EFFECTS OF EXPOSURE AND PREVIOUS EXPOSURE TO COPPER ON GROWTH OF VELIGER LARVAE AND SURVIVORSHIP OF MYTILUS-EDULIS JUVENILES

Exposure of Mytilus edulis L. (Mollusca: Bivalvia) to 8 ppb (ppb = mu g l(-1)) added copper during the veliger larval or post-larval (spat) stages has no significant effects on survivorship or shell growth. How ever, previous exposure to 8 ppb added copper during the embryo stage significantly increases veliger growth rate and decreases spat survivo rship in a population from the Menai Strait, Wales, UK, in which this level of copper causes a significant increase in embryo abnormality. N o such effects of pre-exposure are seen in a population from the Weste rschelde, The Netherlands, where 8 ppb added copper does not constitut e a stress on the embryo. These 'pre-incubation' (embryo exposure) eff ects far outweigh any direct influence of 8 ppb copper exposure during the later stages and have a substantial effect on estimates of the to xicity of copper over the life cycle of M. edulis.