Freshwater biota are at risk globally from increasing salinity, including increases from deicing salts in cold regions. A variety of metrics of toxicity are used when estimating the toxicity of substances and comparing the toxicity between substances. However, the implications of using different metrics are not widely appreciated. Using the mayfly Colobruscoides giganteus (Ephemeroptera: Colobruscoidea), we compare the toxicity of seven different salts where toxicity was estimated using two metrics: (1) the no-effect concentrations (NEC) and (2) the lethal concentrations for 10, 25 and 50% of the test populations (LC_x). The LC_x values were estimated using two different models, the classic log-logistic model and the newer toxicokinetic–toxicodynamic (TKTD) model. The NEC and both types of LC_x values were estimated using Bayesian statistics. We also compared the toxicity of two salts (NaCl and CaCl₂) for C. giganteus at water temperatures of 4 °C, 7 °C and 15 °C using the same metrics of toxicity. Our motivation for using a mayfly to assess salinity toxicity was because mayflies are generally salt sensitive, are ecologically important and are common in Australian (sub-)alpine streams. The temperature ranges were chosen to mimic winter, spring and summer water temperatures for Australian (sub-)alpine streams. Considering 144-h classical LC_x values, we found toxicity differed between various salts, i.e., the lowest 144-h LC₅₀ (8 mS/cm) for a salt used by a ski resort was half that of the highest 144-h LC₅₀ from artificial marine salts and CaCl₂ applied to roads (16 mS/cm). The analytical grade NaCl (as shown by 144-h LC₅₀ value at 7 °C) was substantially more toxic (7.3 mS/cm) compared to analytical grade CaCl₂ (12.5 mS/cm). Yet for NEC values, there were comparably fewer differences in toxicity between salts and none between the same salts at different temperatures. We conclude that LC_x values are better suited to compare the difference in toxicity between substances or between the same substance at different test temperatures, while NEC values are better suited to estimating concentrations of substances that have no effect to the test species and endpoint measured under laboratory conditions.

全球淡水生物群因盐度增加而面临风险，包括寒冷地区除冰盐的增加。在估算物质的毒性和比较物质之间的毒性时，会使用多种毒性指标。然而，使用不同指标的含义并未得到广泛认可。使用蜉蝣Colobruscoides giganteus (Ephemeroptera: Colobruscoidea)，我们比较了七种不同盐的毒性，其中毒性使用两个指标进行估计：(1) 无效应浓度 (NEC) 和 (2) 10、25 和50% 的测试人群 (LC _x )。信用证_x使用两种不同的模型估计值，经典对数逻辑模型和较新的毒代动力学-毒代动力学 (TKTD) 模型。使用贝叶斯统计估计NEC 和两种类型的 LC _x值。我们还使用相同的毒性指标比较了在 4 °C、7 °C 和 15 °C 的水温下两种盐（NaCl 和 CaCl ₂）对C. giganteus的毒性。我们使用蜉蝣来评估盐度毒性的动机是因为蜉蝣通常对盐敏感，在生态上很重要，并且在澳大利亚（亚）高山溪流中很常见。选择温度范围以模拟澳大利亚（亚）高山溪流的冬季、春季和夏季水温。考虑 144 小时经典 LC _x值，我们发现各种盐的毒性不同，即滑雪胜地使用的盐的最低 144 小时 LC ₅₀ (8 mS/cm) 是人工海盐和氯化钙最高 144 小时 LC _50的一半2适用于道路 (16 mS/cm)。_{与分析级 CaCl 2} (12.5 mS/ cm) 相比，分析级 NaCl (如 7 °C 下的 144 小时 LC ₅₀值所示) 的毒性 (7.3 mS/cm) 明显更高。然而，对于 NEC 值，盐之间的毒性差异相对较小，而在不同温度下相同的盐之间则没有。我们得出结论，LC _xNEC 值更适合比较物质之间或同一物质在不同测试温度下的毒性差异，而 NEC 值更适合估计在实验室条件下测量的对测试物种和终点没有影响的物质的浓度。