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

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.

[1]  D. A. Holdway.  Uranium toxicity to two species of Australian tropical fish , 1992 .

[2]  P L Brown,et al.  Valve movement responses of Velesunio angasi (Bivalvia: Hyriidae) to manganese and uranium: an exception to the free ion activity model. , 2000, Aquatic toxicology.

[3]  Rajeev Kapila,et al.  Annual Report 2007-2008 , 2008 .

[4]  B. Noller.  Non-radiological contaminants from uranium mining and milling at Ranger, Jabiru, Northern Territory, Australia , 1991, Environmental monitoring and assessment.

[5]  R. Gilbin,et al.  The effects of waterborne uranium on the hatching success, development, and survival of early life stages of zebrafish (Danio rerio). , 2008, Aquatic toxicology.

[6]  S. Markich,et al.  Chronic toxicity of uranium to a tropical green alga (Chlorella sp.) in natural waters and the influence of dissolved organic carbon. , 2005, Aquatic toxicology.

[7]  C L Humphrey,et al.  Mining in the Alligator Rivers Region, northern Australia: assessing potential and actual effects on ecosystem and human health. , 2002, Toxicology.

[8]  C. Finlayson,et al.  Assessment and monitoring of coastal change in the Alligator Rivers Region, northern Australia , 2000 .

[9]  C. Fortin,et al.  Metal‐phytoplankton interactions: Modeling the effect of competing ions (H+, Ca2+, and Mg2+) on uranium uptake , 2007, Environmental toxicology and chemistry.

[10]  P. Parrish,et al.  Early life stage toxicity tests with a saltwater fish: effects of eight chemicals on survival growth, and development of sheepshead minnows (Cyprinodon variegatus). , 1981, Journal of toxicology and environmental health.

[11]  K. Liber,et al.  Chronic Uranium Toxicity to White Sucker Fry (Catostomus commersoni) , 2004, Bulletin of environmental contamination and toxicology.

[12]  Franklin,et al.  pH-dependent toxicity of copper and uranium to a tropical freshwater alga (Chlorella sp.). , 2000, Aquatic toxicology.

[13]  J. H. Zar,et al.  Biostatistical Analysis (5th Edition) , 1984 .

[14]  D. Holdway.  Uranium mining in relation to toxicological impacts on inland waters , 1992, Ecotoxicology.

[15]  S. Barillet,et al.  Bioaccumulation, oxidative stress, and neurotoxicity in Danio rerio exposed to different isotopic compositions of uranium , 2007, Environmental toxicology and chemistry.

[16]  V. Camilleri,et al.  Changes in oxidative stress parameters in fish as response to direct uranium exposure , 2005 .

[17]  S. Markich.  Uranium Speciation and Bioavailability in Aquatic Systems: An Overview , 2002, TheScientificWorldJournal.

[18]  David R. Fox,et al.  Statistical Issues in Ecological Risk Assessment , 2006 .