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The pelagic zone contrasts with the benthic and demersal zones at the bottom of the sea. The benthic zone is the ecological region at the very bottom, including the sediment surface and some subsurface layers. Marine organisms such as clams and crabs living in this zone are called benthos. Just above the benthic zone is the demersal zone.
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.
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]
Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf. 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.
A school of large pelagic predator fish (bluefin trevally) sizing up a school of small pelagic prey fish (). Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs.
Layers of the pelagic zone. The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of 1,000 to 4,000 m (3,300 to 13,000 ft) below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below.
The Atlantic Ocean is teeming with life, but for the first time researchers have discovered dead zones in these waters - areas low in both oxygen and salinity - off the coast of Africa. Fish can't ...
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 ...