The seasonal response of metabolic rate to projected climate change scenarios in aquatic amphipods

The responses of organisms to climate change are mediated primarily by its impact on their metabolic rates, which, in turn, drive various biological and ecological processes. Although there have been numerous seminal studies on the sensitivity of metabolic rate to temperature, little is empirically known about how this rate responds to seasonal temperature ranges and beyond under conservative IPCC climate change scenarios. Here, we measured the SMR of the aquatic amphipod, Gammarus insensibilis, which served as our subject species, with body masses ranging from 0.20 to 7.74 mg ash free weight. We assessed the response of the SMR across nine temperature levels ranging from 12 to 30.2 °C. These temperatures match seasonal temperature norms, with an incremental increase of 0.6-1.2 °C above each seasonal baseline, as projected for the years 2040 and 2100 under the modest climate change scenarios. Overall, our findings showed that the effect of temperature on SMR varies with body mass, as indicated by a negative size-temperature interaction, with larger conspecifics exhibiting less sensitivity to temperature changes than smaller ones. From the cold to warm season, the SMR increased by an average of 14% °C