Hypolimnion

Source: Wikipedia, the free encyclopedia.
Lakes are stratified into three separate sections:
I. The Epilimnion
II. The Metalimnion
III. The Hypolimnion
The scales are used to associate each section of the stratification to their corresponding depths and temperatures. The arrow is used to show the movement of wind over the surface of the water which initiates the turnover in the epilimnion and the hypolimnion.
Lake zones
   Littoral zone
   Limnetic zone
   Profundal zone
   Benthic zone
Lake stratification
   Epilimnion
  
Metalimnion
   Hypolimnion
   Destratification
Lake types
   Holomictic lake
   Monomictic lake
   Dimictic lake
   Polymictic lake
   Meromictic lake
   Amictic lake
See also

The hypolimnion or under lake is the dense, bottom layer of water in a thermally-

romanized: limníon, lit. 'lake'.[2] It is the layer that lies below the thermocline
.

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

temperate lakes, the bottom-most waters of the hypolimnion are typically close to 4 °C throughout the year. The hypolimnion may be much warmer in lakes at warmer latitudes. Being at depth, it is isolated from surface wind-mixing during summer,[3] and usually receives insufficient irradiance (light) for photosynthesis
to occur.

Oxygen dynamics

The deepest portions of the hypolimnion often have lower oxygen concentrations than the surface waters (i.e.,

lake turnover allows mixing of oxic surface waters and anoxic bottom waters.[7]

Notably, anoxic conditions in temperate lakes have the potential to create a positive feedback, whereby anoxia during a given year begets increasingly severe and frequent occurrences of anoxia in future years.[8] Anoxia can lead to release of nutrients from sediment, which contribute to increased phytoplankton growth. Increased phytoplankton growth subsequently increases decomposition, perpetuating hypolimnetic oxygen declines. This positive feedback effect has been termed the Anoxia Begets Anoxia feedback.[8]

Hypolimnetic aeration

In eutrophic lakes where the hypolimnion is anoxic, hypolimnetic aeration may be used to add oxygen to the hypolimnion.[1] Adding oxygen to the system through aeration can be costly because it requires significant amounts of energy.

See also

References

  1. ^
    OCLC 784140625.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link
    )
  2. S2CID 211138964
    .
  3. S2CID 209571196
    .
  4. S2CID 211138964
    .
  5. S2CID 209571196
    .
  6. S2CID 54168543
    .
  7. ISSN 0022-1694
    .
  8. ^
    hdl:10919/118062
    .

External links
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