt as well as to their combinations by applying a full factorial design. The model that best explained the effects of the mixtures CuSO 4 x CdCl 2 , CuSO 4 x HgCl 2 and CuSO 4 x MnSO 4 on the survival of S . trispinosa was Concentration Addition, whereas this was Independent Action for the CdCl 2 x HgCl 2 mixture. The observed synergistic interactions are likely to result in unacceptable risks to aquatic ecosystems under real field conditions. This is especially the case if CuSO 4 predominates the metal mixture, as observed for its combination with mercury and manganese.