What is a key characteristic of the thermocline layer in a thermally stratified lake?

The thermocline is a critical layer in a thermally stratified lake characterized by a significant and rapid decrease in temperature with depth. This layer typically separates the warmer, well-mixed upper layer, or epilimnion, from the colder, denser lower layer, or hypolimnion. During warmer months, sunlight warms the surface waters, creating a distinct temperature gradient that is most pronounced in the thermocline. As you move down through this layer, the water temperature drops sharply, indicating the largest temperature change occurs within this zone.

This characteristic of the thermocline is essential for understanding the stratification of lakes, as it influences the distribution of aquatic life and the mixing of nutrients. While other layers may have specific conditions, the thermocline itself is defined by this rapid temperature decline, making it a unique and important component of lake ecology.