The hypolimnion is the dense, bottom layer of water in a stratified lake, typically found below the thermocline. This layer is characterized by lower temperatures and reduced light penetration, making it less hospitable for aquatic life compared to the upper layers. The hypolimnion can become isolated from the upper layers, leading to differences in oxygen levels and nutrient availability. During the summer, the hypolimnion remains stable and cold, while the upper layer, known as the epilimnion, warms up. In some lakes, the hypolimnion can become anoxic, meaning it lacks oxygen, which can affect the overall health of the lake ecosystem. Understanding the hypolimnion is essential for studying lake dynamics and the impact of seasonal changes on aquatic environments.