Mesopelagic zone - wikipedia Mesopelagic 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 Pelagic zones The mesopelagic ( Greek μέσον, middle ) ( also known as the middle pelagic or twilight zone ) is that part of the pelagic zone that extends from a depth of 200 to 1000 metres ( ~ 660 to 3300 feet ) below the ocean surface. It lies between the photic epipelagic above and the aphotic bathypelagic below, where there is no light at all. Contents 1 Physical conditions 2 Ecology 2.1 Climate change 3 References 4 See also Physical conditions Although the temperature varies less at any one height than the epipelagic, the mesopelagic is the location of the thermocline, and in warmer regions of the world, the temperature varies from over 20 ° C ( 68 ° F ) at the top to around 4 ° C ( 39 ° F ) at the boundary with the bathyal zone. Water generally moves slowly in the mesopelagic with a residency time of about a century, though a variety of animals move vertically through the zone on a daily basis and various debris sink down in relatively short time frames. The region was initially discovered by American researchers during World War II in 1942 during anti-submarine research with sonar. Sonar at the time could not penetrate below this depth due to the large number of creatures obstructing sound waves. Ecology Although some light penetrates the mesopelagic zone, it is insufficient for photosynthesis. The general types of life forms found are daytime visiting herbivores, detritivores feeding on dead organisms and fecal pellets, and carnivores feeding on the former types. Algae do not reside inside the mesopelagic layer, due to lack of light. Examples of animals in the mesopelagic zone are bristlemouth, swordfish, squid, wolf eels, cuttlefish and other semi-deepsea creatures. The bristlemouth is the Earth 's most abundant vertebrate, numbering in the hundreds of trillions to quadrillions. The small amount of sunlight is sufficient for animals, such as the chain catshark, to be fluorescent. A 2015 study found that the zone 's biomass is up to 10 times greater than earlier estimates, totaling 10 billion tons and representing some 90 percent of the planet 's fish biomass, some 100 times that of the annual seafood catch and 200 times that of the world 's 24 billion chickens. Commercial fisherman have found the biomass viable for fish farming meal, oil and silage. In 2002, the UN Food and Agriculture Organization discussed in a report that the mesopelagic zone has biomass viable for fish - meal and fish - oil industry. Climate Change The quantity of mesopelagic life is large enough to play a significant role in global carbon cycling. As the fish participate in the food chain, they acquire carbon rendered from carbon dioxide absorbed by surface waters. Upon death, they transport that carbon into the sea bottom or back upon coastal shores. As of 2015 the revised estimates of mesopelagic life had yet to be incorporated into climate models. Per year, it is estimated to cycle between 5 billion and 12 billion tonnes of CO2 from the atmosphere through the ocean region. References Jump up ^ Trujillo, Alan P. ; Thurman, Harold V. ( 2010 ). Essentials of Oceanography ( 10th ed. ). Prentice Hall. pp. 363 -- 366. ^ Jump up to : Hogan, Michael C. `` Mesopelagic zone ''. The Encyclopedia or Earth. Retrieved 17 September 2013. ^ Jump up to : `` The mesopelagic : Cinderella of the oceans ''. The Economist. Retrieved 2017 - 04 - 23. Jump up ^ Broad, William J. ( June 29, 2015 ). `` An Ocean Mystery in the Trillions ''. The New York Times. Retrieved August 2015. Check date values in : access - date = ( help ) ^ Jump up to : BROAD, WILLIAM J. ( June 29, 2015 ). `` Dark Region of Ocean May Shed Light on Climate Change and Other Issues ''. New York Times. Retrieved 2017 - 04 - 23. See also Mesopelagic fish Physical oceanography Waves Airy wave theory Ballantine scale Benjamin -- Feir instability Boussinesq approximation Breaking wave Clapotis Cnoidal wave Cross sea Dispersion Edge wave Equatorial waves Fetch Gravity wave Green 's law Infragravity wave Internal wave Iribarren number Kelvin wave Kinematic wave Longshore drift Luke 's variational principle Mild - slope equation Radiation stress Rogue wave Rossby wave Rossby - gravity waves Sea state Seiche Significant wave height Soliton Stokes boundary layer Stokes drift Stokes wave Swell Trochoidal wave Tsunami megatsunami Undertow Ursell number Wave action Wave base Wave height Wave power Wave radar Wave setup Wave shoaling Wave turbulence Wave -- current interaction Waves and shallow water one - dimensional Saint - Venant equations shallow water equations Wind wave model Circulation Atmospheric circulation Baroclinity Boundary current Coriolis force Coriolis -- Stokes force Craik -- Leibovich vortex force Downwelling Eddy Ekman layer Ekman spiral Ekman transport El Niño -- Southern Oscillation General circulation model Geostrophic current Global Ocean Data Analysis Project Gulf Stream Halothermal circulation Humboldt Current Hydrothermal circulation Langmuir circulation Longshore drift Loop Current Modular Ocean Model Ocean dynamics Ocean gyre Princeton Ocean Model Rip current Subsurface currents Sverdrup balance Thermohaline circulation shutdown Upwelling Whirlpool World Ocean Circulation Experiment Tides Amphidromic point Earth tide Head of tide Internal tide Lunitidal interval Perigean spring tide Rip tide Rule of twelfths Slack water Tidal bore Tidal force Tidal power Tidal race Tidal range Tidal resonance Tide gauge Tideline Landforms Abyssal fan Abyssal plain Atoll Bathymetric chart Coastal geography Cold seep Continental margin Continental rise Continental shelf Contourite Guyot Hydrography Oceanic basin Oceanic plateau Oceanic trench Passive margin Seabed Seamount Submarine canyon Submarine volcano Plate tectonics Convergent boundary Divergent boundary Fracture zone Hydrothermal vent Marine geology Mid-ocean ridge Mohorovičić discontinuity Vine -- Matthews -- Morley hypothesis Oceanic crust Outer trench swell Ridge push Seafloor spreading Slab pull Slab suction Slab window Subduction Transform fault Volcanic arc Ocean zones Benthic Deep ocean water Deep sea Littoral Mesopelagic Oceanic Pelagic Photic Surf Swash Sea level Deep - ocean Assessment and Reporting of Tsunamis Future sea level Global Sea Level Observing System North West Shelf Operational Oceanographic System Sea - level curve Sea level rise World Geodetic System Acoustics Deep scattering layer Hydroacoustics Ocean acoustic tomography Sofar bomb SOFAR channel Underwater acoustics Satellites Jason - 1 Jason - 2 ( Ocean Surface Topography Mission ) Jason - 3 Related Argo Benthic lander Color of water DSV Alvin Marginal sea Marine energy Marine pollution Mooring National Oceanographic Data Center Ocean Ocean exploration Ocean observations Ocean reanalysis Ocean surface topography Ocean thermal energy conversion Oceanography Pelagic sediment Sea surface microlayer Sea surface temperature Seawater Science On a Sphere Thermocline Underwater glider Water column World Ocean Atlas Commons Retrieved from `` https://en.wikipedia.org/w/index.php?title=Mesopelagic_zone&oldid=814919959 '' Categories : Aquatic biomes Oceanography Hidden categories : CS1 errors : dates Talk Contents About Wikipedia Español Gaeilge 한국어 Italiano Português Suomi Svenska 中文 Edit links This page was last edited on 11 December 2017, at 18 : 18. 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Question: how deep is the twilight zone in the ocean
Answer: 200 to 1000 metres (~660 to 3300 feet)[1] below the ocean surface