Environmentally relevant methylmercury exposure reduces the metabolic scope of a model songbird

• Published in: Environmental pollution (1987) 2019-03, Vol.246, p.790-796
• Main Authors: Gerson, Alexander R., Cristol, Daniel A., Seewagen, Chad L.
• Format: Article
• Language: English
• Subjects: Basal metabolic rate; Eco-toxicology; Mercury exposure; Ornithology; Peak metabolic rate
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2018.12.072

For most birds, energy efficiency and conservation are paramount to balancing the competing demands of self-maintenance, reproduction, and other demanding life history stages. Yet the ability to maximize energy output for behaviors like predator escape and migration is often also critical. Environmental perturbations that affect energy metabolism may therefore have important consequences for fitness and survival. Methylmercury (MeHg) is a global pollutant that has wide-ranging impacts on physiological systems, but its effects on the metabolism of birds and other vertebrates are poorly understood. We investigated dose-dependent effects of dietary MeHg on the body composition, basal and peak metabolic rates (BMR, PMR), and respiratory quotients (RQ) of zebra finches (Taeniopygia guttata). Dietary exposure levels (0.0, 0.1, or 0.6 ppm wet weight) were intended to reflect a range of mercury concentrations found in invertebrate prey of songbirds in areas contaminated by atmospheric deposition or point-source pollution. We found adiposity increased with MeHg exposure. BMR also increased with exposure while PMR decreased, together resulting in reduced metabolic scope in both MeHg-exposed treatments. There were differences in RQ among treatments that suggested a compromised ability of exposed birds to rapidly metabolize carbohydrates during exercise in a hop-hover wheel. The elevated BMR of exposed birds may have been due to energetic costs of depurating MeHg, whereas the reduced PMR could have been due to reduced oxygen carrying capacity and/or reduced glycolytic capacity. Our results suggest that environmentally relevant mercury exposure is capable of compromising the ability of songbirds to both budget and rapidly exert energy. [Display omitted] •Exposure to an environmentally relevant concentration of dietary methylmercury (0.6 ppm) significantly increased the basal metabolic rates of zebra finches by 19%, and reduced the peak metabolic rates of zebra finches by 23%.•Together, this resulted in a 31% average reduction in the overall metabolic scope of zebra finches exposed to 0.6 ppm dietary methylmercury.•Environmentally relevant methylmercury exposure can compromise the ability of birds to both conserve and rapidly exert energy, which is likely to have negative consequences for reproduction, migration, predator escape, and other important behaviors. Environmentally relevant exposure to mercury increases adiposity, increases basal metabolic rate, and reduces p