Flowback and produced water (FPW) is an end-product of the hydraulic fracturing method of oil and gas extraction that is highly enriched in alkaline earth metals such as strontium (Sr). While Sr concentrations in FPW can exceed toxic thresholds for fish, the accompanying high concentrations of calcium (Ca) in FPW may ameliorate any toxicity. In this study, Sr bioaccumulation and molecular, biochemical, and physiological changes in ionoregulatory endpoints were investigated in rainbow trout (Oncorhynchus mykiss). Exposures were conducted over a 96-h period at Sr concentrations ranging from 1.7 to 1948 µM, with effects at the highest Sr exposure concentration also separately examined in waters of varying Ca concentration (10 to 958 µM). Plasma and gill Sr burdens increased as a function of increasing waterborne Sr, and accumulation increased further as water Ca concentrations were lowered. Despite this, there was no consistent, dose-dependent effect of Sr on plasma or gill Ca concentrations, although impacts on plasma and branchial sodium (Na) concentrations were observed. Waterborne Sr significantly inhibited branchial Ca²⁺-ATPase activity, albeit only at the highest tested Sr concentration (1948 µM). In exposure treatments where Sr was highly elevated and water Ca was reduced, the hepatic gene expression of Ca signaling receptors β-2 adrenergic receptor (Adrb2) and inositol-1,4,5-triphosphate receptor-2 (Itpr2) were inhibited, highlighting novel potential pathways of Sr toxicity in rainbow trout. Overall, these data indicate that water Ca has a strong effect on Sr bioavailability, but over an acute exposure period there is limited evidence for an effect of Sr on Ca homeostasis. Although Sr is elevated in effluents associated with the oil and gas industry, the co-occurrence of high Ca concentrations might protect freshwater fish against acute effects related to Sr exposure.

回流和采出水 (FPW) 是石油和天然气开采水力压裂方法的最终产品，富含锶 (Sr) 等碱土金属。虽然 FPW 中的 Sr 浓度可能超过鱼类的毒性阈值，但 FPW 中伴随的高浓度钙 (Ca) 可能会改善任何毒性。在这项研究中，研究了虹鳟鱼 ( Oncorhynchus mykiss ) 中 Sr 的生物积累和离子调节终点的分子、生化和生理变化。）。在 Sr 浓度范围为 1.7 到 1948 µM 的情况下，在 96 小时内进行了暴露，最高 Sr 暴露浓度的影响也在不同 Ca 浓度（10 到 958 µM）的水中单独检查。血浆和鳃 Sr 负荷随着水性 Sr 的增加而增加，随着水中 Ca 浓度的降低，积累进一步增加。尽管如此，尽管观察到对血浆和鳃钠 (Na) 浓度的影响，但 Sr 对血浆或鳃 Ca 浓度没有一致的剂量依赖性影响。水性锶显着抑制鳃Ca ²⁺-ATPase 活性，尽管仅在最高测试 Sr 浓度 (1948 µM) 下。在 Sr 高度升高和水 Ca 降低的暴露处理中，Ca 信号受体 β-2 肾上腺素能受体 (Adrb2) 和肌醇-1,4,5-三磷酸受体-2 (Itpr2) 的肝脏基因表达受到抑制，突出显示虹鳟鱼 Sr 毒性的新潜在途径。总体而言，这些数据表明水 Ca 对 Sr 的生物利用度有很强的影响，但在急性暴露期间，Sr 对 Ca 稳态的影响的证据有限。尽管 Sr 在与石油和天然气工业相关的废水中升高，但同时出现的高 Ca 浓度可能会保护淡水鱼免受与 Sr 暴露相关的急性影响。