pelagic zone

(redirected from Pelagic Realm)

pelagic zone:

see oceanocean,
interconnected mass of saltwater covering 70.78% of the surface of the earth, often called the world ocean. It is subdivided into four (or five) major units that are separated from each other in most cases by the continental masses. See also oceanography.
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Pelagic Zone


that part of a lake, sea, or ocean that is the habitat of pelagic organisms—plankton, necton, and pleuston. The pelagic zone is opposed to the benthic zone, that is, the bottom of the body of water, which is inhabited by benthos.

In oceans and seas, the pelagic zone is divided horizontally into two regions: the neritic (water above the shelf) and the oceanic (all the remaining water). Vertically the zone is divided, usually depending on the degree of illumination, into three regions: the euphotic (well illuminated), the dysphotic (feebly illuminated), and the aphotic (lightless). The zone is also broken down according to the distribution of life into the epipelagic, mesopelagic, and deep-water regions. In freshwaters, the pelagic zone is divided horizontally into two regions: the shore region (the water near the shore) and the pelagic region proper (all the remaining water). Vertically three regions are distinguished according to the rate of temperature drop: the epilimnion, the metalimnion, and the hypolimnion.

References in periodicals archive ?
In the pelagic realm, exploitation of tuna, billfishes and increasingly sharks for their fin, (6) by long-lines and similar gear has strongly modified oceanic ecosystems, which now have much reduced biomasses of large predators.
According to Omori (1974), out of a total of about 2,000 species of shrimps recorded from the world oceans, as many as 210 species pass their complete life in the pelagic realm.
The primary explanation for the prevalence of transparency in this environment is that it is the only form of camouflage in the pelagic realm that is successful from all viewpoints and at all depths.
Whereas the pelagic realm is home to phytoplankton, zooplankton, neuston, nekton, and flying organisms that feed near the surface, the chapter mentions only phytoplankton, crustaceans, and three small mesopelagic fishes, thereby omitting gelatinous zooplankton, squids, sharks, mackerels, tunas, bill fishes, sea turtles, seabirds, pinnipeds, and cetaceans.
A small apposition eye is sufficient in the relatively well-lit upper regions of the pelagic realm, where juvenile and adolescent pelagic decapods and euphausiids are to be found (Baker, 1970; Foxton, 1970; Marshall, 1979), but as shrimps increase in size and daily movement to the ecological refuge provided by depth (King and Butler, 1985) becomes a viable strategy, their eyes develop to suit a more oligophotic environment.