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The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word pelagic is derived from Ancient Greek πέλαγος (pélagos) 'open sea'. [1] The pelagic zone can be thought of as an imaginary cylinder or water column between the surface of the sea and the bottom.
Alternatively, marine habitats can be divided into pelagic and demersal zones. Pelagic habitats are found near the surface or in the open water column, away from the bottom of the ocean. Demersal habitats are near or on the bottom of the ocean. An organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish.
The oceanic zone is typically defined as the area of the ocean lying beyond the continental shelf (e.g. the neritic zone), but operationally is often referred to as beginning where the water depths drop to below 200 metres (660 ft), seaward from the coast into the open ocean with its pelagic zone.
The epipelagic zone, otherwise known as the sunlit zone or the euphotic zone, goes to a depth of about 200 meters (656 feet). It is the depth of water to which sunlight is able to penetrate. Although it is only 2 to 3 percent of the entire ocean, the epipelagic zone is home to a massive number of organisms. [3]
In contrast, species floating on the ocean's surface during one life cycle stage often (though not always) have pelagic larval stages. Velella and Porpita release jellyfish (medusae), [ 120 ] and while little is known about Porpita medusae , Velella medusae could possibly sink into deeper water, [ 120 ] or remain near the surface, where they ...
Pelagic zones. The mesopelagic zone includes the region of sharp changes in temperature, salinity and density called the thermocline, halocline, and pycnocline respectively. [1] The temperature variations are large; from over 20 °C (68 °F) at the upper layers to around 4 °C (39 °F) at the boundary with the bathyal zone. [5]
Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many
Marine geology or geological oceanography is the study of the history and structure of the ocean floor. It involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal zone. Marine geology has strong ties to geophysics and to physical oceanography.