The effect of copper on the settlement success of larvae from the scleractinian coral Acropora tenuis

This study examined the effect of copper on the settlement success of planula larvae of the reef-building coral Acropora tenuis during 1994 and 1996 at Magnetic Island, Great Barrier Reef. Copper concentrations of 2, 10, 20 mug I-l did not inhibit larval settlement after 48-h exposure. However, copper concentrations of 42 mug l(-1) and 81 pg l(-1) significantly reduced settlement success of A. tenuis larvae after 48-h exposure compared with controls using normal seawater. At 200 mug l(-1) copper, all larvae died. EC50 values for the effect of copper on A. tenuis larval settlement were calculated from the 1996 results using measured copper concentrations. The 48-h EC50 was 35 mug l(-1) with an upper and lower 95% confidence limit of 37 mug l(-1) and 32 mug l(-1), respectively. The 48-h NOEC value for both experiments was 20 mug l(-1) copper. These experiments provide some of the first data on sub-lethal effects of trace metals on tropical marine organisms, and demonstrate that relatively low copper concentrations impair or inhibit settlement of coral larvae. (C) 2000 Elsevier Science Ltd. All rights reserved.