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For comparison, the pelagic zone is the descriptive term for the ecological region above the benthos, including the water column up to the surface. At the other end of the spectrum, benthos of the deep ocean includes the bottom levels of the oceanic abyssal zone. [7]
The term benthos, coined by Haeckel in 1891, [3] comes from the Greek noun βένθος 'depth of the sea'. [1] [4] Benthos is used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as lakes, rivers, and streams. [5] There is also a redundant synonym, Benton. [6]
The BBL is generated by the friction of the water moving over the surface of the substrate, which decrease the water current significantly in this layer. [2] The thickness of this zone is determined by many factors, including the Coriolis force. The benthic organisms and processes in this boundary layer echo the water column above them. [2]
Filamentous cyanobacteria growing on an underwater surface. Phytobenthos (/. f aɪ t oʊ ˈ b ɛ n θ ɒ s /) (from Greek φυτόν (phyton, meaning "plants") and βένθος (benthos, meaning "depths") are autotrophic organisms found attached to bottom surfaces of aquatic environments, such as rocks, sediments, or even other organisms.
Macrobenthos consists of the organisms that live at the bottom of a water column [1] and are visible to the naked eye. [2] In some classification schemes, these organisms are larger than 1 mm; [1] in another, the smallest dimension must be at least 0.5 mm. [3] They include polychaete worms, pelecypods, anthozoans, echinoderms, sponges, ascidians, crustaceans.
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.
The offshore is divided into two further zones, an open water zone and a deep water zone. In the open water zone (or photic zone) sunlight supports photosynthetic algae and the species that feed upon them. In the deep water zone, sunlight is not available and the food web is based on detritus entering from the littoral and photic zones.
These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply [3] [4] and 90% of habitable space on Earth. [5] Seawater has an average salinity of 35 parts per thousand of water.