Deep sea
The deep sea is broadly defined as the
Organisms living within the deep sea have a variety of adaptations to survive in these conditions.[5] 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.[6] Marine snow is organic material that has fallen from upper waters into the deep sea.[7]
In 1960, the bathyscaphe Trieste descended to the bottom of the Mariana Trench near Guam, at 10,911 m (35,797 ft; 6.780 mi), the deepest known spot in any ocean. If Mount Everest (8,848 m or 29,029 ft or 5.498 mi) were submerged there, its peak would be more than 2 km (1.2 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.[8] In May and June 2009, the hybrid-ROV Nereus returned to the Challenger Deep for a series of three dives to depths exceeding 10,900 m (35,800 ft; 6.8 mi).
Environmental characteristics
Light
Natural light does not penetrate the deep ocean, with the exception of the upper parts of the
Pressure
Because
Salinity
Salinity is remarkably constant throughout the deep sea, at about 35 parts per thousand.[9] 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].
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
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.[10]
In hydrothermal vents the temperature of the water as it emerges from the "black smoker" chimneys may be as high as 400 °C (it is kept from boiling by the high hydrostatic pressure) while within a few meters it may be back down to 2 to 4 °C.[11]
Biology
Regions below the
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]
The midwater fish have special adaptations to cope with these conditions—they are small, usually being under 25 centimetres (10 in); 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]
Because light is so scarce, fish often have larger than normal, tubular eyes with only
Organisms in the deep sea are almost entirely reliant upon sinking living and dead organic matter which falls at approximately 100 meters per day.
Despite being so isolated deep sea organisms have still been harmed by human interaction with the oceans. The London Convention[30] aims to protect the marine environment from dumping of wastes such as sewage sludge[31] 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.[32] 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.[33] Deep sea trawling is also harming the biodiversity by destroying deep sea habitats which can take years to form.[34] 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.[35]
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
Adaptation to hydrostatic pressure
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.[40][41]
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 5000m, C.armatus and C.yaquinae have specific substitutions on the active sites of α-Actin, which serves as the main component of muscle fiber.[42] These specific substitutions, Q137K and V54A from C.armatus or I67P from C.yaquinae are predicted to have importance in pressure tolerance.[42] 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.[43] It was found that deep sea fish have more salt bridges in their actins compared to fish inhabiting the upper zones of the sea.[42]
In relations to protein substitution, specific osmolytes were found to be abundant in deep sea fish under high hydrostatic pressure. For certain chondrichtyans, it was found that Trimethylamine N-oxide (TMAO) increased with depth, replacing other osmolytes and urea.[44] 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.
Exploration
It has been suggested that more is known about the Moon than the deepest parts of the ocean.[45] 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.[46] 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.[46]
Still the deep-sea remains one of the least explored regions on planet Earth.
See also
- Deep ocean water – Cold, salty water deep below the surface of Earth's oceans
- Submarine landslide – Landslides that transport sediment across the continental shelf and into the deep ocean
- The Blue Planet – 2001 British nature documentary television series
- Blue Planet II – 2017 British nature documentary television series
- Nepheloid layer – layer of water in the deep ocean basin, above the ocean floor, that contains significant amounts of suspended sediment
- Biogenous ooze
- Oceans portal
References
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- ^ US Department of Commerce, National Oceanic and Atmospheric Administration. "What is marine snow?". oceanservice.noaa.gov. Retrieved 2022-09-29.
- ^ Horstman, Mark (2003-07-09). "Hope floats for lost deep-sea explorer". www.abc.net.au. Archived from the original on 2010-09-27. Retrieved 2021-05-07.
- ^ a b Claus Detlefsen. "About the Marianas" (in Danish) Ingeniøren / Geological Survey of Denmark and Greenland, 2 November 2013. Accessed: 2 November 2013.
- ^ MarineBio (2018-06-17). "The Deep Sea". MarineBio Conservation Society. Retrieved 2020-08-07.
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- ^ Snelgrove, Paul; Grassle, Fred (1995-01-01). "What of the deep sea's future diversity?". Oceanus. 38 (2). Archived from the original on 2020-07-29. Retrieved 24 March 2020.
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- ^ 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
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External links
- Deep Sea Foraminifera – Deep Sea Foraminifera from 4400 meters depth, Antarctica - an image gallery and description of hundreds of specimens
- Deep Ocean Exploration on the Smithsonian Ocean Portal
- Deep-Sea Creatures Facts and images from the deepest parts of the ocean
- How Deep Is The Ocean Archived 2016-06-15 at the Wayback Machine Facts and infographic on ocean depth