Predicting thermal sensitivity of three Amazon fishes exposed to climate change scenarios

Increased temperature and CO2 levels are predicts for the next decades. Tropical species are expected to be especially vulnerable to these alterations once many of them appear to have a narrower thermal tolerance range compared to subtropical and temperate species; and live closer to their thermal limits. Herein, we experimentally investigated the effects of climate change scenario on metabolic and oxidative stress in three ornamental fishes of Amazon forest streams. Apistogramma agassizii, Pyrhullina brevis and Hyphessobrychon melazonatus were exposed to current and extreme climate scenarios (4.5 °C and 900 ppm CO2 above current levels) and had respiratory profile, antioxidant enzymes and neurotransmitter responses evaluated. The integrated biomarkers response index (IBR) was calculated to examine specie’s acclimation abilities. After 30 days of exposure, we observed distinct physiological mechanisms to cope with climate change. Overall, Amazonian fish species are susceptible to climate change since they showed increase in metabolic rate and oxidative stress. Yet, sedentary ones A. agassizii and P. brevis, appeared to be less impacted by climate change than H. melazonatus, once they presented high survival rates, thermal tolerance and low IBR values. In contrast, H. melazonatus, an athletic species, low survival rates, lipid peroxidation, lower thermal tolerance and high IBR. This study provides evidence that future climate changes will affect energy supply and promote species-specific damages in metabolic pathways, with consequent physiological impairments, which may have detrimental effects at population and ecosystem levels.