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The shells of dead diatoms can reach as much as a half-mile (800 m) deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Depression, which was once made up of a system of fresh-water lakes.
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Diatomite rock sample from Sisquoc Formation Scanning electron micrograph of diatomaceous earth. Diatomaceous earth (/ ˌ d aɪ. ə t ə ˈ m eɪ ʃ ə s / DY-ə-tə-MAY-shəs), also known as diatomite (/ d aɪ ˈ æ t ə m aɪ t / dy-AT-ə-myte), celite, or kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder.
Diatoms are enclosed in protective silica (glass) shells called frustules. Each frustule is made from two interlocking parts covered with tiny holes through which the diatom exchanges nutrients and wastes. [156] The frustules of dead diatoms drift to the ocean floor where, over millions of years, they can build up as much as half a mile deep. [160]
As new species of diatoms evolved and spread, oceanic silica levels began to decrease. [19] Today, there are an estimated 100,000 species of diatoms, most of which are microscopic (2-200 μm). [19] Some early diatoms were larger, and could be between 0.2 and 22mm in diameter. [17]
These patterns are composed of a series of transverse lines (known as striae) that can appear as rows of dots when viewed with an optical microscope. Some pennate diatoms also exhibit a fissure along their longitudinal axis. This is known as a raphe, and is involved in gliding movements made by diatom cells; motile diatoms always possess a raphe.
Chaetoceros is a genus of diatoms in the family Chaetocerotaceae, first described by the German naturalist C. G. Ehrenberg in 1844. [1] Species of this genus are mostly found in marine habitats, but a few species exist in freshwater. [2] It is arguably the common and most diverse genus of marine planktonic diatoms, [3] with over 200 accepted ...