Lake stratification

Lake_Stratification_(11)

LSE_Stratification

Lake stratification is the separation of lakes into three distinct layers: the epilimnion, the metalimnion (or thermocline), and the hypolimnion. This phenomenon occurs due to differences in water temperature and density, which prevent the mixing of water layers.

Layers of Stratification

Epilimnion

The epilimnion is the topmost layer of a stratified lake. It is characterized by warmer water temperatures and higher levels of dissolved oxygen due to direct contact with the atmosphere and photosynthetic activity. This layer is typically well-mixed by wind and wave action.

Metalimnion

The metalimnion, also known as the thermocline, is the middle layer where there is a rapid change in temperature with depth. This layer acts as a barrier to the mixing of the upper and lower layers of the lake. The temperature gradient in the metalimnion is steep, and it plays a crucial role in the thermal structure of the lake.

Hypolimnion

The hypolimnion is the bottom layer of a stratified lake. It is characterized by colder, denser water and lower levels of dissolved oxygen. This layer is typically isolated from the atmosphere and receives little to no sunlight, resulting in limited biological activity.

Causes of Stratification

Lake stratification is primarily driven by temperature differences. During the warmer months, solar radiation heats the surface water, creating a temperature gradient. Wind and wave action mix the surface water, but the denser, colder water remains at the bottom, leading to the formation of distinct layers.

Seasonal Stratification

Lakes in temperate regions often undergo seasonal stratification. In the summer, lakes are typically stratified with a warm epilimnion, a thermocline, and a cold hypolimnion. In the winter, the surface water cools and can become denser than the water below, leading to a process called overturn, where the water layers mix. This mixing can bring nutrients from the bottom to the surface, supporting aquatic life.

Ecological Implications

Stratification has significant ecological implications. The separation of water layers can affect the distribution of nutrients and oxygen, influencing the types of organisms that can thrive in different parts of the lake. For example, the hypolimnion may become anoxic (depleted of oxygen) during stratification, which can impact fish and other aerobic organisms.

Related Pages

• Thermocline
• Epilimnion
• Hypolimnion
• Lake ecology
• Water density
• Seasonal stratification

See Also

• Thermal pollution
• Lake turnover
• Limnology