2.4.1 COMPARISON WITH CURRENT WATER QUALITY CRITERIA
The 72 h-EC50s showed a decreasing order of toxicity for each metal as follows for both species: Cu > Zn > Pb. H. iris and E. chloroticus appeared to be highly sensitive to copper with EC50s being near, but above, WQC. Cu EC10 for H. iris was below WQC, suggesting that H. iris larvae could be notably affected if such a concentration ever occurs frequently in coastal waters (20% abnormal larvae at WQC level). This is of concern as, in New Zealand, copper has been found to be above WQC in urban effluents (Milne & Watts 2008, Neale 2009), marinas (Gadd & Cameron 2012) and, to a lesser extent, coastal water near agricultural effluent (Appendix A). While zinc
was less toxic than copper, WQC are higher for this metal and concentrations at this
level are likely to severely affect H. iris (55% abnormal larvae at WQC level) and
moderately affect E. chloroticus (25% abnormal larvae at WQC level). The EC50
value for H. iris was lower than WQC, indicating a potential failure of WQC to
protect this species in NZ. Lead was not a concern for either species, with both EC50s
and EC10s well above WQC.