Diet mediates thermal performance traits: implications for marine ectotherms

Thermal acclimation is a key process enabling ectotherms to cope with temperature change. To undergo a successful acclimation response, ectotherms require energy and nutritional building blocks obtained from their diet. However, diet is often overlooked as a factor that can alter acclimation responses. Using a temperate omnivorous fish, opaleye (Girella nigricans), as a model system, we tested the hypotheses that 1) diet can impact the magnitude of thermal acclimation responses and 2) traits vary in their sensitivity to both temperature acclimation and diet. We fed opaleye a simple choice omnivorous diet (ad libitum Artemia sp. and Ulva sp.) or a fixed carnivorous diet (ad libitum Artemia sp.) at two ecologically relevant temperatures (12 and 20°C) and measured a suite of whole animal (growth, sprint speed, metabolism), organ (cardiac thermal tolerance), and cellular-level traits (oxidative stress, glycolytic capacity). When opaleye were offered two diet options compared to one, they ha...