Elemental Homeostasis at the Individual, Guild and Ecosystem Levels

Sterner

DEB 9815597

Organisms tend to be more invariant in the internal nutrient content that their surrounding environments. This phenomenon, homeostasis, is a central factor in ecological stoichiometry. In aquatic ecosystems, zooplankton exhibit substantially less variability in their nutrient content than the phytoplankton that they consume. In this project, nutrient homeostasis will be examined at the population, community and ecosystem level using a combination of laboratory and field investigations. Laboratory experiments will focus on five species of zooplankton chosen for their wide range of nutrient contents. Animals will be fed food with different nutrient ratios and the time scales of animal response will be evaluated. In field projects, the nutrient chemistry of food resources, zooplankton and fishes will be compared across a set of 60 lakes in Minnesota representing a north-south cline. It is hypothesized that chemical variability will decrease moving up the lakes' food chains from algae to fish. The project will test for a combination of positive and negative correlations across trophic levels in the different habitats.