• Gissi, Francesca
• Garman, Emily
• Peters, Adam
• Smith, Ross
• Leung, Kenny
• Merrington, Graham
• Schlekat, Chris

Abstract

Tropical Southeast Asia and Melanesia (SEAM) represents an increasing source of nickel to global markets.Refined ecological risk assessment (ERA) are critical for sustainably managing Ni extraction and use; historically, few data were available to perform robust ERAs in tropical systems like SEAM.An initiative was launched in 2014 to obtain exposure and effects data needed for refined ERA.Exposure data were solicited from regional networks.Examination of tropical nickel effects data began by performing critical literature reviews and identifying key taxa for which data were lacking.Targeted ecotoxicity testing followed.Once sufficient data were collected, tropical nickel toxicity data were compared with temperate data, to determine the feasibility of combining the toxicity datasets to provide robust HC5s.Insufficient high quality exposure data were available to characterize the SEAM region.Available data indicate that freshwater systems of SEAM exhibit relatively high pH (7 to 8), and low calcium and dissolved organic carbon (DOC) concentrations (15 to 50 mg Ca/L; 1 to 3 mg DOC/L), representing high nickel bioavailability scenarios.Few data were found to characterize sediment and soil bioavailability conditions.Critical reviews of existing tropical chronic ecotoxicity data revealed gaps for marine and freshwater pelagic systems, and no high quality data for benthic systems.To this end, testing was performed on a range of marine organisms.Test organisms were selected based on their roles in critical tropical ecosystems, e.g., coral reefs, and on documented sensitivity of related organisms in temperate systems, e.g., gastropods and crustacea.Testing of juvenile and adult coral species, and their microbiomes, showed corals to be relatively insensitive to nickel.Comparisons between tropical and temperate toxicity datasets generally suggest that Ni sensitivities are similar for freshwater and marine systems, supporting the use of combined datasets for risk assessment purposes.No data for certain keystone species, e.g., amphidromous organisms, are available, and ERAs focusing on these species require specific approaches. Future Ni ERAs in the SEAM region can use the marine and freshwater toxicity databases to derive effects thresholds with high confidence.However, it is recommended that exposure data be collected on a site-specific basis.

Topics

• impedance spectroscopy
• Carbon
• nickel
• extraction
• Calcium
• toxicity