Acute and chronic toxicity of nickel on freshwater and marine tropical aquatic organisms

Water quality guidelines and ecological risk assessment of chemical substances like nickel (Ni) in tropical regions such as South East Asia and Melanesia are often based on temperate information as a result of fewer Ni ecotoxicity data available for tropical species. This leaves an unknown margin of uncertainty in the risk assessment in the tropics. In order to fill this data gap, this study was designed to conduct standard toxicity tests on Ni with two freshwater species (acute tests) and three marine species (acute and chronic tests) originated from tropical Hong Kong. All tests were carried out using measured concentrations of Ni with control mortality below 15%. The median lethal concentrations (LC₅₀s) were determined as 2520 (95% confidence interval: 2210, 2860) and 426 (351, 515) μg Ni L⁻¹ for the freshwater gastropods Pomacea lineata (48 h) and Sulcospira hainanensis (96 h), respectively, while 96 h LC₅₀s of 4300 (3610, 5090), 18,200 (6470, 51,200), 62,400 (56,800, 68,500), and 71,700 (68,200, 75,400) μg Ni L⁻¹ were derived for the marine copepod Tigriopus japonicus, the gastropod Monodonta labio, juvenile and adult of the marine fish Oryzias melastigma, respectively. The chronic effect concentration of 10% (EC₁₀) based on the intrinsic rate of increase of the population of T. japonicus was 29 (12, 69) μg Ni L⁻¹. In terms of growth inhibition, the chronic EC₁₀ for M. labio was 34 (17, 67) μg Ni L⁻¹. The results also indicated that T. japonicus in maturation stage (LC₁₀: 484 (349, 919) μg Ni L⁻¹) was less sensitive than its nauplii stage (LC₁₀: 44 (27, 72) μg Ni L⁻¹). This study represents an important addition of high-quality toxicity data to the tropical Ni toxicity database which can be used for future ecological risk assessment of Ni and derivation of its water quality guidelines in tropical regions.