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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]
Water flow can determine the types and distributions of phytobenthos, especially in the stream communities where the water is constantly moving. [1] Rivers with more steady flow contribute to the stable environment that can promote the growth of phytobenthos communities.
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.
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]
The principal factor controlling the distribution of aquatic plants is the availability of water. However, other abiotic factors may also control their distribution including nutrient availability, availability of carbon dioxide and oxygen, water temperature, characteristics of the substrate, water transparency, [14] water movement, and salinity. [6]
Meiobenthos, also called meiofauna, are small benthic invertebrates that live in marine or freshwater environments, or both.The term meiofauna loosely defines a group of organisms by their size—larger than microfauna but smaller than macrofauna—rather than by their taxonomy.
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.