Great Lakes Environmental Center (GLEC) conducted flow-through acute toxicity tests in support of ambient water quality criteria development for the U.S. Environmental Protection Agency (EPA). The objective of the work was to supply EPA with acute selenate and selenite toxicity data for Gammarus and Ceriodaphnia to update the toxicity database in support or ambient water quality criteria and sediment criteria development. Gammarus and C.dubia were exposed under flow-through conditions to measured concentrations of sodium selenite (Se+4) and sodium selenate (Se+6) in a flow-through system to determine the acute toxicity of both forms of selenium. Ultimately, the median lethal toxicant concentration (LC50) was estimated from the 96-hour acute toxicity tests. Results indicated that there was significant differences between the acute toxicity of selenite and selenate indicating that the ambient water quality criteria for selenium should be based on the specific form of selenium discharged or available to the aquatic organism.
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