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The ocean's surface acts like a skin between the atmosphere above and the water below, and hosts an ecosystem unique to this environment. This sun-drenched habitat can be defined as roughly one metre in depth, as nearly half of UV-B is attenuated within this first meter. [2]
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word βένθος ( bénthos ), meaning "the depths". [ 1 ]
The ocean zones can be grouped by light penetration into (from top to bottom): the photic zone, the mesopelagic zone and the aphotic deep ocean zone: The photic zone is defined to be "the depth at which light intensity is only 1% of the surface value". [12]: 36 This is usually up to a depth of approximately 200 m in the open ocean.
Temperatures in the Mesopelagic zone range from 5 to 4 °C (41 to 39 °F). The pressure is higher here, it can be up to 10,100 kilopascals (1,460 psi) and increases with depth. [1] 54% of the ocean lies in the Bathypelagic (aphotic) zone into which no light penetrates. This is also called the midnight zone and the deep ocean.
From shallow waters to the deep sea, the open ocean to rivers and lakes, numerous terrestrial and marine species depend on the surface ecosystem and the organisms found there. [28] The ocean's surface acts like a skin between the atmosphere above and the water below, and harbours an ecosystem unique to this environment.
Marine biology is the scientific study of the biology of marine life, organisms that inhabit the sea.Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather than on taxonomy.
[notes 1] The hydrosphere plays an important role in the existence of the atmosphere in its present form. Oceans are important in this regard. When the Earth was formed it had only a very thin atmosphere rich in hydrogen and helium similar to the present atmosphere of Mercury. Later the gases hydrogen and helium were expelled from the atmosphere.
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.