Niva, Norsk institutt for vannforskning, Gaustadalléen 21, NO-0349 Oslo, Norway; Center of Coastal Research, University of Agder, 4604 Kristiansand, Norway. Electronic address: erik.hoglund@niva.no.
Source
Comp Biochem Physiol C Toxicol Pharmacol. 2020 Mar; 229:108679
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.