Expressed more technically, the mere consists entirely of the epilimnion.

During the colder fall season, heat is lost at the surface and the epilimnion cools.

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

The upper warm zone is called the epilimnion.

The epilimnion is oxygen rich because it circulates quickly, gaining oxygen via contact with the air.

The top layer of water (epilimnion) is warmed by the sun and sits atop the metalimnion (also a thermocline).

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

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

Conversely, for most of the time, the relatively shallower meres are unstratified; that is, the mere is considered all epilimnion.

In a lake, photosynthesis is limited to the epilimnion, where the depletion of nutrients cannot be replaced from the hypoplimnion until mixing occurs in winter.

Thermal stratification divides the pond into two parts: the upper layer (epilimnion) and the lower layer (hypolimnium).

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

During summer they are thermally stratified, with temperature-derived density differences separating the warm surface waters (the epilimnion), from the colder bottom waters (the hypolimnion).

Cold water is denser than warm water and the epilimnion generally consists of water that is not as dense as the water in the hypolimnion.

Many soda lakes are strongly stratified, with well-oxygenated upper layer (epilimnion) and an anoxic lower layer (hypolimnion), without oxygen and often high concentrations of sulfide.

As they grow and reproduce they absorb nutrients from the water, when they die they sink into the hypolimnion resulting in the epilimnion becoming depleted of nutrients.

Down there the temperature was always an even 4, no matter what the season, but it was unheard of that a spore should be found there while the high epilimnion was still warm and rich in oxygen.

The northwest to southeast orientation of Uvas Reservoir is in line with prevailing winds which drive the warm surface layer (epilimnion) down into the cool bottom layer (hypolimnion), so that by late summer the bottom water is warm and anoxic.

As summer advances a layer of warmer water (12 o C at the surface and falling with depth), termed the epilimnion, separates from the hypolimnion beneath, which remains at 5.6 o C. The boundary layer where the temperature changes abruptly is the thermocline.

In all but the shallowest lakes, there are major changes in the chemical composition of lake water at different depths, especially during the summer months when many lakes stratify into a warm, well oxygenated upper layer (epilimnion) and a cool de-oxygenated lower layer (hypolimnion).