The hypolimnion, however, circulates very slowly and has no atmospheric contact.

The hypolimnion is the dense, bottom layer of water in a thermally-stratified lake.

Above the hypolimnion is a thin layer, known as epilimnion, where fish survive to some degree.

The lowest zone in the lake is the coldest and is called the hypolimnion.

As the plants die in the late summer they fall into the cool water layers underneath - the hypolimnion - and decompose.

The hypolimnion may be much warmer in lakes at warmer latitudes.

Additionally, fewer green plants exist in the hypolimnion, so there is less oxygen released from photosynthesis.

The outlet provides a laminar flow and a horizontal outflow into the hypolimnion.

In deep, temperate lakes, the bottom-most waters of the hypolimnion are typically close to 4 C throughout the year.

Typically the hypolimnion is the coldest layer of a lake in summer, and the warmest layer during winter.

This causes the lake water to degenerate into a eutrophic condition, creating a dead water zone called the hypolimnion.

The hypolimnion is now not only hostile, but the anaerobic conditions also cause increased phosphate dissolutions from the sediments into the deep water.

The lake is thus anoxic and has reduced hypolimnion, winter circulation, large phytoplankton and relatively lower animal population.

In large water bodies, autumn turn-over can introduce oxygen rich water into the oxygen poor Hypolimnion.

The warm layer is called the epilimnion and the cold layer is called the hypolimnion.

Deep reservoirs with multiple level draw off towers can discharge deep cold water into the downstream river greatly reducing the size of any hypolimnion.

The epilimnion is the top-most layer in a thermally stratified lake, occurring above the deeper hypolimnion.

Minimal oxygen from the air diffuses down to the hypolimnion, causing very low dissolved oxygen (DO) levels.

In spring and fall when the epilimnion and hypolimnion mix, oxygen becomes more evenly distributed in the system (Brown 1987).

It is warmer and typically has a higher pH and higher dissolved oxygen concentration than the hypolimnion.

This trend is especially strong in the bottom layer (hypolimnion) of stratified lakes, probably because of the isolated character of such environments.

At the bottom of lakes (in the sediment or hypolimnion, methanogens use these compounds to derive energy, by producing methane, a procedure known as methanogenesis.

The density difference between the warm surface waters (the epilimnion) and the colder bottom waters (the hypolimnion) prevents these lakes from mixing in summer.

As the hypolimnion of lakes gradually filled with sediments, oxygen depletion would promote the release of iron-bound phosphorus to the overlying water.

The water of a deep reservoir in temperate climates typically stratifies with a large volume of cold, oxygen poor water in the hypolimnion.