TOXICITY OF NICKEL ORES TO MARINE ORGANISMS

Queensland Nickel proposes to import New Caledonian (Ballande) and Ind onesian (Gebe) nickel ores, one option being ship-to-barge transfer in Halifax Bay, North Queensland. Because small amounts of ore may be sp ilt during the unloading and transfer operations, it was important to investigate the potential impact of the spilt ore on the ecological he alth of the Bay. Long-term leaching of the ores with seawater showed t hat only nickel and chromium(VI) were released from the ores in suffic ient concentrations to cause toxicity to a range of marine organisms. The soluble fractions of nickel and chromium(VI) were released from th e ores within a few days. Nickel, chromium(VI) and the ore leachates s howed similar toxicity to the juvenile banana prawn Penaeus merguiensi s, the amphipod Allorchestes compressa and both temperate (22-degrees- C) and tropical (27-degrees-C) strains of the unicellular marine alga Nitzschia closterium. In a series of 30-day sub-chronic microcosm expe riments, juvenile leader prawns Penaeus monodon, polychaete worms Gale olaria caespitosa and the tropical gastropod Nerita chamaeleon were al l very resistant to the nickel ores, with mortality unaffected by 700 g ore per 50 1 seawater. The growth rate of the leader prawns was, how ever, lower than that of the controls. From these data, a conservative maximum safe concentration of the nickel ores in seawater is 0.1 g l- 1. The nickel ore was not highly toxic and if spilt in the quantities predicted, would not have a significant impact on the ecological healt h of the Bay.