title: Uranium toxicity and speciation during chronic exposure to the tropical freshwater fish, Mogurnda mogurnda.
abstract: The effects of chronic uranium (U) exposure on larval Northern trout gudgeon, Mogurnda mogurnda, were assessed in two experiments using a newly-developed 28d 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 2090microgL(-1) and 1070microgL(-1), respectively. Larval growth IC10s for Tests 1 and 2 were 860microgL(-1) and 660microgL(-1) (dry weight), and 1160microgL(-1) and 850microgL(-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 (4.2mgL(-1)) compared to Test 1 (2.1mgL(-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 13.7microgL(-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.
authors.affiliation: Ecotoxicology Program, Environmental Research Institute of the Supervising Scientist, GPO Box 461, Darwin, Northern Territory 0801, Australia.
authors.forename: K L
authors.initials: KL
authors.lastname: Cheng
authors.forename: A C
authors.initials: AC
authors.lastname: Hogan
authors.forename: D L
authors.initials: DL
authors.lastname: Parry
authors.forename: S J
authors.initials: SJ
authors.lastname: Markich
authors.forename: A J
authors.initials: AJ
authors.lastname: Harford
authors.forename: R A
authors.initials: RA
authors.lastname: van Dam
mesh_terms: D000818:Animals; D004781:Environmental Exposure; D006863:Hydrogen-Ion Concentration; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D010473:Perciformes / Q000254:growth & development / Q000378:metabolism*; D013997:Time Factors; D014501:Uranium / Q000633:toxicity*; D014875:Water Pollutants, Radioactive / Q000633:toxicity*
chemical_list: D014875:Water Pollutants, Radioactive; D014501:Uranium