Sewage run-off into large bodies of water can result in the formation of dead zones because excess nutrients naturally cause the dense growth of algae. The decomposition of these dense growths causes oxygen depletion through the process of eutrophication. To create a dead zone model, yeast will be used as the decomposers, milk as the run-off (nutrients), and methylene blue as an oxygen indicator. Students will learn that the process of decomposition takes in oxygen and releases carbon dioxide as a by-product, creating hypoxic conditions for marine life.