Global warming significantly impacts the persistence of species, food web dynamics, habitat characteristics and ecosystem services. As ambient temperature increases, one of the most observed consequences are changes in individual sizes. These shifts in body size impact both individual species capacity as well as the broader environment. In a structured aquatic community, species often have a size-specific ingestion capacity, and their survival and their number of offspring are highly size-dependent. To understand the mechanisms behind the shifts in body size and to project future population trends, researchers experiment with water flea Daphnia magna in the Limnotron Facility, the world's largest freshwater mesocosm. The purpose of the project is to understand how increases in water temperature affect the population size structure of daphnia. A projection model will be constructed to predict daphnia population trends and to examine how these changes impact population dynamics. Specifically, researchers are working with six tanks with the capacity to each hold 26,000L of water. Three tanks are set at 15oC while the other three are at 25oC. For each temperature treatment, one tank with be filled only with Chlorella vulgaris, a species acting as the water flea primary food source, and 2 tanks with receive both the water flea Daphnia magna and the Chlorelia vulgaris.