Deep sea

As deep you usually referred to the completely lightless ( aphotic ) areas of the sea that are below a depth of 800 m. More than 70% of the sea is deep sea world.

In the deep sea, there is no primary production except by the hydrothermal vents, also called black smokers because in the deep sea there is due to the absence of light, no plants. Despite the seemingly very hostile conditions developed here a variety of wildlife. The food chain consists of predators and scavengers or for their nutrition on symbiotic bacteria and archaea commanded animals.

Data

The temperature is consistently low (-1 ° C to 4 ° C). At a depth of 10,000 meters, a pressure of about 1,000 bar prevails. Strong currents are rare, and seasonal fluctuations are limited to the amount of detritus that falls here from the through -exposed areas and is the most important food source for the deep sea.

The lying in water depths of 1,000 m or more areas of the deep sea covering an area of ​​about 318 million km ², which represents about 62 % of the earth's surface.

In the deep sea or on the edges are remarkable tectonic zones:

• Mid-ocean ridge - mountain system of the ocean, first discovered in the Atlantic
• Ocean basins - available in all parts of the ocean extensive and deep basin
• Deep-sea trenches - especially in the Pacific Ocean located so-called trenches. The ( after a measurement of 1957) 11,034 m deep Witjastief 1 ( Mariana Trench, Pacific Ocean ) is considered deepest known point in the world 's oceans.

The back and gutters were examined only in recent decades by geophysical methods and found to be "seams of plate tectonics ." They make their presence felt among other things in the earth's gravitational field and in the distribution of earthquakes.

The counterpart of the deep sea is the " shallow lake ", especially the continents of offshore shelf areas.

Structure

The ocean is divided into two major areas:

Midwater

The pelagic zone (Greek pelagos, Sea ') is the habitat of the free water. The pelagic zone is in lakes and the sea shore of the distant open water area above the soil zone ( benthic ).

In the sea, the pelagic zone, the morphological classification of the lake bed is divided according to, in five zones:

• The epipelagial are the top 200 meters of the water column of the open water ( pelagic zone ) in the sea. This cleared by ( (eu) photic ) depth zone is characterized by a positive bioproductivity ( trophogenic zone, ie positive mass and energy balance, the strongest structure of biomass ) and the highest species richness within the ecosystem characterized. In epipelagial there is sufficient light for higher plants and photoautotrophic microorganisms to perform photosynthesis. In addition to plankton here lives the active floating Nekton, ie fish, crustaceans and cephalopods. Down the epipelagial is limited by the mesopelagic.
• The area between 200 meters to about 1,000 meters above sea depth is referred to as mesopelagial; From here begins the actual deep sea. At this depth is still little blue light present. The pressure is 1000 meters deep about 100 bar. That is about 1,000 tons per square meter or 100 kg per square centimeter. Vegetation is no longer available. From time to time you will find plankton. In mesopelagial live for example, the deep-sea Beilfische.
• The Bathypelagial ranges of 1,000 to 4,000 meters depth. The pressure is 4,000 meters deep about 400 bar. There is no sunlight available, only fish and bacteria produce artificial light in the form of bioluminescence. Among the living at this depth deep sea fishing, there are also deep-sea angler fish.
• The Abyssopelagial ( 4,000-6,000 m) is the depth zone 4000-6000 m depth. Here, the temperature is close to the freezing point, the pressure is 400 times higher than on the surface. In Abyssopelagial lives such as the deep sea cancer.
• The Hadopelagial ( 6000-11000 m ) is the lowest zone in the sea, ranging from 6,000 up to 11,000 meters deep, the deepest point in the ocean. Here, the pressure is up to 1100 times higher than at the surface. The temperature is close to freezing as in Abyssopelagial. Nonetheless there are living things, such as the bristle worm.

According to some marine biologists can Abyssopelagial, Bathypelagial and pelagic Hadal (also Hadopelagial, Hadalpelagial, hadopelagische zone) do not distinguish due to their similar hydrological and biological properties, so they are combined into one zone of the deep sea.

The pelagic zone can be similar to the benthic ( littoral and profundal analog ) divided into two biological production zones.

The boundary between the two zones is called the compensation level ( biomass built up by photosynthesis is broken down by respiration again, the biogenic net production is approximately equal to zero ). The time available for photosynthesis residual amount of light is so low that there is little biomass can be built up by the plants (producers). This is, as the generated oxygen through respiration of them again completely consumed. In the larger (ie tropholytic ) water depths must therefore all the necessary oxygen and nutrients are all for the organisms to life by mass transfer from the trophogenic layer or the inhabitants rise to (vertical migration) and get active substances required. The actual position of trophogenic layer and thus the compensation level depends on the actual photosynthesis, which is in turn influenced by various factors. Thus, the light transmittance of the water on the local conditions (water turbidity, plankton density ) is determined, the photosynthesis rate fluctuates at higher latitudes directly with the course of the seasons.

Benthic

The benthic zone ( Greek) is the area of the seabed, the latter is also divided into horizontal zones:

• The bathyal ( gr Bathys, depth ') is the area of the continental slope, where the water descends from the flat portion of the continental shelf to the abyssal plain, ranging from 200 m to 2.000/3.000 m depth.
• The abyssal region (Latin abyssus, Abyss' ) is the area of the ocean basins with 2.000/3.000 m to 6,000 m depth
• The Hadalzone (Greek hades, underworld '), which includes the ocean depths ranging from 6,000 m to 10,000 m in depth.

On the seabed there are some ecosystems, inorganic materials for their energy ( chemosynthesis ) use. The starting point are chemoautotrophic bacteria that live in symbiosis with beard worms and clams, of which in turn can feed other animals. These ecosystems occur where water emerges from the ground, which is enriched, for example, with methane and hydrogen sulfide. These places are found both in the area of ​​mid-ocean ridges and the subduction zones and continental shelves.

In the area of the back, there are hot springs, where up to 400 ° C outlet hot water, and hot springs, where the hot water begins to cool already deep in the ground and after emerging from the soil only slightly warmer than the surrounding cold seawater is. The hot springs can also by an exothermic chemical process occur, the serpentinization is converted to serpentinite in the peridotite by absorbing large amounts of sea water, with the addition of methane, hydrogen sulfide and hydrogen gas ( H2) can be generated. This mechanism is not restricted to the mid-ocean ridges, so that you can watch such hot springs, for example, in the spreading zone of a backarc basin. For the first time such a source was discovered in 2000 (Lost City). The heated water generates so-called black and white smokers, on average 20 m to 25 m high chimneys, which consist of precipitated minerals.

At subduction zones and continental shelves to find cold springs (see methane source or Cold Seep ), where the light emerging from the ground water is not heated. While this is place on a cold source ecosystem is also based on the symbiosis with chemoautotrophic bacteria, but since they appear in a few hundred meters depth in both several thousand meters depth as well as on the edge of the deep sea on the continental slopes, found on such species spectrum can be more extensive. The area of ​​the cold springs is characterized by the fact that calcium carbonate precipitates in crusts and that methane hydrates can be found.

History of Research

The history of deep-sea research is relatively young, since the ruling in the deep sea extreme conditions, make huge technical demands on the people.

Importance of deep-sea

Oceans can be roughly divided into the near-surface layers and the deep sea. While the former respond within weeks and months because of the direct coupling to the rapidly varying atmospheric conditions with variations of the flows, the temperatures and the salinity changes in the deep sea are caused by variations in the surface conditions in limited areas of the polar and subpolar latitudes and play out involved because of the enormous masses of water in periods of many decades to centuries from. Especially for issues relating to global climate change, the deep sea in view of anthropogenic climate influence plays an important role specifically.

The importance of polar and sub-polar regions is based on the conditional density anomaly of water ( maximum density at about 4 ° C) and its modification by the salinity of the oceans. The salinity of the sea averages about 34.7 ‰, whereby the properties of the water are changed considerably. The temperature of the density maximum shifts with an average salinity of 34.7 ‰ to -3.8 ° C and thereby gets below the freezing point of -1.9 ° C. This results in the sea when cooled to the onset of ice formation to a convection: cooled (and therefore denser ) of water drops, warmer (and less dense ) rises from the lower layers. Here, the warmer water gives its heat content to the atmosphere and decreases with cooling back down again into the depths. The water takes on atmospheric gases (eg carbon dioxide ) and thus provides a transport of these. In the deep sea For this reason, the Konvektionsgebiete are also those marine areas, where the highest proportions of anthropogenic carbon dioxide can be found.

In addition to these vertical convective self- horizontal ocean currents play a significant role in the deep sea (see also: global conveyor belt). Depending on the current surface conditions caused cold water masses of different characteristics that can be traced along their propagation routes in the deep sea. These cold water masses are distinguished by their temperature, salinity and density values ​​, the oxygen content or the content of anthropogenic trace gases from their formation region. The deepest water masses are predominantly Antarctic origin, they are also referred to as " Antarctic Bottom Water ", or in English as " Antarctic Bottom Water" ( AABW ). A slightly lower density have the water masses Arctic origin. These are called " North Atlantic Deep Water ", and in referred to as " North Atlantic Deep Water" ( NADW ), English, which is as powerful intermediate layer above the ground water.

Issues in Research

Although the deep sea occupies the major part of our planet, is less well known than the surface of the moon about it. This is due to their relative inaccessibility: Few countries have Lander, deep sea suitable for submarines or ships large enough to pull out samples from the deep sea. So requires sampling at a depth of 8,000 m already 11 km long cable. In addition, it takes 24 hours for a device deigning to this depth and bring up again. The equipment and ships are very expensive, a large research ship costs tens of thousands of euros per day. Animals whose behavior is to be examined, and shall also be observed in their habitat or brought up in special pressure vessels, since they would survive the enormous pressure changes are not alive. Due to the food shortage deep sea animals are also usually not very numerous, so that many samples are necessary to prove a kind at all.

Political aspects

2006, the Federal Republic of Germany has backed up for 15 years exploration rights to two manganese deposits in the Pacific on an area as large as Lower Saxony and Schleswig -Holstein together. Boundary lines do not exist or are even near the coast are often disputed.

The deep sea in art and literature

The fascination of the unknown is also reflected in literature, movies and music:

• The film Abyss - Abyss of Death 1989 plays in the deep sea. He received for his visual effects also in 1990 and an Academy Award and was nominated for three more.

• Frank Schätzing treated in his novel The Swarm the unexplored depths of the seas. He describes so-called Yrr - fictional deep-sea creatures of unknown intelligence, superior to human far.

• The German - Swiss heavy metal band The Ocean published in 2013, the concept album pelagic zone, in which they set to music a journey from the sea surface to the bottom of the deep sea. The individual songs are categorized according to the five zones of the pelagic zone.