The Effect of Copper, Zinc and Cadmium on Fertilization Success of Gametes from Scleractinian Reef Corals

Fertilization success of gametes from the scleractinian coral Goniastrea aspera was used to determine toxic effects of the trace metals copper, zinc and cadmium. Spawned eggs and sperm were collected from adult colonies of G. aspera and dosed separately with different concentrations of copper, zinc or cadmium, with normal seawater used as controls. The eggs and sperm were then combined to allow fertilization to occur. After 5 h development time, the number of fertilized and developing embryos and unfertilized eggs were counted and recorded to determine percentage fertilization. Copper was the most toxic metal, whereas cadmium and zinc did not affect fertilization success at the concentrations tested. High fertilization rates of 91% ± 3.2% and 93% ± 4.0% were recorded in the copper controls and in 2 μg/l of copper, respectively. However, fertilization success was significantly reduced to 41% ± 7.1% at 20 μg/l of copper, and <1% fertilization occurred at 200 μg/l of copper. In contrast, high fertilization rates were recorded in controls and in all concentrations of cadmium up to 200 μg/l, and in all concentrations of zinc up to 500 μg/l. Additional work on gametes from the reef coral Oxypora lacera showed no decrease in fertilization success up to 1000 μg/l of cadmium. These data are the first to show that relatively low concentrations of copper significantly affect fertilization rates of spawned gametes of reef corals from the Great Barrier Reef.