Towards predicting community level effects of climate change: Relative temperature scaling of metabolic and ingestion rates for a suite of rocky intertidal consumers

Background/Question/Methods

Predicting the effects of climate change on ecological communities requires a fundamental understanding of how environmental factors influence both physiological and interspecific processes. Specifically, the net impact of temperature on community structure depends on the relative response of physiological energetic costs (basal metabolism) and interspecific gains (ingestion) that mediate the flow of energy throughout a food web. However, the relative scaling of metabolic and ingestion rates with temperature have never been measured for an entire ecological assemblage and it is not known how, and to what extent, they differ. To investigate the relative influence of these processes, I measured the temperature scaling of basal metabolic and ingestion rates for a suite of rocky intertidal species using a multiple regression experimental design. I compared oxygen consumption rates (as a proxy for basal metabolic rate) and ingestion rates by estimating the temperature scaling parameter (E_A; the activation energy) of the ‘universal temperature dependence’ (UTD) model, a theoretical model derived from first principles of biochemical kinetics and allometry.

Results/Conclusions

Consumer basal metabolic rates were more sensitive to temperature than ingestion rates. Thus, as temperature increased, metabolic rates tended to increase faster relative to ingestion rates. Metabolic and ingestion rates largely scaled in accordance with the UTD model; however, convex curvature was evident in several cases. Although these results indicate that short-term species interaction strengths will increase under warmer conditions, prior modeling exercises suggest that long-term energetic efficiencies and species interaction strengths would decline. Under warmer conditions this would increase population stability, with fewer fluctuations in population densities over time, but also increase the risk of starvation and extinction of top trophic levels. These results highlight the relative importance of interspecific processes for forecasting temperature effects on ecological communities and the importance of measuring the effects of environmental factors in ways that can be easily incorporated into community models.