When mobilized from surrounding soils and binding to gills at moderately low pH, aluminum (Al) cations can adversely affect fish populations. Furthermore, acidification may lead to allostatic overload, a situation in which the costs of coping with chronic stress affects long-term survival and reproductive output and, ultimately, ecosystem health. The brain's serotonergic system plays a key role in neuroendocrine stress responses and allostatic processes. Here, we explored whether sublethal effects of Al in acidified water affects serotonergic neurochemistry and stress coping ability in a unique land-locked salmon population from Lake Bygelandsfjorden, in southern Norway. Fish were exposed to untreated water with pH 6.5 and 74 μg Al l-1 or acidified (pH 5.5) water with different aluminum concentrations ([Al]; 74-148 μg l-1) for 5-6 days. Afterward, effects on stress coping ability were investigated by analyzing plasma cortisol levels and telencephalic serotonergic neurochemistry before and after a standardized acute stress test. Before the stress test, positive dose-response relationships existed between [Al], serotonergic turnover rate and plasma cortisol. However, in acutely stressed fish, exposure to the highest [Al] resulted in reduced cortisol values compared with those exposed to lower concentrations, while the positive dose-response relationship between Al concentrations and serotonergic turnover rate persisted in baseline conditions. This suggests that fish exposed to the highest Al concentration were unable to mount a proper cortisol response to further acute stress, demonstrating that neuroendocrine indicators of allostatic load can be used to reveal sublethal effects of water acidification-and potentially, the environmental impacts of other factors.

中文翻译：

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内分泌负荷的神经内分泌指标显示了鱼类体内环境酸化的影响。

当从周围的土壤中迁移出来并在中等pH值下与binding结合时，铝（Al）阳离子会对鱼类种群产生不利影响。此外，酸化可能会导致异源性超负荷，在这种情况下，应付长期压力的成本会影响长期生存和生殖产出，并最终影响生态系统健康。大脑的血清素能系统在神经内分泌应激反应和异位过程中起关键作用。在这里，我们探讨了在酸性铝中铝的亚致死效应是否会影响挪威南部Bygelandsfjorden湖独特的内陆鲑鱼种群的血清素能神经化学和应激应对能力。将鱼暴露于pH 6.5和74μgAl l-1的未经处理的水或不同铝浓度（[Al]; 74-148μgl-1）的酸化（pH 5.5）的水中5-6天。随后，通过分析标准化急性应激测试前后的血浆皮质醇水平和端脑血清神经营养神经化学，研究了其对应激应对能力的影响。在压力测试之前，[Al]，血清素能转换率和血浆皮质醇之间存在正剂量反应关系。但是，在紧张状态下的鱼类中，暴露于最高浓度的[Al]与暴露于较低浓度的鱼类相比，皮质醇值降低，而在基线条件下，Al浓度和血清素能转换率之间的正剂量反应关系仍然存在。这表明暴露于最高Al浓度的鱼无法对进一步的急性应激产生适当的皮质醇反应，