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The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. [1] The demersal zone is just above the benthic zone and forms a layer of the larger profundal zone .
Benthic-pelagic coupling are processes that connect the benthic zone and the pelagic zone through the exchange of energy, mass, or nutrients. These processes play a prominent role in both freshwater and marine ecosystems and are influenced by a number of chemical, biological, and physical forces that are crucial to functions from nutrient cycling to energy transfer in food webs.
Altogether, the pelagic zone occupies 1,330 million km 3 (320 million mi 3) with a mean depth of 3.68 km (2.29 mi) and maximum depth of 11 km (6.8 mi). [2] [3] [4] Pelagic life decreases as depth increases. 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 ...
Marine habitats can be broadly divided into pelagic and demersal habitats. Pelagic habitats are the habitats of the open water column, away from the bottom of the ocean. Demersal habitats are the habitats that 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 pelagic food web, showing the central involvement of marine microorganisms in how the ocean imports nutrients from and then exports them back to the atmosphere and ocean floor. A marine food web is a food web of marine life. At the base of the ocean food web are single-celled algae and other plant-like organisms known as phytoplankton.
As with oceans, the benthic zone is the floor of the lake, composed of accumulated sunken organic matter. The littoral zone is the zone bordering the shore; light penetrates easily and aquatic plants thrive. The pelagic zone represents the broad mass of water, down as far as the depth to which no light penetrates. [9]
Demersal fish live on or near the sea floor, while pelagic fish live in the water column away the sea floor. Examples of such shallow water demersal fish, found in both tropical and temperate waters around the world, are seahorses, triplefins, wrasse and flounder. As demersal fish, all these fish spend most of their time on or near the sea floor.
Demersal fish can be divided into two main types: strictly benthic fish which can rest on the sea floor, and benthopelagic fish which can float in the water column just above the sea floor. Benthopelagic fish have neutral buoyancy , so they can float at depth without much effort, while strictly benthic fish are denser, with negative buoyancy so ...