John Wiley & Sons, Ltd.

Aluminium, Gallium and Molybdenum Toxicity to the Tropical Marine Microalga Isochrysis galbana

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There is a shortage of established chronic toxicity test methods for assessing the toxicity of contaminants to tropical marine organisms. We tested the suitability of the tropical microalga Isochrysis galbana for use in routine ecotoxicology and assessed the effects of 72‐h exposures to copper (Cu, a reference toxicant), aluminium (Al), gallium (Ga) and molybdenum (Mo), key metals of alumina refinery discharge, on the growth of I. galbana at three temperatures; 24, 28 and 31°C. The sensitivity of both Isochrysis galbana and the test method was validated by the response to Cu exposure, with an EC10 and EC50 of 2.5 μg/L and 18 μg/L respectively. The 10% and 50% effect concentrations (EC10 and EC50) for total Al at 28°C were 640 μg/L and 3045 μg/L respectively. The toxicity of both Cu and Al at 24°C and 31°C was similar to that at 28°C. There was no measurable toxicity from dissolved Ga exposures of up to 6000 μg/L nor exposures to dissolved Mo of up to 9500 μg/L. Solubility limits at 28°C for the dissolved fraction (<10 kDa) of Al, Ga and Mo were: ~650 μg/L Al, > 7000 μg/L Ga and >6000 μg/L Mo. In test solutions containing >650 μg/L total Al, dissolved and precipitated forms of Al were present with precipitated Al becoming more dominant as total Al increased. This test method proved suitable for routine ecotoxicology, with I. galbana showing sensitivity to Cu but Al, Ga and Mo exhibiting little to no toxicity to this species. This article is protected by copyright. All rights reserved

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