Element Linkage and Growth-Competition Tradeoffs in Freshwater Zooplankton

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This project will explore a new and general model that ties together three parameters - an organism's growth rate, its elemental composition, and a new parameter referred to as catalysis power - to predict that there will be a tradeoff between growth rate and competitive ability when the concentration of one element controls changes in another. The model, called the Elemental Linkage Model, is highly general and makes a single assumption - that organisms maintain balanced growth or equal specific rates of change of all elements within organism biomass. Considerable previous work on phosphorus concentrations in freshwater zooplankton supports the application of the Element Linkage model to these organisms. This project will focus on the growth-competition tradeoff the model predicts. Food threshold experiments (to measure growth rates) and competition trials will be initiated using seventeen species of cladoceran zooplankton and six clones of one species to compare predictions of the Elemental Linkage Model at several taxonomic levels. These comparisons will be used to detect interspecific growth-competition tradeoffs, which the linkage model predicts will occur on low-P but not high-P foods. These experiments explore thoroughly this tradeoff using an otherwise well-known experimental system and extend the application of stoichiometric (nutrient abundances and ratios) models to competitive interactions. Broader impacts of the research will be to advance a potentially important new model in ecology. Career and educational opportunities will be generated for the PI, a graduate student, a technician and extended to undergraduates and high school teachers, who will participate in the project via ongoing University of Minnesota initiatives.