Deep sea
{{Short description|Lowest layer in the ocean}}
{{For|the films|Deep Sea 3D|Deep Sea (film)}}
File:Schematic_representation_of_pelagic_and_benthic_zones.jpg
The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of {{cvt|200|m|ft}} or the point of transition from continental shelves to continental slopes.{{Cite book |last=Tyler |first=P. A. |title=In Ecosystems of the World 28, Ecosystems of the Deep Sea |publisher=Elsevier |year=2003 |edition= |location=Amsterdam |pages=1–3}}{{Cite web |title=What is the "deep" ocean? : Ocean Exploration Facts: NOAA Office of Ocean Exploration and Research |url=https://oceanexplorer.noaa.gov/facts/deep-ocean.html |access-date=2022-09-29 |website=oceanexplorer.noaa.gov |language=en-US}} Conditions within the deep sea are a combination of low temperatures, darkness, and high pressure.{{Cite journal |last=Paulus |first=Eva |date=2021 |title=Shedding Light on Deep-Sea Biodiversity—A Highly Vulnerable Habitat in the Face of Anthropogenic Change |journal=Frontiers in Marine Science |volume=8 |doi=10.3389/fmars.2021.667048 |issn=2296-7745|doi-access=free }} The deep sea is considered the least explored Earth biome as the extreme conditions make the environment difficult to access and explore.{{Cite journal |last1=Danovaro |first1=Roberto |last2=Corinaldesi |first2=Cinzia |last3=Dell’Anno |first3=Antonio |last4=Snelgrove |first4=Paul V. R. |date=2017-06-05 |title=The deep-sea under global change |journal=Current Biology |language=en |volume=27 |issue=11 |pages=R461–R465 |doi=10.1016/j.cub.2017.02.046 |pmid=28586679 |s2cid=20785268 |issn=0960-9822|doi-access=free }}
Organisms living within the deep sea have a variety of adaptations to survive in these conditions.{{Cite journal |last1=Brown |first1=Alastair |last2=Thatje |first2=Sven |date=2013 |title=Explaining bathymetric diversity patterns in marine benthic invertebrates and demersal fishes: physiological contributions to adaptation of life at depth |journal=Biological Reviews |language=en |volume=89 |issue=2 |pages=406–426 |doi=10.1111/brv.12061 |issn=1464-7931 |pmc=4158864 |pmid=24118851}} Organisms can survive in the deep sea through a number of feeding methods including scavenging, predation and filtration, with a number of organisms surviving by feeding on marine snow.{{Cite journal |last1=Higgs |first1=Nicholas D. |last2=Gates |first2=Andrew R. |last3=Jones |first3=Daniel O. B. |date=2014-05-07 |title=Fish Food in the Deep Sea: Revisiting the Role of Large Food-Falls |journal=PLOS ONE |volume=9 |issue=5 |pages=e96016 |doi=10.1371/journal.pone.0096016 |issn=1932-6203 |pmc=4013046 |pmid=24804731|bibcode=2014PLoSO...996016H |doi-access=free }} Marine snow is organic material that has fallen from upper waters into the deep sea.{{Cite web |last=US Department of Commerce |first=National Oceanic and Atmospheric Administration |title=What is marine snow? |url=https://oceanservice.noaa.gov/facts/marinesnow.html |access-date=2022-09-29 |website=oceanservice.noaa.gov |language=EN-US}}
In 1960, the bathyscaphe Trieste descended to the bottom of the Mariana Trench near Guam, at {{cvt|10911|m|ft mi}}, the deepest known spot in any ocean. If Mount Everest ({{cvt|8848|m|ft mi|disp=or}}) were submerged there, its peak would be more than {{cvt|2|km|mi}} beneath the surface. After the Trieste was retired, the Japanese remote-operated vehicle (ROV) Kaikō was the only vessel capable of reaching this depth until it was lost at sea in 2003.{{Cite web|last=Horstman|first=Mark|date=2003-07-09|title=Hope floats for lost deep-sea explorer|url=https://www.abc.net.au/science/articles/2003/07/09/897958.htm|url-status=live|access-date=2021-05-07|website=www.abc.net.au|language=en-AU|archive-url=https://web.archive.org/web/20100927060331/http://www.abc.net.au:80/science/articles/2003/07/09/897958.htm |archive-date=2010-09-27 }} In May and June 2009, the hybrid-ROV Nereus returned to the Challenger Deep for a series of three dives to depths exceeding {{cvt|10,900|m|ft mi}}.
Environmental characteristics
= Light =
Natural light does not penetrate the deep ocean, with the exception of the upper parts of the mesopelagic. Since photosynthesis is not possible, plants and phytoplankton cannot live in this zone, and as these are the primary producers of almost all of earth's ecosystems, life in this area of the ocean must depend on energy sources from elsewhere. Except for the areas close to the hydrothermal vents, this energy comes from organic material drifting down from the photic zone. The sinking organic material is composed of algal particulates, detritus, and other forms of biological waste, which is collectively referred to as marine snow.
= Pressure =
Because pressure in the ocean increases by about 1 atmosphere for every 10 meters of depth, the amount of pressure experienced by many marine organisms is extreme. Until recent years, the scientific community lacked detailed information about the effects of pressure on most deep sea organisms because the specimens encountered arrived at the surface dead or dying and weren't observable at the pressures at which they lived. With the advent of traps that incorporate a special pressure-maintaining chamber, undamaged larger metazoan animals have been retrieved from the deep sea in good condition.{{citation needed|date=May 2021}}
= Salinity =
Salinity is remarkably constant throughout the deep sea, at about 35 parts per thousand.Claus Detlefsen. "[http://ing.dk/artikel/spoerg-scientariet-noget-om-marianergraven-del-2-163895 About the Marianas]" (in Danish) Ingeniøren / Geological Survey of Denmark and Greenland, 2 November 2013. Accessed: 2 November 2013. There are some minor differences in salinity, but none that are ecologically significant, except in largely landlocked seas like the Mediterranean and Red Seas{{citation needed|date=December 2023}}.
= Temperature =
The two areas of greatest temperature gradient in the oceans are the transition zone between the surface waters and the deep waters, the thermocline, and the transition between the deep-sea floor and the hot water flows at the hydrothermal vents. Thermoclines vary in thickness from a few hundred meters to nearly a thousand meters. Below the thermocline, the water mass of the deep ocean is cold and far more homogeneous. Thermoclines are strongest in the tropics, where the temperature of the epipelagic zone is usually above {{convert|20|°C|°F|abbr=on}}. From the base of the epipelagic, the temperature drops over several hundred meters to 5–6 °C at 1,000 meters (41–43 °F at 3,300 ft). It continues to decrease to the bottom, but the rate is much slower. The cold water stems from sinking heavy surface water in the polar regions.
At any given depth, the temperature is practically unvarying over long periods of time, without seasonal changes and with very little interannual variability. No other habitat on earth has such a constant temperature.{{Cite web|last=MarineBio|date=2018-06-17|title=The Deep Sea|url=https://marinebio.org/oceans/deep-sea/|access-date=2020-08-07|website=MarineBio Conservation Society|language=en-US}}
In hydrothermal vents the temperature of the water as it emerges from the "black smoker" chimneys may be as high as {{convert|400|°C|°F|abbr=on}}, being kept from boiling by the high hydrostatic pressure – thus being superheated water. The temperature may back down to {{convert|2|to|4|C|F}} within a few meters.Nybakken, James W. Marine Biology: An Ecological Approach. Fifth Edition. Benjamin Cummings, 2001. pp. 136–141.
Biology
{{Main|Deep-sea community}}
Regions below the epipelagic are divided into further zones, beginning with the bathyal zone (also considered the continental slope) which spans from {{convert|200|to|3000|m|ft|sp=us}}{{cite journal |last1=Levin |first1=Lisa A. |last2=Dayton |first2=Paul K. |title=Ecological theory and continental margins: where shallow meets deep |journal=Trends in Ecology & Evolution |date=1 November 2009 |volume=24 |issue=11 |pages=606–617 |doi=10.1016/j.tree.2009.04.012 |pmid=19692143 |url=https://www.sciencedirect.com/science/article/pii/S0169534709001992 |access-date=29 September 2022 |language=en |issn=0169-5347|url-access=subscription }} below sea level and is essentially transitional, containing elements from both the shelf above and the abyss below.{{cite book |last1=Gage |first1=John D. |last2=Tyler |first2=Paul A. |title=Deep-Sea Biology: A Natural History of Organisms at the Deep-Sea Floor |date=18 April 1991 |publisher=Cambridge University Press |isbn=978-0-521-33431-0 |url=https://books.google.com/books?id=vqgfH9DXXNAC&q=zone&pg=PR11 |access-date=29 September 2022 |language=en}} Below this zone, the deep sea consists of the abyssal zone (ocean depth between {{convert|3|-|6|km|mi|abbr=on|disp=semicolon}}){{cite journal |last1=Smith |first1=Craig R. |last2=De Leo |first2=Fabio C. |last3=Bernardino |first3=Angelo F. |last4=Sweetman |first4=Andrew K. |last5=Arbizu |first5=Pedro Martinez |title=Abyssal food limitation, ecosystem structure and climate change |journal=Trends in Ecology & Evolution |date=1 September 2008 |volume=23 |issue=9 |pages=518–528 |doi=10.1016/j.tree.2008.05.002 |pmid=18584909 |url=https://www.sciencedirect.com/science/article/pii/S0169534708001900 |access-date=29 September 2022 |language=en |issn=0169-5347|url-access=subscription }} and the hadal zone ({{convert|6|-|11|km|mi|abbr=on|disp=semicolon}}).{{cite journal |last1=Jamieson |first1=Alan J. |last2=Fujii |first2=Toyonobu |last3=Mayor |first3=Daniel J. |last4=Solan |first4=Martin |last5=Priede |first5=Imants G. |title=Hadal trenches: the ecology of the deepest places on Earth |journal=Trends in Ecology & Evolution |date=1 March 2010 |volume=25 |issue=3 |pages=190–197 |doi=10.1016/j.tree.2009.09.009 |pmid=19846236 |url=https://www.sciencedirect.com/science/article/pii/S0169534709002997 |access-date=29 September 2022 |language=en |issn=0169-5347|url-access=subscription }}{{cite journal |last1=Jamieson |first1=Alan J. |last2=Stewart |first2=Heather A. |last3=Weston |first3=Johanna N. J. |last4=Lahey |first4=Patrick |last5=Vescovo |first5=Victor L. |title=Hadal Biodiversity, Habitats and Potential Chemosynthesis in the Java Trench, Eastern Indian Ocean |journal=Frontiers in Marine Science |date=2022 |volume=9 |doi=10.3389/fmars.2022.856992 |doi-access=free }} Food consists of falling organic matter known as 'marine snow' and carcasses derived from the productive zone above, and is scarce both in terms of spatial and temporal distribution.{{Cite journal |last1=Robison |first1=Bruce H. |last2=Reisenbichler |first2=Kim R. |last3=Sherlock |first3=Rob E. |date=2005-06-10 |title=Giant Larvacean Houses: Rapid Carbon Transport to the Deep Sea Floor |url=https://www.science.org/doi/10.1126/science.1109104 |journal=Science |language=en |volume=308 |issue=5728 |pages=1609–1611 |doi=10.1126/science.1109104 |pmid=15947183 |bibcode=2005Sci...308.1609R |s2cid=730130 |issn=0036-8075|url-access=subscription }}
Instead of relying on gas for their buoyancy, many deep-sea species have jelly-like flesh consisting mostly of glycosaminoglycans, which provides them with very low density. It is also common among deep water squid to combine the gelatinous tissue with a flotation chamber filled with a coelomic fluid made up of the metabolic waste product ammonium chloride, which is lighter than the surrounding water.{{Citation needed|date=December 2022}}
The midwater fish have special adaptations to cope with these conditions—they are small, usually being under {{convert|25|cm|in|0}}; they have slow metabolisms and unspecialized diets, preferring to sit and wait for food rather than waste energy searching for it. They have elongated bodies with weak, watery muscles and skeletal structures. They often have extendable, hinged jaws with recurved teeth. Because of the sparse distribution and lack of light, finding a partner with which to breed is difficult, and many organisms are hermaphroditic.{{Citation needed|date=December 2022}}
Because light is so scarce, fish often have larger than normal, tubular eyes with only rod cells.{{cite journal |last1=Lupše |first1=Nik |last2=Cortesi |first2=Fabio |last3=Freese |first3=Marko |last4=Marohn |first4=Lasse |last5=Pohlmann |first5=Jan-Dag |last6=Wysujack |first6=Klaus |last7=Hanel |first7=Reinhold |last8=Musilova |first8=Zuzana |title=Visual Gene Expression Reveals a cone-to-rod Developmental Progression in Deep-Sea Fishes |journal=Molecular Biology and Evolution |date=9 December 2021 |volume=38 |issue=12 |pages=5664–5677 |doi=10.1093/molbev/msab281 |pmid=34562090 |pmc=8662630 |url=https://doi.org/10.1093/molbev/msab281 |access-date=29 September 2022}}{{Cite journal |last1=Warrant |first1=Eric J. |last2=Locket |first2=N. Adam |date=August 2004 |title=Vision in the deep sea |url=https://www.cambridge.org/core/journals/biological-reviews/article/abs/vision-in-the-deep-sea/3A8B971B023A9FDC48E4B863B3B801FF |journal=Biological Reviews |language=en |volume=79 |issue=3 |pages=671–712 |doi=10.1017/S1464793103006420 |pmid=15366767 |s2cid=34907805 |issn=1469-185X|url-access=subscription }} Their upward field of vision allows them to seek out the silhouette of possible prey.{{cite book |last1=Collin |first1=Shaun P. |last2=Chapuis |first2=Lucille |last3=Michiels |first3=Nico K. |title=Marine Extremes |publisher=Routledge |isbn=9780429491023 |url=https://www.taylorfrancis.com/chapters/edit/10.4324/9780429491023-12/impacts-extreme-depth-life-deep-sea-shaun-collin-lucille-chapuis-nico-michiels |access-date=29 September 2022 |chapter=Impacts of (extreme) depth on life in the deep-sea|year=2019 |pages=197–216 |doi=10.4324/9780429491023-12 |s2cid=133939260 }} Prey fish however also have adaptations to cope with predation. These adaptations are mainly concerned with reduction of silhouettes, a form of camouflage. The two main methods by which this is achieved are reduction in the area of their shadow by lateral compression of the body,{{cite journal |last1=Hoving |first1=Henk‐Jan T. |last2=Freitas |first2=Rui |title=Pelagic observations of the midwater scorpionfish Ectreposebastes imus (Setarchidae) suggests a role in trophic coupling between deep‐sea habitats |url=https://onlinelibrary.wiley.com/doi/10.1111/jfb.14944 |journal=Journal of Fish Biology |date=February 2022 |volume=100 |issue=2 |pages=586–589 |doi=10.1111/jfb.14944 |pmid=34751439 |s2cid=243863469 |access-date=29 September 2022}} and counter illumination via bioluminescence.{{cite journal |last1=Davis |first1=Alexander L. |last2=Sutton |first2=Tracey T. |last3=Kier |first3=William M. |last4=Johnsen |first4=Sönke |title=Evidence that eye-facing photophores serve as a reference for counterillumination in an order of deep-sea fishes |journal=Proceedings of the Royal Society B: Biological Sciences |date=10 June 2020 |volume=287 |issue=1928 |pages=20192918 |doi=10.1098/rspb.2019.2918 |pmid=32517614 |pmc=7341941 }} This is achieved by production of light from ventral photophores, which tend to produce such light intensity to render the underside of the fish of similar appearance to the background light. For more sensitive vision in low light, some fish have a retroreflector behind the retina.{{cite journal |last1=Palmer |first1=Benjamin A. |last2=Gur |first2=Dvir |last3=Weiner |first3=Steve |last4=Addadi |first4=Lia |last5=Oron |first5=Dan |title=The Organic Crystalline Materials of Vision: Structure-Function Considerations from the Nanometer to the Millimeter Scale |journal=Advanced Materials |date=October 2018 |volume=30 |issue=41 |pages=1800006 |doi=10.1002/adma.201800006 |pmid=29888511 |s2cid=47005095 |url=https://onlinelibrary.wiley.com/doi/full/10.1002/adma.201800006 |access-date=29 September 2022 |language=en|url-access=subscription }} Flashlight fish have this plus photophores, which combination they use to detect eyeshine in other fish (see tapetum lucidum).{{Cite journal |last1=Hellinger |first1=Jens |last2=Jägers |first2=Peter |last3=Donner |first3=Marcel |last4=Sutt |first4=Franziska |last5=Mark |first5=Melanie D. |last6=Senen |first6=Budiono |last7=Tollrian |first7=Ralph |last8=Herlitze |first8=Stefan |date=2017-02-08 |editor-last=De |editor-first=Abhijit |title=The Flashlight Fish Anomalops katoptron Uses Bioluminescent Light to Detect Prey in the Dark |journal=PLOS ONE |language=en |volume=12 |issue=2 |pages=e0170489 |doi=10.1371/journal.pone.0170489 |pmid=28178297 |pmc=5298212 |bibcode=2017PLoSO..1270489H |issn=1932-6203|doi-access=free }}{{Cite journal |last1=Cavallaro |first1=Mauro |last2=Guerrera |first2=Maria Cristina |last3=Abbate |first3=Francesco |last4=Levanti |first4=Maria Beatrice |last5=Laurà |first5=Rosaria |last6=Ammendolia |first6=Giovanni |last7=Malara |first7=Danilo |last8=Stipa |first8=Maria Giulia |last9=Battaglia |first9=Pietro |date=October 2021 |title=Morphological, ultrastructural and immunohistochemical study on the skin ventral photophores of Diaphus holti Tåning, 1918 (Family: Myctophidae) |url=https://onlinelibrary.wiley.com/doi/10.1111/azo.12348 |journal=Acta Zoologica |language=en |volume=102 |issue=4 |pages=405–411 |doi=10.1111/azo.12348 |s2cid=225368866 |issn=0001-7272|url-access=subscription }}
Organisms in the deep sea are almost entirely reliant upon sinking living and dead organic matter which falls at approximately 100 meters per day.{{cite web|url=http://www.whoi.edu/oceanus/viewArticle.do?id=2387&archives=true|title=Marine Snow and Fecal Pellets|website=Oceanus Magazine}} In addition, only about 1 to 3% of the production from the surface reaches the seabed, mostly in the form of marine snow. This ends up accumulating on the benthic floor, around 1 cm every 1,000 years. Larger food falls, such as whale carcasses, also occur and studies have shown that these may happen more often than currently believed. There are many scavengers that feed primarily or entirely upon large food falls and the distance between whale carcasses is estimated to only be 8 kilometers.R. N. Gibson, Harold (CON) Barnes, R. J. A. Atkinson, Oceanography and Marine Biology, An Annual Review. 2007. Volume 41. Published by CRC Press, 2004
{{ISBN|0-415-25463-9}}, {{ISBN|978-0-415-25463-2}} In addition, there are a number of filter feeders that feed upon organic particles using tentacles, such as Freyella elegans.{{cite web|url=http://www.nhm.ac.uk/nature-online/earth/oceans/deep-ocean/session3/index.html|title=Discover - Natural History Museum|website=www.nhm.ac.uk}}
Marine bacteriophages play an important role in cycling nutrients in deep sea sediments. They are extremely abundant (between 5×1012 and 1×1013 phages per square meter) in sediments around the world.{{cite journal|last=Danovaro|first=Roberto |author2=Antonio Dell'Anno |author3=Cinzia Corinaldesi |author4=Mirko Magagnini |author5=Rachel Noble |author6=Christian Tamburini |author7=Markus Weinbauer |date=2008-08-28|title=Major viral impact on the functioning of benthic deep-sea ecosystems|journal=Nature|volume=454|pages=1084–1087|doi=10.1038/nature07268|pmid=18756250|issue=7208|bibcode=2008Natur.454.1084D |s2cid=4331430 }}
Despite being so isolated deep sea organisms have still been harmed by human interaction with the oceans. The London Convention{{cite web |url=http://www.imo.org/en/OurWork/Environment/LCLP/Pages/default.aspx |title=London Convention |publisher=International Maritime Organization |access-date=24 March 2020 |archive-date=3 March 2019 |archive-url=https://web.archive.org/web/20190303180237/http://www.imo.org/en/OurWork/Environment/LCLP/Pages/default.aspx |url-status=dead }} aims to protect the marine environment from dumping of wastes such as sewage sludge{{cite journal |last1=Snelgrove |first1=Paul |last2=Grassle |first2=Fred |title=What of the deep sea's future diversity? |journal=Oceanus |date=1995-01-01 |volume=38 |issue=2 |url=https://www.questia.com/read/1G1-18018331/what-of-the-deep-sea-s-future-diversity |access-date=24 March 2020 |archive-date=2020-07-29 |archive-url=https://web.archive.org/web/20200729031459/https://www.questia.com/read/1G1-18018331/what-of-the-deep-sea-s-future-diversity |url-status=dead }} and radioactive waste. A study found that at one region there had been a decrease in deep sea coral from 2007 to 2011, with the decrease being attributed to global warming and ocean acidification, and biodiversity estimated as being at the lowest levels in 58 years.{{cite journal |last1=Zimmerman |first1=Alexander N. |last2=Johnson |first2=Claudia C. |last3=Bussberg |first3=Nicholas W. |last4=Dalkilic |first4=Mehmet M. |title=Stability and decline in deep-sea coral biodiversity, Gulf of Mexico and US West Atlantic |journal=Coral Reefs |date=April 2020 |volume=39 |issue=2 |pages=345–359 |doi=10.1007/s00338-020-01896-9 |s2cid=210975434}} Ocean acidification is particularly harmful to deep sea corals because they are made of aragonite, an easily soluble carbonate, and because they are particularly slow growing and will take years to recover.{{cite journal|last=Ruttimann|first=Jacqueline|date=2006-08-31|title=Oceanography: sick seas|journal=Nature|volume=442|issue=7106|pages=978–80|doi=10.1038/442978a|pmid=16943816|bibcode=2006Natur.442..978R|s2cid=4332965|doi-access=free}} Deep sea trawling is also harming the biodiversity by destroying deep sea habitats which can take years to form.{{cite journal|last=Koslow|first=Tony|date=2011-11-20|title=The silent deep: the discovery, ecology & conservation of the deep sea|journal=Pacific Ecologist|volume=20}} Another human activity that has altered deep sea biology is mining. One study found that at one mining site fish populations had decreased at six months and at three years, and that after twenty six years populations had returned to the same levels as prior to the disturbance.{{cite journal |last1=Drazen |first1=Jeffery |last2=Leitner |first2=Astrid |last3=Morningstar |first3=Sage |last4=Marcon |first4=Yann |last5=Greinert |first5=Jens |last6=Purser |first6=Auntun |title=Observations of deep-sea fishes and mobile scavengers from the abyssal DISCOL experimental mining area |journal= Biogeosciences|date=2019-01-01 |volume=16 |issue=16|pages=3133–3146 |doi=10.5194/bg-16-3133-2019|bibcode=2019BGeo...16.3133D |id={{ProQuest|2276806480}} |doi-access=free }}
= Chemosynthesis =
There are a number of species that do not primarily rely upon dissolved organic matter for their food. These species and communities are found at hydrothermal vents at sea-floor spreading zones.{{Cite book |url=https://press.princeton.edu/books/paperback/9780691049298/the-ecology-of-deep-sea-hydrothermal-vents |title=The Ecology of Deep-Sea Hydrothermal Vents |date=2000-03-26 |isbn=978-0-691-04929-8 |language=en|last1=Dover |first1=Cindy Van |publisher=Princeton University Press }}{{Cite journal |last1=Martin |first1=William |last2=Baross |first2=John |last3=Kelley |first3=Deborah |last4=Russell |first4=Michael J. |date=November 2008 |title=Hydrothermal vents and the origin of life |url=https://www.nature.com/articles/nrmicro1991 |journal=Nature Reviews Microbiology |language=en |volume=6 |issue=11 |pages=805–814 |doi=10.1038/nrmicro1991 |pmid=18820700 |s2cid=1709272 |issn=1740-1534|url-access=subscription }} One example is the symbiotic relationship between the tube worm Riftia and chemosynthetic bacteria.{{Cite journal |last=Cavanaugh |first=F. J. Stewart and C. M. |title=Symbiosis of Thioautotrophic Bacteria with Riftia pachyptila {{!}} EndNote Click |url=https://link.springer.com/chapter/10.1007/3-540-28221-1_10 |access-date=2022-09-29 |journal=Progress in Molecular and Subcellular Biology |year=2006 |volume=41 |pages=197–225 |language=en |doi=10.1007/3-540-28221-1_10|pmid=16623395 |url-access=subscription }} It is this chemosynthesis that supports the complex communities that can be found around hydrothermal vents. These complex communities are one of the few ecosystems on the planet that do not rely upon sunlight for their supply of energy.HW Jannasch. 1985. The Chemosynthetic Support of Life and the Microbial Diversity at Deep-Sea Hydrothermal Vents. Proceedings of the Royal Society of London. Series B, Biological Sciences, Vol. 225, No. 1240 (Sep. 23, 1985), pp. 277-297
= Adaptation to hydrostatic pressure =
Deep-sea fish have different adaptations in their proteins, anatomical structures, and metabolic systems to survive in the Deep sea, where the inhabitants have to withstand great amount of hydrostatic pressure. While other factors like food availability and predator avoidance are important, the deep-sea organisms must have the ability to maintain well-regulated metabolic system in the face of high pressures.{{Citation|title=Chapter Twelve. Adaptations to the Deep Sea|date=1984-12-31|url=http://dx.doi.org/10.1515/9781400855414.450|work=Biochemical Adaptation|pages=450–495|publisher=Princeton University Press|doi=10.1515/9781400855414.450|isbn=978-1-4008-5541-4|access-date=2020-11-02|url-access=subscription}} In order to adjust for the extreme environment, these organisms have developed unique characteristics.
Proteins are affected greatly by the elevated hydrostatic pressure, as they undergo changes in water organization during hydration and dehydration reactions of the binding events. This is due to the fact that most enzyme-ligand interactions form through charged or polar non-charge interactions. Because hydrostatic pressure affects both protein folding and assembly and enzymatic activity, the deep sea species must undergo physiological and structural adaptations to preserve protein functionality against pressure.{{Cite journal|last1=Wang|first1=Kun|last2=Shen|first2=Yanjun|last3=Yang|first3=Yongzhi|last4=Gan|first4=Xiaoni|last5=Liu|first5=Guichun|last6=Hu|first6=Kuang|last7=Li|first7=Yongxin|last8=Gao|first8=Zhaoming|last9=Zhu|first9=Li|last10=Yan|first10=Guoyong|last11=He|first11=Lisheng|date=May 2019|title=Morphology and genome of a snailfish from the Mariana Trench provide insights into deep-sea adaptation|journal=Nature Ecology & Evolution|language=en|volume=3|issue=5|pages=823–833|doi=10.1038/s41559-019-0864-8|pmid=30988486|issn=2397-334X|doi-access=free}}
Actin is a protein that is essential for different cellular functions. The α-actin serves as a main component for muscle fiber, and it is highly conserved across numerous different species. Some Deep-sea fish developed pressure tolerance through the change in mechanism of their α-actin. In some species that live in depths greater than {{convert|5|km|mi|abbr=on}}, C.armatus and C.yaquinae have specific substitutions on the active sites of α-Actin, which serves as the main component of muscle fiber.{{Cite journal|last1=Wakai|first1=Nobuhiko|last2=Takemura|first2=Kazuhiro|last3=Morita|first3=Takami|last4=Kitao|first4=Akio|date=2014-01-20|title=Mechanism of Deep-Sea Fish α-Actin Pressure Tolerance Investigated by Molecular Dynamics Simulations|journal=PLOS ONE|language=en|volume=9|issue=1|pages=e85852|doi=10.1371/journal.pone.0085852|issn=1932-6203|pmc=3896411|pmid=24465747|bibcode=2014PLoSO...985852W|doi-access=free}} These specific substitutions, Q137K and V54A from C.armatus or I67P from C.yaquinae are predicted to have importance in pressure tolerance. Substitution in the active sites of actin result in significant changes in the salt bridge patterns of the protein, which allows for better stabilization in ATP binding and sub unit arrangement, confirmed by the free energy analysis and molecular dynamics simulation.{{Cite journal|last1=Hata|first1=Hiroaki|last2=Nishiyama|first2=Masayoshi|last3=Kitao|first3=Akio|date=2020-02-01|title=Molecular dynamics simulation of proteins under high pressure: Structure, function and thermodynamics|url=http://www.sciencedirect.com/science/article/pii/S0304416519301758|journal=Biochimica et Biophysica Acta (BBA) - General Subjects|series=Novel measurement techniques for visualizing 'live' protein molecules|language=en|volume=1864|issue=2|pages=129395|doi=10.1016/j.bbagen.2019.07.004|pmid=31302180|s2cid=196613044 |issn=0304-4165|url-access=subscription}} It was found that deep sea fish have more salt bridges in their actins compared to fish inhabiting the upper zones of the sea.
In relations to protein substitution, specific osmolytes were found to be abundant in deep sea fish under high hydrostatic pressure. For certain chondrichthyans, it was found that Trimethylamine N-oxide (TMAO) increased with depth, replacing other osmolytes and urea.{{Cite journal|last1=Yancey|first1=Paul H.|last2=Speers-Roesch|first2=Ben|last3=Atchinson|first3=Sheila|last4=Reist|first4=James D.|last5=Majewski|first5=Andrew R.|last6=Treberg|first6=Jason R.|date=2017-11-27|title=Osmolyte Adjustments as a Pressure Adaptation in Deep-Sea Chondrichthyan Fishes: An Intraspecific Test in Arctic Skates (Amblyraja hyperborea) along a Depth Gradient|url=https://www.journals.uchicago.edu/doi/10.1086/696157|journal=Physiological and Biochemical Zoology|volume=91|issue=2|pages=788–796|doi=10.1086/696157|pmid=29315031|s2cid=26847773|issn=1522-2152|url-access=subscription}} Due to the ability of TMAO being able to protect proteins from high hydrostatic pressure destabilizing proteins, the osmolyte adjustment serves are an important adaptation for deep sea fish to withstand high hydrostatic pressure.
Deep-sea organisms possess molecular adaptations to survive and thrive in the deep oceans. Mariana hadal snailfish developed modification in the Osteocalcin(burlap) gene, where premature termination of the gene was found. Osteocalcin gene regulates bone development and tissue mineralization, and the frameshift mutation seems to have resulted in the open skull and cartilage-based bone formation. Due to high hydrostatic pressure in the deep sea, closed skulls that organisms living on the surface develop cannot withstand the enforcing stress. Similarly, common bone developments seen in surface vertebrates cannot maintain their structural integrity under constant high pressure.
Exploration
{{Main|Deep-sea exploration}}
It has been suggested that more is known about the Moon than the deepest parts of the ocean.Tim Flannery, Where Wonders Await Us. New York Review of Books, December 2007 This is a common misconception based on a 1953 statement by George E.R. Deacon published in the Journal of Navigation, and largely refers to the scarce amount of seafloor bathymetry available at the time.{{Cite journal |last1=Jamieson |first1=Alan J |last2=Singleman |first2=Glenn |last3=Linley |first3=Thomas D |last4=Casey |first4=Susan |date=2020-12-21 |title=Fear and loathing of the deep ocean: why don't people care about the deep sea? |journal=ICES Journal of Marine Science |volume=78 |issue=3 |pages=797–809 |doi=10.1093/icesjms/fsaa234 |issn=1054-3139|doi-access=free }} The similar idea that more people have stood on the moon than have been to the deepest part of the ocean is likewise problematic and dangerous.File: Autonomous landers, Observing the deepest places on Earth.WebM) in deep-sea research; the fish seen is the abyssal grenadier (Coryphaenoides armatus).]]
Still, the deep-sea remains one of the least explored regions on planet Earth.{{cite journal |last1=Briand |first1=F. |last2=Snelgrove |first2=P. |date=2003 |title=Mare Incognitum? An overview |journal=CIESM Workshop Monographs |volume=23 |pages=5–27}}[https://www.researchgate.net/publication/365871261] Pressures even in the mesopelagic become too great for traditional exploration methods, demanding alternative approaches for deep-sea research. Baited camera stations, small crewed submersibles, and ROVs (remotely operated vehicles) are three methods utilized to explore the ocean's depths. Because of the difficulty and cost of exploring this zone, current knowledge is limited. Pressure increases at approximately one atmosphere for every 10 meters meaning that some areas of the deep sea can reach pressures of above 1,000 atmospheres. This not only makes great depths very difficult to reach without mechanical aids, but also provides a significant difficulty when attempting to study any organisms that may live in these areas as their cell chemistry will be adapted to such vast pressures.
See also
- {{annotated link|Deep ocean water}}
- {{annotated link|Submarine landslide}}
- {{annotated link|The Blue Planet|The Blue Planet}}
- {{annotated link|Blue Planet II|Blue Planet II}}
- {{annotated link|Nepheloid layer}}
- Biogenous ooze
- {{portal-inline|Oceans}}
References
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External links
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- [https://www.foraminifera.eu/weddell.html Deep Sea Foraminifera] – Deep Sea Foraminifera from 4400 meters depth, Antarctica – an image gallery and description of hundreds of specimens
- [https://ocean.si.edu/deep-sea Deep Ocean Exploration] on the Smithsonian Ocean Portal
- [https://deepseacreatures.org Deep-Sea Creatures] Facts and images from the deepest parts of the ocean
- [https://www.thedailyresearch.com/how-deep-is-the-ocean/ How Deep Is The Ocean] {{Webarchive|url=https://web.archive.org/web/20160615162236/https://www.thedailyresearch.com/how-deep-is-the-ocean |date=2016-06-15 }} Facts and infographic on ocean depth
{{physical oceanography|expanded=other}}
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