Science for Decision Making on Uranium Mining in Arizona

Uranium bioaccumulation in aquatic invertebrates: A comparative study of spring-fed creeks in the Grand Canyon region

Regional Studies

In the Grand Canyon region, uranium (U) deposits occur in breccia pipes that extend vertically through sedimentary formations. Because the U deposita may be in contact with perched groundwater, U and other metals can travel from the breccia pipes to springs located along canyon walls forming streams that flow either intermittently or year round. The type and amount of salts and metals in the spring waters can provide information on the groundwater system and its interactions with both undisturbed and mined U deposits1, but little is known about U exposure to organisms inhabiting those steams. Although exposure occurs from contact with contaminated water as well as from ingestion of contaminated food, U bioaccumulation processes are understudied, especially in aquatic insects, thus limiting assessments of risk.

This project is studying uranium and associated trace element bioaccumulation in aquatic insects across a gradient of dissolved U concentrations occurring in spring outflow pools and creeks along the south rim of Grand Canyon National Park and adjacent watersheds located within federal lands. The data provide site-specific information on U and other metals that normally occur at low concentrations in the environment in surface water, sediment, aquatic insects, and in the material attached to submerged rocks and plants, a dietary exposure pathway for primary consumers2. Aquatic insects are targeted in this study because they represent a key step in the transfer of metals through aquatic food webs and are often ubiquitous in springs in the Grand Canyon region. Field data is also used along with laboratory derived data3,4 to predict U bioaccumulation in aquatic insects4 inhabiting the Grand Canyon region. Recent modeling results indicate that U accumulation is limited in baetid mayflies endemic to Grand Canyon region, despite sometimes elevated U concentrations, due to a combination of factors including low concentrations of bioavailable dissolved U species, slow U uptake rates from food, and fast U elimination4.


  • Describe the occurrence of U and co-occurring elements in environmental media (water and sediment) and biota (macroinvertebrates and periphyton) from creeks along the South Rim of Grand Canyon National Park and adjacent federal lands.

  • Determine whether relationships exist between U concentrations in environmental media and biota, and if any, identify underlying geochemical and physiological factors affecting such associations.

  • Use field data to refine and test U bioaccumulation models derived from laboratory studies conducted to characterize biogeochemical processes controlling bioaccumulation and toxicity.

  • Test the feasibility of generalizing model parameters derived using proxy species to species endemic to the Grand Canyon region.



Specific Tasks

Task 17: Determine biological effects of uranium + trace element mixtures


1 Beisner, K.R., Tillman, F.D., Anderson, J.R., Antweiler, R.C., and Bills, D.J., 2017, Geochemical characterization of groundwater discharging from springs north of the Grand Canyon, Arizona, 2009–2016: U.S. Geological Survey Scientific Investigations Report 2017–5068, 58 p.,

2 Fuller, C.C., Cain, D.J., Croteau, M-N., Barasch, D.A., Beisner, K.R., Stoliker, D.L., Schenk, E.R., 2018, Biogeochemical data of water, sediments, periphyton, and macroinvertebrates collected from springs in and near Grand Canyon National Park, Arizona (ver. 2.0, December 2019): U.S. Geological Survey data release,

3 Croteau, M.-M., Fuller, C.C., Cain D.J., Campbell, K.M., and Aiken, G., 2016, Biogeochemical controls of uranium bioavailability from the dissolved phase in natural waters: Environ. Sci. Tech. 50, 8120-8127.

4 Henry, B.L., Croteau, M.-N., Walters, D.M., Miller, J.L., Cain, D.J., Fuller, C.C. 2020. Uranium bioaccumulation dynamics in the mayfly Neocloeon triangulifer and application to site-specific prediction. Environ. Sci. Tech.

Principal Investigators

Daniel Cain
Biologist (Emeritus)
Earth System Processes Division, Water Mission Area

Marie-Noele Croteau
Research Biologist
Earth System Processes Division, Water Mission Area

Christopher Fuller
Hydrologist (Emeritus)
Earth System Processes Division, Water Mission Area

Kate Campbell-Hay
Research Chemist
Geology, Geophysics, and Geochemistry Science Center

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