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Species-specific toxicity of major ion salts 2: Hyalella azteca, Lumbriculus variegatus, and Chironomus tentans
Citation:
Norberg-King, T., R. Erickson, B. Forsman, T. Highland, R. Hockett, C. Jenson, AND Dave Mount. Species-specific toxicity of major ion salts 2: Hyalella azteca, Lumbriculus variegatus, and Chironomus tentans. SETAC North America, Minneapolis, MN, November 12 - 16, 2017.
Impact/Purpose:
Surface waters can become enriched with major ions Adverse effects from increased concentrations of major geochemical ions (Na, K, Ca, Mg, Cl, SO4, HCO3) to aquatic organisms have been demonstrated or implied in many settings. Appropriate assessment and management of ion enrichment requires and understanding of how these ions affect aquatic organisms. This presentation provides an overview of the acute toxicity of ion mixtures to several aquatic species, comparing and contrasting their responses, and exploring how the differences and similarities might influence attempts to assess potential risks to aquatic communities.
Description:
Elevated major ion concentrations (Na, K, Ca, Mg, Cl, SO4, HCO3) have been recognized as a cause of surface water impairment and the toxicity of these major ions has been shown to be dependent on the specific ion composition of the water. A long-term research project was initiated at the U.S. EPA Mid-Continent Ecology Division to develop models that predict the toxicity of combinations of major ions. Research efforts initially focused on characterizing the toxicity of major ions and salt mixtures to Ceriodaphnia dubia. Subsequently, tests have been conducted with additional species with the goal of expanding the models to be more inclusive so that they can be better used to estimate risk in aquatic environments. This poster presents the results of acute toxicity tests conducted with three additional species: amphipods (Hyalella azteca), oligochaetes (Lumbriculus variegatus), and midges (Chironomus tentans). Over 200 acute toxicity tests were conducted with these species to determine: 1) the effect of the ion composition of background (dilution) water on the toxicity of salts and 2) the toxicity of different salt mixtures. Midges and L. variegatus are less sensitive to major ion salts than are C. dubia. Amphipods are more sensitive to some salts (e.g., MgSO4 and Na2SO4), but less sensitive than C. dubia to others (e.g., NaCl and CaCl2). There are also some notable qualitative differences in their response to mixtures. For example, while osmolarity is a good predictor of toxicity to C. dubia, Na2SO4 is more toxic to amphipods than can be accounted for by osmolarity. Differences in response suggest differences in toxic mechanism among the species.