LAUSR

The geographical shift of nickel mining to small island countries of the Southeast Asia and Melanesia region has produced a need to assess the environmental risk associated with increased sediment nickel exposure to benthic estuarine/marine biota. Chemical measurements of nickel concentration and potential bioavailability, including the use of diffusive gradients in thin films (DGT), were compared to effects on 10-d reproduction of the epibenthic estuarine/marine amphipod (Melita plumulosa) in nickel-spiked sediments and field-contaminated sediments with different characteristics. The 10% effect concentrations for amphipod reproduction (EC10) ranged from 280 to 690 mg/kg total recoverable nickel, 110 to 380 mg/kg dilute-acid extractable nickel, and 34 to 87 μg Ni/m2 /h DGT-labile nickel flux. Nickel bioavailability was lower in sediments with greater total organic carbon, clay content, and percentage of fine particles. DGT-labile nickel flux measurements at the sediment-water interface integrated exposure to nickel from pore water, overlying water and ingested sediment exposure pathways, and were found to have the strongest relationship with the biological response. At most, there was a 29% reduction in 10-d M. plumulosa reproduction relative to the control when exposed to nickel from field-contaminated sediments collected from nickel laterite mining regions of New Caledonia. DGT can be used as a complementary tool to measure the bioavailability of nickel in estuarine/marine sediments, especially sediments that are in nickel laterite mining regions where there are no or few toxicity data available for determining biological effects on local species. Based on the combined dataset of the three nickel-spiked sediments a DGT-labile nickel 10% effect concentration threshold of 50 (30 - 69) μg Ni/m2 /h was determined. This article is protected by copyright. All rights reserved.