A comparison of dietary and aqueous uranium exposure routes in Atlantic salmon
Uranium is a naturally occurring radionuclide. Mining, road and tunnel construction in areas with alum shale can increase the uranium concentration in the environment by leaching of exposed bedrock. As of 2011, the Norwegian Pollution Act has mandated the inclusion of radionuclides in the assessment of acceptable concentration limits in the environment and has pressed the research community to understand the biological effects of natural radionuclides (e.g. uranium). Previous experiments with uranium have demonstrated uptake and toxicity of U towards aquatic organisms, including fish, directly from water exposures. In addition, field-based observations have shown that the magnitude of uranium concentrations in fish from similar lakes can vary significantly. One hypothesis is that the dietary uptake of uranium can play a significant contribution to the total concentration in fish. However, no information exists on the uptake, effects or biological half-life of uranium by diet. Such information can only be achieved in experiments with fish.
Atlantic salmon are ecologically and economically valuable in Norway and are considered one of the most sensitive fish species. For this reason, it is important to study the impacts of uranium on this species and determine potential risk. The purpose of this study is to compare the uptake, elimination, effects and biological half-life of uranium exposed to both dietary and aqueous exposure routes in juvenile Atlantic salmon. One novelty of this experiment is that salmon will be exposed to a live source (Daphnia magna) containing U, which is more environmentally realistic (mimicking real ecosystems) compared to typical food pellet diets. In addition, fish will be fed with food pellets to compare U transfer from different sources. The salmon will be exposed to pre-determined sub-lethal concentrations of uranium, which minimizes organism stress over the course of the 3 month study. If the uranium uptake reaches steady state earlier, the experimental period will be correspondingly shorter. The experiment should give information about transfer of uranium and will only give sub-lethal effects on most sensitive biomarkers with little stress to fish. According to guidelines for similar studies (OECD test no. 305), a total of 656 fish are required to conduct this experiment and coheres to the requirements for a complete bioaccumulation study within the statistical needs. The number of fish is a minimum to achieve the main aim of the experiment within guideline requirements and results will be used to develop uranium transfer models in fish.
Atlantic salmon are ecologically and economically valuable in Norway and are considered one of the most sensitive fish species. For this reason, it is important to study the impacts of uranium on this species and determine potential risk. The purpose of this study is to compare the uptake, elimination, effects and biological half-life of uranium exposed to both dietary and aqueous exposure routes in juvenile Atlantic salmon. One novelty of this experiment is that salmon will be exposed to a live source (Daphnia magna) containing U, which is more environmentally realistic (mimicking real ecosystems) compared to typical food pellet diets. In addition, fish will be fed with food pellets to compare U transfer from different sources. The salmon will be exposed to pre-determined sub-lethal concentrations of uranium, which minimizes organism stress over the course of the 3 month study. If the uranium uptake reaches steady state earlier, the experimental period will be correspondingly shorter. The experiment should give information about transfer of uranium and will only give sub-lethal effects on most sensitive biomarkers with little stress to fish. According to guidelines for similar studies (OECD test no. 305), a total of 656 fish are required to conduct this experiment and coheres to the requirements for a complete bioaccumulation study within the statistical needs. The number of fish is a minimum to achieve the main aim of the experiment within guideline requirements and results will be used to develop uranium transfer models in fish.