DISSERTATION RESEARCH:Ecological Stoichiometry and Predation: Examining Life History Trade-Offs in Daphnia

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Daphnia, the water flea, is an integral component of the lake ecosystem. Many aspects of Daphnia biology have been well characterized, including the role of food quality constraints on growth and reproduction, the dynamics of predator-prey interactions, and the complete genome sequence, making it an ideal model organism for an integrated examination of the chemical, environmental, and molecular components of ecology. This project investigates the effect of food quality and predation on Daphnia life history, including growth rate and reproductive output, by quantifying a set of visible traits produced by the interaction between the genotype and a range of environmental conditions (reaction norms). Predictions based on laboratory results will be tested in the field, providing an opportunity to relate nutrition to predation in a natural environment. The research addresses the importance of food quality, predation, and genotypic variation on species interactions and community stability in the lake ecosystem. The results obtained will increase awareness of the importance of elemental ratios in the environment and the impact on organismal composition and ecosystem function.The broader objective of the project is a more complete understanding of the complexity of the aquatic ecosystem. By incorporating chemical, physiological, and molecular approaches to understand ecosystem dynamics, the impact of human-induced environmental change, particularly the eutrophication of lakes via phosphorus enrichment, can be predicted at the molecular, individual, and food web levels. Given the growing stress on the lake environment worldwide, an increased understanding of the consequences of anthropogenic modification of freshwater ecosystems is vitally important.