Environmental Health - Toxic Substances Hydrology Program
… ecological risk assessment for a specific predator species must consider all three factors involved in toxicity:
Luoma and Presser, 2009
A new unified approach to evaluating the toxicity of selenium could help ecologists faced with varied and inconsistent approaches to assessing the toxicity of selenium in rivers, estuaries, and other water bodies. A team of U.S. Geological Survey (USGS) scientists proposed an ecosystem-scale model of the fate of selenium in the environment. The model quantifies how selenium is transferred from water and into predatory fish and birds through dietary uptake. The model integrates the chemistry of biological and geological systems and the physiological factors that control how various animals within food webs bioaccumulate selenium.
The approach shows that environmentally safe concentrations of selenium dissolved in water vary among ecosystems because the factors that affect whether selenium reaches toxic levels in fish and birds depends on the unique ecological and chemical conditions in each ecosystem. For example, the amount of selenium transferred within a local food web will differ depending on the species involved because different species bioaccumulate selenium at different rates and amounts. The unified approach is implemented in a computer model. The model provides a tool that ecologists, regulators, water resource managers, and other environmental professionals can use to:
The model is unique because it integrates:
Each trophic level (the placement of an organism within a food web or what an organism eats and what eats it) in the model is assigned a trophic transfer factor. These factors are different for each organism in the simulated food web. For example, a clam bioaccumulates selenium at a different rate than an insect, but both are prey for fish and birds. The model has been validated using 29 case studies. The development of the model is part of collaborative investigations with the U.S. Environmental Protection Agency and U.S. Fish and Wildlife Service.
Luoma, S.N., and Presser, T.S., 2009, Emerging opportunities in management of selenium contamination: Environmental Science & Technology, v. 43, no. 22, p. 8483-8487, doi:10.1021/es900828h.