The Metabolic Theory of Ecology (MTE) has received a lot of attention in recent years. The theory is based on individual body size and temperature, and makes predictions on general characteristics of ecosystems, communities, and organisms.
We tested if the Metabolic Theory of Ecology (MTE) correctly predicts plankton metabolism in a temperate lake, based on a long-term (ca. 15 years), high-frequency dataset of body size, biomass and production. We fitted the estandard MTE model to the data two different techniques: Least Squares Regression and Maximum Likelihood.
Results/Conclusions
For phytoplankton, the general fit was poor (r2= 0.53), and the two main assumptions of the MTE were not supported: the allometric exponent (b) was significantly higher than ¾, and temperature played a negligible role in predicting the metabolic activity. When radiation was included as an additional predictor, it improved the model considerably (r2= 0.67). Including grazing by zooplankton improved the predictions during the summer period, when grazing is a dominant factor. The allometric exponent had virtually no effect for phytoplankton, due to little variability in average individual size. Zooplankton production, on the other hand, was better predicted by MTE, showing stronger effects of temperature and body size, which varied by a factor of more than a hundred. However, the best-fitting value of the allometric exponent for zooplankton was 0.85, also higher than the ¾ predicted by the theory.
Conclusions
We conclude that the MTE has little predictive power for the metabolism of lacustrine plankton, in particular for phytoplankton, and especially at the scale of variability of this study, and that this could be improved incorporating radiation into the model.
