In Chapter 5, the toxicity of copper was evaluated in both normal and low salinity seawater, as metal discharge in coastal water is generally associated with freshwater(e.g. storm water or river plumes). Here I used embryos and larvae of E. chloroticus to characterise the effect of low salinity on copper toxicity with variable timing of exposure. In embryo/early pluteus assays, embryos were exposed for 72 h shortly after fertilisation. In larval assays, larvae were either exposed chronically to treatments or in a single pulse to better mimic realistic field conditions.