3.4.4 CONCLUSION
My results show that even a short pulse of copper during larval development may have long lasting effects, especially on settler growth and resistance to further stress.When larvae are vulnerable to a stressor throughout their whole larval development,as was the case here, adult populations close to the source of larval stress not only produce few recruits but also have a low chance of acquiring recruits dispersed from populations further from the stressor source (Shima et al. 2010). Therefore, transient larval exposure, as in a river plume, may have a strong impact on recruitment and local population persistence. Decreased resistance to further stress is of special importance as larvae exposed to pollution are likely to settle in a polluted area; this is especially the case for species with low dispersal. On the other hand, selective mortality after subsequent copper exposure might mitigate the impact at the population level, as only the fitter, faster growing juveniles would survive. Only the highest level of copper (10.4 μg/L) produced latent effects after a single exposure, but even very low level approaching ANZEEC water quality criterion (2.3 μg/L)produced a decreased resistance to further copper exposure. This study highlights the importance of evaluating long-term effect of toxicants, as no strong impact was seen until 8 d post-settlement.