The sensitivity of embryos and larvae of the crown-of-thorns sea star to copper and zinc: with respect to conditions experienced on the Great Barrier Reef and water quality guidelines

Our understanding of the ecotoxicology for tropical marine species is limited. We investigated the impacts of copper (0.1-6 µg/L) and zinc (2.5-45 µg/L) on development of the crown-of-thorns sea star (COTS) (Acanthaster sp.) with respect to lethal concentration (LC) and effective concentration (EC) for inhibition of larval swimming and in context with concentrations reported for the Great Barrier Reef (GBR) and the Australia and New Zealand Water Quality Guidelines (WQG). For embryos, copper caused 100 % mortality by 24 h and zinc arrested development by 36 h. The LC50s for bipinnaria for copper at 24 and 48 h were 0.67 and 0.54 µg/L and for zinc were 52.36 and 27.01 µg/L, respectively. For brachiolaria, these were 2.82 and 0.85 µg/L and 28.89 and 22 µg/L, respectively. For larval swimming the EC50 for copper was 0.35 µg/L and 0.66 µg/L in bipinnaria and brachiolaria, respectively. Larvae placed in copper (0.1-0.2 µg/L) recovered their swimming ability. Bipinnaria were resistant to zinc, EC50 of 28.89 µg/L for swimming, while for brachiolaria this was 7.18 µg/L. Acanthaster development was sensitive to copper and zinc at levels reported for nearshore GBR waters. This may contribute to the general absence of COTS on inshore reefs. Our data showed that the 95 % species protection for copper and zinc (1.3 µg/L and 15 µg/L, respectively) are not suitable for COTS development. This is likely to apply to many other species with similar planktonic larvae in GBR waters. This study will contribute to development of WQG for tropical marine waters.