The hypolimnion is the dense, cold layer of water found at the bottom of a stratified lake. It typically remains isolated from the warmer, upper layers, known as the epilimnion, especially during the summer months. This layer is characterized by lower temperatures and reduced light penetration, which affects the types of organisms that can thrive there. In many lakes, the hypolimnion can become anoxic, meaning it lacks oxygen, particularly in the absence of mixing. This can lead to the accumulation of nutrients and organic matter, impacting the overall health of the lake ecosystem. Understanding the hypolimnion is essential for studying lake dynamics and aquatic life.