Effects of copper on the fertilization success of the soft coral Lobophytum compactum

This study provides the first information on the effects of various concentrations of copper on the fertilization success of gametes from the soft coral Lobophytum compactum. Two experiments were conducted to determine the effect of copper on fertilization success during the mass coral spawning in 2004 on the Great Barrier Reef (GBR). The results from the first experiment showed a surprising resistance to copper with control treatments showing 90% fertilization compared to 65% fertilization in measured copper concentrations up to 132 μg/L. Copper concentrations of 69 μg/L and higher resulted in significantly reduced fertilization success when compared to the controls. Copper doses were increased in experiment 2 and the EC50 value for copper effects on fertilization success was 261 μg/L (208-328 μg/L, 95% confidence limits). In this follow-up experiment, fertilization success was significantly lower than the controls after exposure to copper concentrations of 117 μg/L and above. The EC50 value reported here is much higher than those found in the literature on fertilization experiments conducted on hard coral gametes and also for the fertilization success of other marine organisms, including sea urchins, oysters and fish.