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Last modified
8/11/2009 11:32:58 AM
Creation date
8/10/2009 5:10:24 PM
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UCREFRP
UCREFRP Catalog Number
9696
Author
Korte, N.E.
Title
Selenium poisoning of wildlife and western agriculture
USFW Year
2000.
USFW - Doc Type
cause and effect.
Copyright Material
NO
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notes that the relationship between the whole-body concentration of selenium and the prevalence <br />of teratogenic deformities in fish is exponential, such that relatively small changes in selenium <br />can cause large changes in the incidence of teratogenesis. <br />As noted above, with respect to concentrations in water, one researcher reports toxic effects on <br />bluegill at slightly more than 5 gg/L whereas other research shows no effect with razorback <br />suckers at 15 gg/L. Similarly, Crane et al. (1992) report that approximately 50% of a yellow <br />perch population disappeared during a 550-d pond experiment with a selenium concentration of <br />25 gg/L. Reproduction also was diminished at this concentration, but no obvious effects were <br />observed at 10 gg/L. <br />It is generally believed that food chain concentrations, rather than water concentrations, are a <br />better predictor of selenium toxicity. The data from the Uncompahgre Project area support this <br />contention, because several locations where selenium was elevated in fish had no detectable <br />selenium in the water (Butler et al. 1996). <br />A study by Hamilton et al. (1996) with razorback suckers demonstrates the difficulty in <br />developing unequivocal selenium criteria for protection of the endangered species. The study <br />was designed to obtain a dose-response curve, but instead there was 100% mortality, and the <br />median time to death was actually longer from the high selenium locations. The investigators <br />suggest that synergistic and antagonistic effects with other inorganics explain these observations, <br />but no studies were done to identify these effects. <br />Hamilton and Buhl (1996) discuss the difficulty of interpreting a study such as theirs by citing <br />another project with larval bluegill that had unexpected results (Coyle et al. 1993). The latter <br />study concluded that the fish died of starvation. However, Hamilton et al. (1996) state, "Because <br />high survival of larval fish [it was > 90%] fed brine shrimp nauplii during typical fish culture <br />operations had been observed, and brine shrimp can contain as much as 2.7 ug/g Se, this <br />concentration in aquatic invertebrates, by itself and in the absence of other biological, chemical, <br />or physical stressors, is probably not sufficient to cause adverse effects in larval fish. This <br />suggests that in the present investigation the adverse effects observed in studies 2, 3, and 4 in <br />larvae-fed food organisms from S 1 (selenium cone of 2.3 and 2.5 ug/g) or S4 (selenium cone of <br />2.4 ug/g) may not have been due to selenium alone but rather to the mixture of inorganics, <br />including Se, in the food organisms or S 1 water. Adverse effects observed. in the other treatments <br />and in fish fed food organisms from S 1 and S4 that contained 3.5 ug/g or more of selenium <br />probably due primarily to Se." These conclusions are based on research that indicates that 4 ug/g <br />of selenium in food will have toxic effects on fish, regardless of the species (Lemly 1993b). The <br />latter study noted. that 3 ug/g was a toxic threshold for fish species. The implications of these <br />interpretations, however, are significant because the final conclusion was that razorbacks are as <br />susceptible as rainbow trout, Chinook salmon, and bluegill, which are the most sensitive fish <br />species (Hamilton et al. 1996). <br />The only inorganic implicated, besides selenium in the latter study, was vanadium, which was <br />also present in zooplankton at concentrations believed to be toxic. Hamilton et al. (1996) quote <br />Hilton and Bettger (1988) who "concluded that dietary vanadium was at least as toxic, if not more <br />toxic, than dietary selenium." Another possible factor is reported by Saiki et al. (1993) who <br />attributes adverse effects at Kesterson to high concentrations of major ions in atypical ratios and <br />high concentrations of sulfate.
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