Freshwater acidification is a global environmental challenge, yet the effects of acidic water on fish resistance to toxic Ag remain an unexplored area. To address this knowledge gap, zebrafish embryos were exposed to different concentrations (0 (control), 0.1, and 0.25 mg/L) of AgNO under pH 5 or 7 for 7 days. Notably, AgNO at 0.25 mg/L resulted in 100 % mortality in both pH conditions, while AgNO at 0.1 mg/L resulted in higher mortality at pH 5 (85 %) compared to pH 7 (20 %), indicating that acidic water enhanced Ag toxicity. Several parameters, including body length, inner ear (otic vesicle and otolith) and yolk sac areas, lateral line hair cell number and morphology, the number of ionocytes (-ATP-rich cells and Na/-ATP-rich cells), and ion contents (Ag, Na, and Ca) were assessed at 96 h (day 4) to investigate individual and combined effects of Ag and acid on embryos. Acid alone did not significantly alter most parameters, but it decreased the yolk sac area and increased the ionocyte number. Conversely, Ag alone caused reductions in most parameters, including body length, the inner ear area, hair cell number, and ionocyte number. Combining acid and Ag resulted in greater suppression of the otolith area, hair cell number, and Na/Ca contents. In conclusion, acidification of freshwater poses a potential risk to fish embryo viability by increasing their susceptibility to silver toxicity, specifically affecting sensory function and ion regulation.

中文翻译：

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酸化水促进银对斑马鱼胚胎的毒性

淡水酸化是一个全球性的环境挑战，但酸性水对鱼类对有毒银的抵抗力的影响仍然是一个尚未探索的领域。为了弥补这一知识差距，将斑马鱼胚胎在 pH 5 或 7 下暴露于不同浓度（0（对照）、0.1 和 0.25 mg/L）的 AgNO 中 7 天。值得注意的是，0.25 mg/L 的 AgNO 在两种 pH 条件下均导致 100% 的死亡率，而 0.1 mg/L 的 AgNO 导致 pH 5 时的死亡率 (85%) 高于 pH 7 时的死亡率 (20%)，这表明酸性水增强了银毒性。几个参数，包括体长、内耳（耳囊和耳石）和卵黄囊面积、侧线毛细胞数量和形态、离子细胞（富含 -ATP 的细胞和富含 Na/-ATP 的细胞）的数量以及离子在第 96 小时（第 4 天）评估银、钠和钙的含量，以研究银和酸对胚胎的单独和组合影响。单独的酸不会显着改变大多数参数，但它会减少卵黄囊面积并增加离子细胞数量。相反，单独使用银会导致大多数参数减少，包括体长、内耳面积、毛细胞数量和离子细胞数量。酸和银的结合导致对耳石面积、毛细胞数量和 Na/Ca 含量的更大抑制。总之，淡水酸化会增加鱼类胚胎对银毒性的敏感性，特别是影响感觉功能和离子调节，从而对鱼类胚胎的生存能力构成潜在风险。