The extensive utilization of Zinc Oxide nanoparticles (ZnO NPs) has garnered significant attention due to their detrimental impacts on ecosystem. Unfortunately, ecotoxicity of ZnO NPs in coastal waters with fluctuating salinity has been disregarded. This study mainly discussed the toxic effects of ZnO NPs on species inhabiting the transition zones between freshwater and brackish water, who are of great ecological and economic importance among fish. To serve as the model organism, Takifugu obscurus, a juvenile euryhaline fish, was exposed to different ZnO NPs concentrations (0–200 mg/L) and salinity levels (0 and 15 ppt). The results showed that a moderate increase in salinity (15 ppt) could alleviate the toxic effect of ZnO NPs, as evidenced by improved survival rates. The integrated biomarker response index on oxidative stress also revealed that the toxicity of ZnO NPs was higher in freshwater compared to brackish water. These outcomes can be attributed to higher salinity (15 ppt) reducing the bioavailability of ZnO NPs by facilitating their aggregation and inhibiting the release of metal ions. It is noteworthy that elevated salinity was found to alleviate ZnO NPs toxicity by means of osmotic adjustment via the activation of Na⁺/K⁺-ATPase activity. This study demonstrates the salinity-dependent effect of ZnO NPs on T. obscurus, suggesting the possibility for euryhaline fish like T. obscurus to adapt their habitat towards more saline environments, under constant exposure to ZnO NPs.

氧化锌纳米粒子（ZnO NPs）的广泛利用因其对生态系统的有害影响而引起了人们的广泛关注。不幸的是，氧化锌纳米粒子在盐度波动的沿海水域中的生态毒性已被忽视。本研究主要讨论了ZnO NPs对生活在淡水和咸水过渡带的物种的毒性作用，这些物种对鱼类具有重要的生态和经济重要性。为了作为模型生物，暗纹东方鲀（一种广盐鱼幼鱼）被暴露于不同的 ZnO NP 浓度（0–200 mg/L）和盐度水平（0 和 15 ppt）。结果表明，适度增加盐度（15 ppt）可以减轻 ZnO NP 的毒性作用，存活率的提高就证明了这一点。氧化应激的综合生物标志物响应指数还表明，与微咸水中相比，ZnO NPs 在淡水中的毒性更高。这些结果可归因于较高的盐度 (15 ppt) 通过促进 ZnO NP 的聚集和抑制金属离子的释放而降低了 ZnO NP 的生物利用度。值得注意的是，盐度升高可通过激活 Na ⁺ /K ⁺ -ATPase 活性来调节渗透压，从而减轻 ZnO NPs 的毒性。这项研究证明了 ZnO NPs 对暗带鱼的盐度依赖性影响，表明像暗带鱼这样的广盐鱼在持续暴露于 ZnO NPs 的情况下，有可能使它们的栖息地适应盐度更高的环境。