Wednesday, September 19, 2012

The deep sea, or deep layer

The deep sea, or deep layer,[1] is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms (1800 m) or more. Little or no light penetrates this part of the ocean and most of the organisms that live there rely for subsistence on falling organic matter produced in the photic zone. Sony VAIO PCG-3B1M Battery
For this reason scientists once assumed that life would be sparse in the deep ocean but virtually every probe has revealed that, on the contrary, life is abundant in the deep ocean.
From the time of Pliny until the expedition in the ship Challenger between 1872 and 1876 to prove Pliny wrong; Sony VAIO PCG-3C1T Battery
its deep-sea dredges and trawls brought up living things from all depths that could be reached. Yet even in the twentieth century scientists continued to imagine that life at great depth was insubstantial, or somehow inconsequential. The eternal dark, the almost inconceivable pressure, Sony VAIO PCG-3D1M Battery
and the extreme cold that exist below one thousand meters were, they thought, so forbidding as to have all but extinguished life. The reverse is in fact true....(Below 200 meters) lies the largest habitat on earth.
In 1960 the Bathyscaphe Trieste descended to the bottom of the Mariana Trench near Guam, at 35,798 feet or 6.77 miles (10,911 meters), the deepest spot in any ocean. Sony VAIO PCG-3G2M Battery
If Mount Everest were submerged there, its peak would be more than a mile beneath the surface. At this great depth a small flounder-like fish was seen moving away from the bathyscaphe's spotlight. The Trieste was retired and for a while the Japanese remote-operated vehicle (ROV) Kaikō was the only vessel capable of reaching this depth. Sony VAIO PCG-5R1M Battery
It was lost at sea in 2003. In May and June 2009, the hybrid-ROV (HROV) Nereus returned to the Challenger Deep for a series of three dives to depths exceeding 10900 meters.
It has been suggested that more is known about the Moon than the deepest parts of the ocean. Sony VAIO PCG-7141M Battery
Until the late 1970s little was known about the extent of life on the deep ocean floor but the discovery of thriving colonies of shrimps and other organisms around hydrothermal vents changed that. Before the discovery of the undersea vents, it had been accepted that almost all life on earth obtained its energy (one way or another) from the sun. Sony VAIO PCG-7143M Battery
The new discoveries revealed groups of creatures that obtained nutrients and energy directly from thermal sources and chemical reactions associated with changes to mineral deposits. These organisms thrive in completely lightless and anaerobic environments, in highly saline water that may reach 300 °F (150 °C), Sony VAIO PCG-7151M Battery
drawing their sustenance from hydrogen sulfide, which is highly toxic to almost all terrestrial life. The revolutionary discovery that life can exist under these extreme conditions changed opinions about the chances of there being life elsewhere in the universe. Scientists now speculate that Europa, Sony VAIO PCG-7154M Battery
one of Jupiter's moons, may be able to support life beneath its icy surface, where there is evidence[3] of a global ocean of liquid water.
Natural light does not penetrate the deep ocean, with the exception of the upper parts of the mesopelagic. Sony VAIO PCG-7162M Battery
Photosynthesis is not possible, precluding any photosynthetically based primary productivity. Bioluminescence is the only light available at these depths. This lack of light means the organisms have to rely on senses other than vision. It may also have a selective effect on the locomotory habits of the animals and on their propulsive systems. Sony VAIO PCG-7181M Battery
Pressure is the greatest environmental factor acting on deep-sea organisms. Pressure increases 1 atmosphere (atm) for each 10 m in depth. In the deep sea, although most of the deep sea is under pressures between 200 and 600 atm, the range of pressure is from 20 to 1,000 atm. Sony VAIO PCG-41112M Battery
Pressure exhibits a great role in the distribution of deep sea organisms. Until recently, people lacked detailed information on the direct effects of pressure on most deep-sea organisms, because virtually all organisms trawled from the deep sea arrived at the surface dead or dying. Sony VAIO PCG-7153M Battery
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. Some of these have been maintained for experimental purposes, and researchers are obtaining more knowledge of the biological effects of pressure. Sony VAIO PCG-71312M Battery
Salinity is remarkably constant throughout the deep sea. There are some minor differences in salinity, but none that are ecologically significant, except in the Mediterranean & Red seas.
The two areas of greatest and most rapid temperature change in the oceans are the transition zone between the surface waters and the deep waters, Sony VAIO PCG-7144M Battery
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. Sony VAIO PCG-7191L Battery
Thermoclines are strongest in the tropics, where the temperature of the epipelagic zone is usually above 20°C. From the base of the epipelagic, the temperature drops over several hundred meters to 5 or 6°C at 1,000 meters. It continues to decrease to the bottom, but the rate is much slower. Below 3,000 to 4,000 m, the water is isothermal. Sony VAIO PCG-3C1M Battery
At any given depth, the temperature is practically unvarying over long periods of time. There are no seasonal temperature changes, nor are there any annual changes. No other habitat on earth has such a constant temperature. Sony VAIO PCG-3F1M Battery
Hydrothermal vents are the direct contrast with constant temperature. In these systems, 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 - 4°C. Sony VAIO PCG-3H1M Battery
Regions below the epipelagic are divided into further zones, beginning with the mesopelagic which spans from 200 to 1000 meters below sea level, where a little light penetrates while still being insufficient for primary production. Below this zone the deep sea proper begins, consisting of the aphotic bathypelagic,abyssopelagic and hadopelagicSony VAIO PCG-3J1M Battery
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.
Instead of relying on gas for their buoyancy, many species have jelly-like flesh consisting mostly of glycosaminoglycans, which has very low density. Sony VAIO PCG-8141M Battery
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 productammonium chloride, which is lighter than the surrounding water.
The midwater fish have special adaptations to cope with these conditions—they are small, usually being under 25 centimetres (10 in); Sony VAIO PCG-8161M Battery
they have slow metabolismsand unspecialized diets, preferring to sit and wait for food rather than waste energy searching for it. They have elongated bodies with weak, watery muscles andskeletal structures. They often have extendable, hinged jaws with recurved teeth. Sony VAIO PCG-3C2M Battery
Because of the sparse distribution and lack of light, finding a partner with which to breed is difficult, and many organisms are hermaphroditic.
Because light is so scarce, fish often have larger than normal, tubular eyes with only rod cells. Their upward field of vision allows them to seek out the silhouette of possible prey. Sony VAIO PCG-5N2M Battery
Prey fish however also have adaptations to cope withpredation. These adaptations are mainly concerned with reduction of silhouette, 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, and counter illumination via bioluminescence. Sony VAIO PCG-5P1M Battery
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. Sony VAIO PCG-5S1M Battery
Flashlight fish have this plus photophores, which combination they use to detect eyeshine in other fish (see Tapetum lucidum).
Organisms in the deep sea are almost entirely reliant upon sinking living and dead organic matter which falls at approximately 100 meters per day. Sony VAIO PCG-9Z1M Battery
In addition, only about 1-3% of the production from the surface reaches the sea bed mostly in the form of marine snow. Larger food falls, such as whale carcasses, also occur and studies have shown that these may happen more often than currently believed.Sony VAIO PCG-7171M Battery
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.[7] In addition, there are a number of filter feeders that feed upon organic particles using tentacles, such as Freyella elegans.[8] Sony VAIO PCG-7186M Battery
Marine bacteriophages play an important role in cycling nutrients in deep sea sediments. They are extremely abundant (between 5x1012 and 1x1013 phages per square meter) in sediments around the world.[9]
There are a number of species that do not primarily rely upon dissolved organic matter for their food and these are found at hydrothermal vents. Sony VAIO PCG-81112M Battery
One example is the symbiotic relationship between the tube worm Riftia and chemosynthetic bacteria. It is this chemosynthesis that supports the complex communities that can be found around hydrothermal vents.[10] These complex communities are one of the only ecosystems on the planet that do not rely upon sunlight for the supply of energy. Sony VAIO PCG-31311M Battery
The deep sea is an environment completely unfriendly to humankind, and it should come as no surprise that it represents one of the least explored areas on Earth. Pressures even in the mesopelagic become too great for traditional exploration methods, demanding alternative approaches for deep sea research. Sony VAIO PCG-8152M Battery
Baited camera stations, small manned 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. Sony VAIO PCG-31111M Battery
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.Sony VAIO PCG-61111M Battery
Deep Ocean Water (DOW) is the name for cold, salty water found deep below the surface of Earth's oceans. Ocean water differs in temperature and salinity, with warm, relatively non-salty water found at the surface, and very cold salty water found deeper below the surface layer. Sony VAIO PCG-51112M Battery
Deep ocean water makes up about 90% of the volume of the oceans. Deep ocean water has a very low temperature, typically from 0 °C (32 °F) to 3 °C (37 °F), and a salinity of about 3.5% (35 psu).[1]
In specialized locations such as the Natural Energy Laboratory of Hawaii Sony VAIO PCG-51211M Battery
NELHA ocean water is pumped to the surface from approximately 3000 feet deep for applications in research, commercial and pre-commercial activities. DOW is typically used to describe ocean water at sub-thermal depths sufficient to provide a measurable difference in water temperature. Sony VAIO PCG-51212M Battery
When deep ocean water is brought to the surface, it can be used for a variety of things. Its most useful property is its temperature. At the surface of the Earth, most water and air is well above 3 °C. The difference in temperature is indicative of a difference in energy. Where there is an energy gradient, Sony VAIO PCG-41111M Battery
skillful application of science and engineering can harness that energy for productive use by humans. Assuming the source of deep ocean water is environmentally friendly and replenished by natural mechanisms, it forms a more innovative basis for cleaner energy than current fossil-fuel-derived energy. Sony VAIO PCG-41111V Battery
The simplest use of cold water is simply for air conditioning: using the cold water itself to cool air saves the energy that would be used by the compressors for traditional refrigeration. Another use could be to replace expensive desalination plants. When cold water passes through a pipe surrounded by humid air, condensation results. Sony VAIO PCG-61412V Battery
The condensate is pure water, suitable for humans to drink or for crop irrigation. Finally, via a technology called Ocean thermal energy conversion, the temperature difference can be turned into electricity.
Deep-sea fish is a term for any fish that lives below the photic zone of the ocean. Sony VAIO PCG-71112M Battery
The lanternfish is, by far, the most common deep-sea fish. Other deep sea fish include the flashlight fish, cookiecutter shark, bristlemouths,anglerfish, and viperfish.
Only about 2% of known marine species inhabit the pelagic environment. Sony VAIO PCG-81111V Battery
This means that they live in the water column as opposed to the benthic organisms that live in or on the sea floor . Deep-sea organisms generally inhabit bathypelagic (1000m-4000m deep) and abyssopelagic (4000m-6000m deep) zones. However, characteristics of deep-sea organisms, such as bioluminescence can be seen in the mesopelagic (200m-1000m deep) zone as well.Sony VAIO PCG-81111V Battery
The mesopelagic zone is the disphotic zone, meaning light there is minimal but still measurable. The oxygen minimum layer exists somewhere between a depth of 700m and 1000m deep depending on the place in the ocean. This area is also where nutrients are most abundant. Sony VAIO PCG-81212M Battery
The bathypelagic and abyssopelagic zones are aphotic, meaning that no light penetrates this area of the ocean. These zones make up about 75% of the inhabitable ocean space [2].
The zone that deep-sea fish do not inhabit is the epipelagic zone (0m-200m), which is the area where light penetrates the water and photosynthesis occurs. Sony VAIO PCG-81212V Battery
This is also known as the euphotic, or simply photic, zone. Because the photic zone typically extends only a few hundred meters below the water, about 90% of the ocean volume is invisible to humans. The deep-sea is also an extremely hostile environment, with temperatures that "rarely exceed 3°C and fall as low as -1.8°C" Sony VAIO PCG-51111M Battery
(with the exception of hydrothermal vent ecosystems that can exceed 350°C), low oxygen levels, and pressures between 20 and 1,000 atmospheres (between 2 and 100 megapascals)[3]..
Hydrostatic pressure increases by 1 atmosphere for every 10m in depth . Deep-sea organisms have the same pressure within their bodies that is being exerted on them from the outside, Sony VAIO VPCS13X9E/B battery
so they aren’t crushed by the extreme pressure. Their high internal pressure, however, results in the reduced fluidity of their membranes because molecules are squeezed together. Fluidity in cell membranes increases efficiency of biological functions, most importantly the production of proteins, Sony VAIO VPCS12V9E/B battery
so organisms have adapted to this circumstance by increasing the proportion of unsaturated fatty acids in the lipids of the cell membranes [5]. In addition to differences in internal pressure, these organisms have developed a different balance between their metabolic reactions from those organisms that live in the epipelagic zone. Sony VAIO VPCS12V9E/B battery
David Wharton, author of Life at the Limits: Organisms in Extreme Environments, notes “Biochemical reactions are accompanied by changes in volume. If a reaction results in an increase in volume, it will be inhibited by pressure, whereas, if it is associated with a decrease in volume, it will be enhanced,” Sony VAIO VPCF13M8E/B battery
This means that their metabolic processes must ultimately decrease the volume of the organism to some degree.
Most fish that have evolved in this harsh environment are not capable of surviving in laboratory conditions, and attempts to keep them in captivity have led to their deaths. Sony VAIO VPCF13Z0E/B battery
Deep-sea organisms contain gas-filled spaces (vacuoles). Gas is compressed under high pressure and expands under low pressure. Because of this, these organisms have been known to blow up if they come to the surface [7]. Other complications arise from nitrogen narcosis and decompression sickness, which also occur in humans. Sony VAIO VPCM13M1E/L battery
Nitrogen narcosis occurs because the absorption of gases in the blood, especially nitrogen, increase at greater depths. The result is similar to drunkenness. Decompression sickness occurs when excess gases cannot be removed from the blood stream fast enough when an organism rises in the water column. Sony VAIO VPCM13M1E/W battery
The decreased pressure makes the gases expand and small bubbles of nitrogen form in the blood stream as well as tissues. The result of this can be bone damage, extreme pain, physical debilitation, and even death [8]. This can be seen in the case of the Frilled Shark that was found in shallow waters near Japan. Sony VAIO VPCF22M1E battery
They usually live at a depth of 1,500m, so when this specimen was transferred to a marine park it died within a few hours [9]. For this reason little is known about them, as there are limitations to the amount of fruitful research that can be carried out on a dead specimen and deep-sea exploratory equipment is very expensive. Sony VAIO VPCF11M1E/H battery
As such, many species are known only to scientists and have therefore retained their scientific name.
The fish of the deep-sea are among the strangest and most elusive creatures on Earth. In this deep unknown lie many unusual creatures that have yet to be studied. Sony VAIO VPCF13M0E/B battery
Since many of these fish live in regions where there is no natural illumination, they cannot rely solely on their eyesight for locating prey and mates and avoiding predators; deep-sea fish have evolvedappropriately to the extreme sub-photic region in which they live. Many of these organisms are blind and rely on their other senses, Sony VAIO VPCYB2M1E battery
such as sensitivities to changes in local pressure and smell, to catch their food and avoid being caught. Those that aren’t blind have large and sensitive eyes that can utilize bioluminescent light (discussed below). These eyes can be as much as 100 times more sensitive to light than human eyes. Sony VAIO VPCYB3V1E battery
Also, to avoid predation, many species are dark to blend in with their environment [10].
Many deep-sea fish are bioluminescent, with extremely large eyes adapted to the dark. Bioluminescent organisms are capable of producing light biologically through the agitation of molecules of luciferin, which then produce photons of light. Sony VAIO VPCY11M1E battery
This process must be done in the presence of oxygen. These organisms are common in the mesopelagic region and below (200m and below). More than 50% of deep-sea fish as well as some species of shrimp and squid are capable of bioluminescence. About 80% of these organisms have photophores – light producing glandular cells that contain luminous bacteria bordered by dark colorings. Sony VAIO VPCS12L9E/B battery
Some of these photophores contain lenses, much like those in the eyes of humans, which can intensify or lessen the emanation of light. The ability to produce light only requires 1% of the organism's energy and has many purposes: It is used to search for food and attract prey, like the anglerfish; claim territory through patrol; Sony VAIO VPCF11S1E/B battery
communicate and find a mate; and distract or temporarily blind predators to escape. Also, in the mesopelagic where some light still penetrates, some organisms camouflage themselves from predators below them by illuminating their bellies to match the color and intensity of light from above so that no shadow is cast. This tactic is known as counter illumination [11]Sony VAIO VPCYB3V1E/R Battery
The lifecycle of deep-sea fish can be exclusively deep water although some species are born in shallower water and sink upon maturation. Regardless of the depth where eggs and larvae reside, they are typically pelagic. This planktonic – drifting – lifestyle requires neutral buoyancy. Sony VAIO VPCF23P1E Battery
In order to maintain this, the eggs and larvae often contain oil droplets in their plasma[12]. When these organisms are in their fully matured state they need other adaptations to maintain their positions in the water column. In general, water’s density causes upthrust – the aspect of buoyancy that makes organisms float. Sony VAIO VPCF23N1E Battery

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