Photic zone - Wikipedia Photic zone Aquatic layers Pelagic Photic Epipelagic Aphotic Mesopelagic Bathypelagic Abyssopelagic Hadopelagic Demersal Benthic Stratification Pycnocline Isopycnal Chemocline Halocline Thermocline Thermohaline See also Marine habitats Lake stratification Aquatic ecosystems Wild fisheries This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( January 2017 ) The photic zone, euphotic zone ( Greek for `` well lit '' : εὖ `` well '' + φῶς `` light '' ), or sunlight or ( Sunlit ) zone is the depth of the water in a lake or ocean that is exposed to such intensity of sunlight which designates compensation point, i.e. the intensity of light at which the rate of carbon dioxide uptake, or equivalently, the rate of oxygen production, is equal to the rate of carbon dioxide production, equivalently to the rate of oxygen consumption, reducing thus the net carbon dioxide assimilation to zero. It extends from the surface down to a depth where light intensity falls to one percent of that at the surface, called the euphotic depth. Accordingly, 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 meters in the open ocean. It also varies with seasonal changes in turbidity. Since the photic zone is where almost all of the photosynthesis occurs, the depth of the photic zone is generally proportional to the level of primary production that occurs in that area of the ocean. About 90 % of all marine life lives in the photic zone. A small amount of primary production is generated deep in the abyssal zone around the hydrothermal vents which exist along some mid-oceanic ridges. The zone which extends from the base of the euphotic zone to about 200 metres is sometimes called the disphotic zone. While there is some light, it is insufficient for photosynthesis, or at least insufficient for photosynthesis at a rate greater than respiration. The euphotic zone together with the disphotic zone coincides with the epipelagic zone. The bottommost zone, below the euphotic zone, is called the aphotic zone. Most deep ocean waters belong to this zone. The transparency of the water, which determines the depth of the photic zone, is measured simply with a Secchi disk. It may also be measured with a photometer lowered into the water. See also Electromagnetic absorption by water Epipelagic fish References Jump up ^ Photic zone Encyclopædia Britannica Online. 14 August 2009. 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Question: where does primary productivity occur outside of the photic zone
Answer: deep in the abyssal zone around the hydrothermal vents which exist along some mid-oceanic ridges