Uranium toxicity and speciation during chronic exposure to the tropical freshwater fish, Mogurnda mogurnda

• Published in: Chemosphere (Oxford) 2010-04, Vol.79 (5), p.547-554
• Main Authors: Cheng, K.L., Hogan, A.C., Parry, D.L., Markich, S.J., Harford, A.J., van Dam, R.A.
• Format: Article
• Language: English
• Subjects: Air. Soil. Water. Waste. Feeding; Animals; Applied sciences; Biological and medical sciences; Carbon; Chronic toxicity; Environment. Living conditions; Environmental Exposure; Exact sciences and technology; Fish; Hydrogen-Ion Concentration; Larva - drug effects; Larva - metabolism; Mathematical models; Medical sciences; Mogurnda mogurnda; Perciformes - growth & development; Perciformes - metabolism; Pollution; Public health. Hygiene; Public health. Hygiene-occupational medicine; Speciation; Survival; Time Factors; Toxicity; Tropical; Uranium; Uranium - toxicity; Water Pollutants, Radioactive - toxicity; Water quality guideline
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2010.02.017

The effects of chronic uranium (U) exposure on larval Northern trout gudgeon, Mogurnda mogurnda, were assessed in two experiments using a newly-developed 28 d survival and growth toxicity test. Significant effects were observed in both tests, but toxicity was markedly higher in Test 2 than Test 1. The LC50s for Tests 1 and 2 were 2090 μg L −1 and 1070 μg L −1, respectively. Larval growth IC10s for Tests 1 and 2 were 860 μg L −1 and 660 μg L −1 (dry weight), and 1160 μg L −1 and 850 μg L −1 (length), respectively. Uranium speciation modelling showed that a lower pH in Test 2 (mean of 6.0) compared to Test 1 (mean of 6.7) resulted in a greater proportion of free uranyl ion ( UO 2 2 + ), the predominant bioavailable form of U. A higher dissolved organic carbon concentration (DOC) in Test 2 (4.2 mg L −1) compared to Test 1 (2.1 mg L −1) resulted in a higher proportion of U-DOC in Test 2, but this was insufficient to counter the effect of pH on the proportion of UO 2 2 + . The difference in U toxicity between the two tests could be explained by normalising for UO 2 2 + ; the concentrations of UO 2 2 + at the LC50s for Tests 1 and 2 were calculated to be 13.3 and 13.7 μg L −1, respectively. Finally, the results of this study, and comparisons with other studies suggest that U toxicity to M. mogurnda appears to be as much, if not more, a function of exposure water quality and feeding regime, as exposure duration.