The effects of metals of emerging concern on the fertilization success of gametes of the tropical scleractinian coral Platygyra daedalea

The demand for nickel and cobalt as important commodities has increased significantly over the past decade and a decline in the global nickel sulphide reserves has resulted in a shift toward the exploitation of the less favourable nickel laterite ores. These deposits, which are found associated with cobalt, are located predominantly in the tropical regions of the world where there is limited understanding of the toxicities of their extracted products and wastes. This study investigated the effects of nickel, cobalt and combinations of nickel and cobalt on the fertilization success of the common and widespread scleractinian coral Platygyra daedalea. We also present the first assessment of the effect of copper on fertilization success of this species. The EC₅₀ value for copper was 33 μg L⁻¹ (95% confidence limits: 30–37 μg L⁻¹) and is consistent with published values for other coral species. Our results provide the first EC₅₀ value for the effect of nickel on fertilization success in a scleractinian coral, with an estimated value of 1420 μg L⁻¹ (95% confidence limits: 1160–1780 μg L⁻¹). Concentrations of cobalt as high as 2500 μg L⁻¹ did not significantly reduce fertilization success nor did combinations of nickel (500 μg L⁻¹) and cobalt (up to 1000 μg L⁻¹). These are important findings given the emerging nickel-cobalt mining industry in the tropics and provide much needed toxicity data regarding the early-life histories of ecologically relevant tropical marine species.