Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
Gitga'at Lands and Resources Stewardship Society, 445 Hayiimisaxaa Way, Hartley Bay, BC, V0V 1A0, Canada.
Fish Physiol Biochem. 2012 Aug;38(4):1131-1143. doi: 10.1007/s10695-011-9599-4. Epub 2012 Jan 22.
Chronic exposure to water of low pH during the freshwater life stage of Pacific salmonids is presently the cause for concern due to its potential to reduce subsequent performance in the marine environment. Sockeye fry (0+) were raised under sublethal long-term, low pH conditions (pH 4.8-6.8) in soft water and assessed for effects on freshwater growth, stress physiology, and seawater tolerance following smoltification. Fish gained significantly lower mass (average 46% of control [pH 6.8] values) and had lower condition factor and liver somatic index values than control fish following a 126-days exposure to water at pH 5.0. Liver glycogen concentrations (49% of control values) and whole-body lipid content (65% of control values) were also significantly lower. Low pH exposure also resulted in a sustained organismal stress response that included significant and substantial increases in plasma cortisol concentrations. Fish exposed to pH 5.0 in freshwater for 30 days exhibited an average of 14% mortality in a seawater challenge, as well as a significant osmoregulatory stress measured by increases in plasma Na⁺ and Cl⁻ concentrations as well as osmolality compared to controls. Significantly lower critical swimming speed values (U(crit)) were also seen (22% reductions compared to controls). The data generated indicate that sockeye salmon are sensitive and do not acclimate to low pH under long-term exposure conditions, potentially decreasing the probability of survival in the marine environment.
慢性暴露于低 pH 值的水中是目前太平洋鲑鱼淡水生活阶段令人担忧的原因，因为它可能会降低它们在海洋环境中的后续表现。在软水中，将太平洋红大麻哈鱼鱼苗（0+）置于亚致死的长期低 pH 值条件（pH4.8-6.8）下进行培养，并在变态为幼鱼后评估对淡水生长、应激生理和海水耐受性的影响。与对照组（pH6.8）相比，在 pH5.0 的水中暴露 126 天后，鱼的体重显著降低（平均为对照组的 46%），且条件系数和肝体比指数值也较低。肝糖原浓度（为对照组的 49%）和全身体脂含量（为对照组的 65%）也明显较低。低 pH 值暴露还导致了持续的机体应激反应，包括血浆皮质醇浓度的显著和实质性增加。在海水中进行挑战时，在淡水中暴露于 pH5.0 的鱼有 14%的平均死亡率，与对照组相比，血浆 Na⁺和 Cl⁻浓度以及渗透压的升高表明存在显著的渗透调节应激。临界游泳速度（Ucrit）值也明显较低（与对照组相比降低了 22%）。生成的数据表明，太平洋红大麻哈鱼对低 pH 值敏感，并且在长期暴露条件下不能适应低 pH 值，这可能降低了它们在海洋环境中的生存概率。
