Population dynamics and stoichiometry of consumer-resource systems: a combined experimental and modelling approach

A recent approach in ecology, ecological stoichiometry, recognises resource quality (nutrient ratios) as a limiting factor in addition to resource quantity. In the proposed project, we will apply this approach to study classical population-ecological prob lems in a new perspective. Theoretical models of consumer resource systems have predicted dramatic and counter-intuitive changes in population dynamics, when nutrient recycling and nutrient-limited growth are considered. However, most of these models are not yet evaluated experimentally. An important prediction is that increased phosphorous enrichment leads to more unstable population dynamics of the consumer, and eventually to extinction, although the resource persists. We will test this prediction by e xposing laboratory systems of zoopl ankton (Daphnia) and algae to a range of phosphorous concentrations, and study the long-term dynamics of the system. Using ion-parametric modelling, we aim at developing a new statistical]y-derived model for this system . Such models make Few a priori assu mptions about the form of the functions, and are therefore well-suited for exploring unknown relationships among variables. By combining such a flexible modelling approach with the stoichiometric perspective, we expect to provide new insight into general ecological problems.