Pelagic zone

The pelagic zone (Greek πέλαγος Pelagos Sea ') is in lakes and the sea shore of the distant open water area above the soil zone ( benthic ). In lakes it ranges from the middle of the lake towards the shore up to the first rooted aquatic plants. In the sea -coast is with midwater the high seas, that is called the open sea. Sedimentary rocks, from which a similar development environment is assumed to be referred to as pelagic sedimentary rocks.

The Pelagie zones

In the sea, the pelagic zone is divided, according to the geomorphological division of the bed along the continental slope, in five depth zones.

Epipelagial

The epipelagial ( gr επί epi "on " ) extends to a depth of 200 meters in the sea or, more rarely, in a lake and is characterized by a positive bioproductivity and the highest species richness within the ecosystem. In addition to plankton here lives the Nekton - especially fish, marine mammals, crustaceans and cephalopods. The epipelagische zone is flooded by the sun and therefore allows multicellular algae, higher plants and photoautotrophic microorganisms to perform photosynthesis. The portion of the Epipelagials in which this is possible will depend on the characteristics of a body of water and means euphotic zone.

Mesopelagial

The mesopelagic (Greek μέσον Méson " centered" ) extends from 200 to 1000 meters depth and thus lies between the bright and the dark depth zones, how it got its name derives. Its lower limit marks the beginning of the actual deep sea, the aphotic zone. Although still a little blue light penetrates into these depths, there is no photosynthesis and therefore no more vegetation; from time to time be found but plankton. In mesopelagial live example, the deep-sea Beilfische.

Bathypelagial

The Bathypelagial ( gr βαθύς Bathys " deep " ) ranges from 1000 to 4000 meters depth. The pressure bar in this depth zone to about 400. It is no longer available sunlight, only a few fish and bacteria produce light by bioluminescence. Among the surviving animals in this zone can be found at other squid, octopus, starfish and large whales.

Abyssopelagial

The Abyssopelagial ( gr ἄβυσσος Abyss " bottomless " ) ranges of 4000 to 6000 meters depth. The animals living here, including deep-sea angler fish and giant squid must withstand near freezing temperatures and pressures up to 600 bar. Since food is scarce at these depths, have in some animals developed strikingly large mouths so that they can make any prey.

Hadopelagial

The Hadopelagial ( gr Ἁΐδης, Hades, the underworld ) is the deepest zone, ranging from 6000 up to 11000 meters deep, the deepest point in the ocean. Here, the pressure is up to 1100 times higher than at the surface. Sunlight is not available at the Hadopelagial and the temperature as close to freezing in Abyssopelagial. Among the creatures occurring here include the bristle worms.

According to some marine biologists Bathypelagial let Abyssopelagial and Hadopelagial (also pelagic Hadal, Hadalpelagial, hadopelagische zone) do not differ based on their hydrological and biological characteristics. For this reason, they are often combined to form a zone of the deep sea.

Biological production zones

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 (photosynthesis = respiration ⇒ Biogenic net production = 0). It is located where the time available for photosynthesis residual amount of light is so low that generated by the plants (producers) in the light and dark reaction, oxygen and biomass by respiration of them are again completely consumed. In the larger (ie tropholytic ) water depths must be therefore 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.

The living in the pelagic organisms belong to the passive drifting plankton or the active floating Nekton.