Friday, August 10, 2007 - 10:50 AMCOS 160-9: Community respiration rate scales with temperature and nutrient availability in lake systems
April Hayward, Simon Grafe, and Jurek Kolasa. McMaster University
There is growing interest in the idea that organism metabolic rate – and its dependence on size, temperature, and stoichiometry – can be scaled up to predict patterns in structure and resource use for populations, communities, and ecosystems (“the Metabolic Theory of Ecology”). Here we use Metabolic Theory to derive predictions for the scaling of ecosystem metabolism and test these predictions using direct measurements of community respiration rate obtained from the literature for 59 lakes from around the globe. In accordance with Metabolic Theory, we find community respiration scales with temperature and resource availability. However, the temperature and resource scaling exponents depart from metabolically-derived expectations. First, community respiration is less responsive to changes in ambient temperature than expected based on the temperature-dependence of organism metabolism alone. Second, community respiration tracks resource availability with an exponent less than unity. The latter finding implies a decrease in nutrient use efficiency with increasing resource availability. In light of these findings and results obtained previously for similar work in aquatic microcosms we suggest the addition of a mass-dependent ‘resource storage’ term to the equation predicting the scaling of ecosystem respiration with temperature and resource availability.