Freshwater Ecology is the study or organisms, the environment, and how they interact in that environment. By studying this the scientists can learn about patterns and about what different organisms need to survive and live. We need to learn about these ecosystems in order to protect them. A difference between a pond and a river is that a river contains more oxygen. Another difference is that a pond is sitting water while a river is flowing. Finally, water in a pond will remain there while a river will empty into a much larger body of water or the ocean.