Photic zone


Photic zone

The photic zone or euphotic zone (Greek 'well lit') is the depth of the water in a lake or ocean, that is exposed to sufficient sunlight for photosynthesis to occur. The depth of the photic zone can be greatly affected by seasonal turbidity.

It extends from the atmosphere-water interface downwards to a depth where light intensity falls to 1% of that at the surface (also called euphotic depth), so its thickness depends on the extent of light attenuation in the water column. Typical euphotic depths vary from only a few centimetres in highly turbid eutrophic lakes, to around 200 metres in the open ocean.

Since the euphotic zone is the only zone of water where primary productivity occurs, an exception being the productivity connected with abyssal hydrothermal vents along mid-oceanic ridges, the depth of the photic zone is generally proportional to the level of primary productivity that occurs in that area of the ocean. About 90% of all marine life lives in this region.

The transparency of the water, which determines the depth of the photic zone, is simply measured with a Secchi disk.


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Look at other dictionaries:

  • photic zone — n. the uppermost layer in a body of water into which daylight penetrates in sufficient amounts to influence living organisms, esp. by permitting photosynthesis …   English World dictionary

  • photic zone — Biol. the upper layer of a body of water delineated by the depth to which enough sunlight can penetrate to permit photosynthesis. [1970 75] * * * ▪ oceanography       surface layer of the ocean that receives sunlight. The uppermost 80 m (260… …   Universalium

  • photic zone — fotinė zona statusas T sritis ekologija ir aplinkotyra apibrėžtis Ežero, tvenkinio, jūros ar vandenyno priekrantės sritis (ežeruose, tvenkiniuose iki 2 m gylio, jūrose iki 200 m gylio), kur prasiskverbia saulės šviesa ir gali vykti fotosintezė.… …   Ekologijos terminų aiškinamasis žodynas

  • photic zone — noun see photic region * * * Biol. the upper layer of a body of water delineated by the depth to which enough sunlight can penetrate to permit photosynthesis. [1970 75] …   Useful english dictionary

  • photic zone — Surface waters penetrated by light; see aphotic zone …   Dictionary of invertebrate zoology

  • photic zone — /ˈfoʊtɪk zoʊn/ (say fohtik zohn) noun → euphotic zone …   Australian English dictionary

  • photic zone — surface waters where there is enough light for photosynthesis …   Dictionary of ichthyology

  • photic zone — noun that part of the near surface body of an ocean or lake that receives enough sunlight for photosynthesis to be possible …   Wiktionary

  • photic zone — layer of the ocean that is penetrated by sunlight …   English contemporary dictionary

  • photic layer — fotinė zona statusas T sritis ekologija ir aplinkotyra apibrėžtis Ežero, tvenkinio, jūros ar vandenyno priekrantės sritis (ežeruose, tvenkiniuose iki 2 m gylio, jūrose iki 200 m gylio), kur prasiskverbia saulės šviesa ir gali vykti fotosintezė.… …   Ekologijos terminų aiškinamasis žodynas


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