ABSTRACT
Short-term bioassays on marine invertebrate early life stages are a widely used method to evaluate toxicity of a single compound or mixed compounds. This study provides the first evaluation of toxicity of three major pollutants (copper, lead and zinc) on Evechinus chloroticus and Haliotis iris; two large benthic invertebrates species endemic to New Zealand. Larval development assays were conducted for 72 h with individual metals and their binary mixtures. All three metals significantly affected larval development of both species. Median effective concentrations (EC50)based on nominal concentrations were 5.4 μg/L Cu, 52.2 μg/L Pb, 27.7 μg/L Zn for E.chloroticus and 3.4 μg/L Cu, 775 μg/L Pb, 13.1 μg/L Zn for H. iris. ‘No observable effect concentrations’ (NOEC) based on larval size were lower than those based on larval development for lead but not for copper and zinc in E. chloroticus. None of the metals tested affected H. iris larval size. Effects of metal mixtures were analysed
using a toxic unit (TU) method. Cu + Zn had an antagonistic effect on E. chloroticus development. All other pairs were found to have a slightly less-than-additive or strictly additive effect. None of the interactions were strong, with sums of TU ranging from 1.00 to 1.85. Both species were extremely sensitive to copper and zinc with EC50 values near or above current NZ water quality criteria (WQC) and highlight the importance of obtaining toxicity data for species of special importance instead of relying exclusively on indicator species or international studies.