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3847520 
Journal Article 
The acute toxicity of major ion salts to Ceriodaphnia dubia: I. influence of background water chemistry 
Mount, DR; Erickson, RJ; Highland, TL; Hockett, JR; Hoff, DJ; Jenson, CT; Norberg-King, TJ; Peterson, KN; Polaske, ZM; Wisniewski, S 
2016 
Yes 
Environmental Toxicology and Chemistry
ISSN: 0730-7268
EISSN: 1552-8618 
35 
12 
3039-3057 
English 
27167636 
WOS:000391031400017 
The ions Na(+) , K(+) , Ca(2+) , Mg(2+) , Cl(-) , SO4(2-) , and HCO3(-) /CO3(2-) (referred to in the present study as "major ions") are present in all freshwaters and physiologically required by aquatic organisms but can increase to harmful levels from a variety of anthropogenic activities. It is also known that the toxicities of major ion salts can vary depending on the concentrations of other ions, and understanding these relationships is key to establishing appropriate environmental limits. The authors present a series of experiments with Ceriodaphnia dubia to evaluate the acute toxicity of 12 major ion salts and to determine how toxicity of these salts varies as a function of background water chemistry. All salts except CaSO4 and CaCO3 were acutely toxic below saturation, with the lowest median lethal concentrations found for K salts. All 10 salts that showed toxicity also showed some degree of reduced toxicity as the ionic content of the background water increased. Experiments that independently varied Ca:Mg ratio, Na:K ratio, Cl:SO4 ratio, and alkalinity/pH demonstrated that Ca concentration was the primary factor influencing the toxicities of Na and Mg salts, whereas the toxicities of K salts were primarily influenced by the concentration of Na. These experiments also indicated multiple mechanisms of toxicity and suggested important aspects of dosimetry; the toxicities of K, Mg, and Ca salts were best related to the chemical activity of the cation, whereas the toxicities of Na salts also reflected an influence of the anions and were well correlated with osmolarity. Understanding these relationships between major ion toxicity and background water chemistry should aid in the development of sensible risk-assessments and regulatory standards. Environ Toxicol Chem 2016;35:3039-3057. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.