Testing the metabolic theory of ecology with the help of temperature-controlled phytoplankton experiments

Informations

Funding country

Netherlands

Acronym

-

URL

-

Start date

7/1/2009

End date

12/18/2014

Budget

-

Fundings

Abstract

In this project we will investigate the effects of temperature on the dynamics and diversity of phytoplankton in microcosm experiments. Our main goal is to test some crucial predictions of the Metabolic Theory of Ecology (MTE). MTE is an intriguing but controversial theory that attempts to explain ecological patterns at all scales on the basis of biochemical principles. Temperature plays a pivotal role in this theory. According to MTE, the Arrhenius law for the effect of temperature on biochemical reactions extends to a universal tem¬perature dependence (UTD) that includes all kinds of whole-organism processes (e.g. individual metabolism, growth, reproduction, mortality) and even scales up to the level of populations and communities. We will test these predictions in a series of controlled phytoplankton experiments. We design three sets of experiments with increasing complexity, ranging from monocultures in a constant environment to a multi-species community under fluctuating temperature. Each experiment consists of a series of continuous cultures. In the first experiment, monocultures are used to investigate how temperature affects the morphology, physiology and growth of various phytoplankton species. This experiment will yield insights into whether UTD does indeed hold at the level of the population (population metabolism, maximal growth rate, equilibrium density). In particular, we will test the energetic-equivalence rule that predicts a relatively simple relationship between equilibrium density and temperature. Moreover, we will address the role of thermal acclimation that is often overlooked in applications of MTE. In the second experiment, we will investigate the temperature depend¬ence of growth and competition of small communities consisting of two phytoplankton species varying in relative abundance. This experiment will test one of the central and most controversial predictions of MTE that ? at steady state ? community metabolism is temperature invariant and independent of the species composition and the relative abundance of the constituent species. We will get insights into whether UTD does indeed hold at the community level, a crucial assumption for predicting global biodiversity trends. In a third experiment, both monocultures and mixed cultures will be exposed to various degrees of temperature fluctuation. Such fluctuations are of obvious relevance in natural ecosystems, but they have not got much theoretical attention. The experiment, which may be an important test case for the robustness of MTE, addresses the question whether the effects of temperature fluctuations average out, or whether the resulting changes in species composition and abundance lead to strong deviations from UTD. The project is designed in such a way that all experiments can also be interpreted in the light of Resource Competition Theory (RCT), a second major theory for explaining the structure and dynamics of commun¬ities. While MTE is based on energy considerations, the focus of RCT is on limiting resources like nutrients or light. Throughout the project, we will investigate whether metabolic aspects are affected by resource limitation and, conversely, how temperature affects the outcome of resource competition. This way, we will provide much needed experimental evidence for the current attempts to integrate MTE and RCT into a unified theory of biodiversity.