Acclimation to warm temperatures has important implications for mitochondrial function in Atlantic salmon (Salmo...

Area of Science:

• Physiology
• Environmental Science
• Marine Biology

Background:

• Understanding fish thermal tolerance is crucial for predicting impacts of climate change on aquatic ecosystems.
• Cardiac mitochondrial function is central to fish thermal tolerance, influencing energy metabolism and performance.
• Thermal acclimation capacity is key to how fish cardiac mitochondria cope with rising ocean temperatures.

Purpose of the Study:

• To investigate the effects of chronic and acute warming on Atlantic salmon cardiac mitochondrial respiration and ROS production.
• To compare the sensitivity of mitochondrial respiration to nitric oxide (NO) and assess responses to anoxia-reoxygenation (AR).
• To determine if thermal acclimation enhances cardiac mitochondrial resilience to combined stressors.

Main Methods:

• Atlantic salmon were acclimated to 12°C and 20°C for over two months.
• High-resolution fluorespirometry was used to measure cardiac mitochondrial respiration, ROS production, and NO sensitivity (NO IC50).
• Mitochondrial responses to acute warming and anoxia-reoxygenation (AR) were assessed.

Main Results:

• Acclimation to 20°C preserved mitochondrial coupling and aerobic capacity, reduced ROS production by ~30%, and increased NO sensitivity.
• Acute warming to 20°C increased respiration but also lowered the respiratory control ratio and elevated ROS production.
• Warm acclimation did not improve mitochondrial recovery from AR, indicating no cross-tolerance to combined stressors.

Conclusions:

• Thermal plasticity in Atlantic salmon cardiac mitochondria supports prolonged survival at higher temperatures.
• Acclimation enhances mitochondrial function under warming but does not confer resilience against combined stressors like AR.
• The findings question the extent to which thermal plasticity can protect fish from future warming combined with other environmental challenges.