metalimnion

The metalimnion is a layer within a lake where the temperature changes rapidly with depth, also known as the thermocline. This layer is situated between the warmer upper layer (epilimnion) and the colder lower layer (hypolimnion). In temperate regions, lakes typically stratify in the summer, with the epilimnion warming and ceasing to mix with the hypolimnion. The metalimnion acts as the boundary between these two distinct thermal layers. As autumn progresses, the epilimnion cools, causing the water to become denser and sink, leading to mixing between the layers and the eventual elimination of stratification. This thermal stratification significantly influences the movement of nutrients and dissolved oxygen within the lake, impacting the overall ecology.123