Epilimnion Metalimnion and Hypolimnion

Epilimnion Meaning

What is the epilimnion of a lake?

The epilimnion of a lake is the uppermost layer of water in a body of water. It is typically warmer and less dense than the hypolimnion below it, which makes it more buoyant. It consists of cool water that has not been mixed with the gases and minerals from the bottom of the lake.

This layer is sometimes called the winter strata because it is usually quite cold. When looking into a lake, this water is located near the surface, where the sunlight illuminates it.

The epilimnion is where most of the photosynthesis and oxygen exchange takes place. The epilimnion is the most biologically active layer. The epilimnion receives direct sunlight from the water’s surface. In lakes, the epilimnion can have a maximum depth of 5 meters

Fish species that live in this region are adapted to living at these temperatures

Epilimnion Layer Characteristics

• The epilimnion is the top layer of a lake that sits above the thermocline. The thermocline is the temperature gradient between the water temperature of the surface and the bottom of the lake or river.
• The epilimnion is the thickest layer of the water column as it is in contact with the sun and the air.
• The temperature in this layer is usually 6-7 degrees Celsius.
• This layer is critical as it is where aquatic organisms live and reproduce
• The epilimnion of a lake is the upper layer of water that heats up during the day. It’s also called the summer water because it warms up quickly and cools off slowly.
• The epilimnion is usually less than 10 meters deep but can be as deep as 100 meters in some cases
• The epilimnion is the upper layer of water in a thermally stratified body of water.
• The epilimnion is warmer than the hypolimnion because it receives heat from the sun and warm air.
• Epilimnetic waters are usually rich in nutrients, such as nitrates, phosphates, and silicates.  In some cases, when there is an abundance of these nutrients in the epilimnion they can create algal blooms

Epilimnion Temperature

The epilimnion temperature is the water temperature of the top layer of a lake. Its temperature varies depending on how much sunlight falls on it.

It has a temperature that is higher than the water below it and lower than the air above it. This temperature difference creates convection currents, which mix oxygen into the deeper layers of water. These currents also bring nutrients up from deep waters to feed plankton at the surface

It is usually warmer than the bottom layer, which is called the hypolimnion.  The epilimnion and hypolimnion are separated by an interface where heat transfer occurs between them

Epilimnion Thickness

The epilimnion is the upper layer of water in a lake or pond that’s warmed by sunlight and typically has lower oxygen levels than the hypolimnion below.

The thickness of the epilimnion depends on how much heat energy it absorbs from the sun, which varies depending on latitude, season, and time of day.

Epilimnion thickness can be difficult to quantify due to its very thin nature. The epilimnion is the second layer of the water column in a lake or other body of water.

Difference between Epilimnion and Hypolimnion

Epilimnion: The epilimnion is the uppermost layer of water in a lake or other body of water, and is typically warmer than hypolimnion.

Hypolimnion: The hypolimnion is the lowermost layer of water in a lake or other body of water, and is typically colder than the epilimnion.

Epilimnion: The epilimnion is where most aquatic life can be found because they have greater oxygen content relative to that at deeper levels.

Hypolimnions: As sunlight penetrates into these areas it becomes more difficult for photosynthesis to take place so there are less plant and animal life.

Metalimnion Definition

What is Metalimnion?

Metalimnion is a layer of cold water at the bottom of the lake. It is created by a sinkhole or a hole formed by subsidence caused by over-fertilization followed by rapid freezing and thawing, which causes holes to form in the lake floor. The cold waters of metalimnion come from the depths where there is more water with lower temperatures.

Metalimnion formation is often the result of either over-fertilization or rapid freeze and thawing. The latter is caused by excessive pumping from fish hatcheries.

The metalimnion can be trapped by local factors like sedimentation, natural dams or construction projects which are carried out with the purpose of reclaiming the lake floor.

The metalimnion is filled with very cold water compared to the surrounding water. Water in this zone is also said to be bottom-heavy.

What is the use of Metalimnion?

Metalimnion can be used for a number of things such as:
Apart from being a fishery, some people do scuba diving, snorkeling and whale watching in the metalimnion.

Metalimnion advantages & disadvantages?

Main Advantages:

Metalimnion is a unique layer of water at the bottom of a lake. It is filled with freshwater even though it is very cold. The cold water of metalimnion is good for the plants, fishes, and other aquatic animals and can help them survive during winter. It also aids in preserving the shoreline and wildlife.

There are different uses for metalimnion such as fishing, scuba diving, snorkelling and whale watching. These uses make it an important part of the lake.

Main Disadvantages:

Metalimnion is a disadvantage because it could lead to the warming of the surface water by trapping heat. The trapped heat results in increasing the water temperature leading to the death of underwater organisms.
The hypolimnion and metalimnion are combined as one which means there is no separation between these two layers of water. In certain cases, both of these water layers become toxic because they have a higher rate of heavy metals.

What is the purpose of the metalimnion?

Metalimnion plays a very important role in the development of fish eggs and juveniles. Coldwater has a lot of oxygen which helps develop eggs. In colder waters, there are fewer predators hence it is safer to grow the young fishes.
In addition, metallicimnion is a sort of reservoir which provides feeding stock for people who engage in fishing activities at the lakesides.

How cold does the metalimnion get?

Metalimnion is the layer of water that is present at the bottom of a lake is between the epilimnion and hypolimnion. It is the coldest and deepest in a lake. This layer of water has a temperature below 5 degrees Celsius and above 0 degrees Celsius.

what are the effects of metalimnion?

Metalimnion can influence the growth of fish and aquatic organisms because it prevents sunlight from entering into water bodies. This in turn influences the aquatic life processes.

Why do we have Metalimnion?

Metalimnion gets formed when lakes freeze and thaw. Underwater currents cause ice formation at the lake’s surface in winter, which will be heavier than the water that flows into this area.
As a result, this cold water sinks to the bottom of the lake and this creates Metalimnion. Metalimnion formation can also occur due to environmental reasons like drought conditions or fluctuations in temperature etc.

Hypolimnion

The hypolimnion is the upper layer of water in a lake and is colder than the thermocline. Basically, it’s a cold band at the top of a lake that is sandwiched between an epilimnion and a bottom layer called the hypolimnetic zone. This zone includes all that’s below the thermocline. When the lake’s thermocline is sinking at a rate of one meter per day, the hypolimnion will have a temperature range of – 1.1C to 3.4C.

The hypolimnion is the lowest layer of water in a thermally stratified lake. Strictly speaking, it does not occur in rivers or estuaries because they are open systems and there is always an exchange between the surface waters (epilimnion) and the bottom water (hypolimnion). The depth of the hypolimnion ranges from a few feet in small lakes to about 200 feet in large lakes.

What is the depth and temperature of Hypolimnion?

The hypolimnion is located just below the thermocline and develops as a result of an upper layer that is warmed by the sun and a bottom layer colder than that top layer. The temperature of the water in the hypolimnion depends on how well mixed it is: warmer water cools more readily than colder water.

The main factor that influences how cold the hypolimnion gets is the region between the thermocline and bottom layer, known as the bottom water layer or BML or bmlc, usually about 2 meters (6 ft) deep. If the depth is less than 2 meters, the temperature range will be smaller; if it’s greater, it will be larger.

The BML layer often acts as a diffuser, preventing cold water from moving up near the surface. This is why you often see some areas at the lake’s edge where the surface is warm, while other areas at the same altitude are very cold.

The depth of the hypolimnion varies with the availability of sunlight and temperature but generally ranges from about 10 – 30 feet deep.