Kelp grows in underwater "forests" (kelp forests) in shallow oceans, and is thought to have appeared in Miocene, 23 to 5 million years ago. The organisms require nutrient-rich water with temperatures between 6 and 14 °C (43 and 57 °F). They are known for their high growth rate — the genera Macrocystis and Nereocystis can grow as fast as half a metre a day, ultimately reaching 30 to 80 metres (100 to 260 ft).
Through the 19th century, the word "kelp" was closely associated with seaweeds that could be burned to obtain soda ash (primarily sodium carbonate). The seaweeds used included species from both the orders Laminariales and Fucales. The word "kelp" was also used directly to refer to these processed ashes.
In most kelp, the thallus (or body) consists of flat or leaf-like structures known as blades. Blades originate from elongated stem-like structures, the stipes. The holdfast, a root-like structure, anchors the kelp to the substrate of the ocean. Gas-filled bladders (pneumatocysts) form at the base of blades of American species, such as Nereocystis lueteana (Mert. & Post & Rupr.) and keep the kelp blades close to the surface, holding up the blades by the gas they contain.
|Nutritional value per 100 g (3.5 oz)|
|Energy||180 kJ (43 kcal)|
|- Dietary fiber||1.3 g|
|Thiamine (vit. B1)||0.05 mg (4%)|
|Riboflavin (vit. B2)||0.15 mg (13%)|
|Niacin (vit. B3)||0.47 mg (3%)|
|Pantothenic acid (B5)||0.642 mg (13%)|
|Folate (vit. B9)||180 μg (45%)|
|Vitamin C||3 mg (4%)|
|Vitamin E||0.87 mg (6%)|
|Vitamin K||66 μg (63%)|
|Calcium||168 mg (17%)|
|Iron||2.85 mg (22%)|
|Magnesium||121 mg (34%)|
|Manganese||0.2 mg (10%)|
|Phosphorus||42 mg (6%)|
|Potassium||89 mg (2%)|
|Sodium||233 mg (16%)|
|Zinc||1.23 mg (13%)|
|Link to USDA Database entry
Percentages are relative to
US recommendations for adults.
Source: USDA Nutrient Database
Growth and reproduction 
Growth occurs at the base of the meristem, where the blades and stipe meet. Growth may be limited by grazing. Sea urchins, for example, can reduce entire areas to urchin barrens. The kelp life cycle involves a diploid sporophyte and haploid gametophyte stage. The haploid phase begins when the mature organism releases many spores, which then germinate to become male or female gametophytes. Sexual reproduction then results in the beginning of the diploid sporophyte stage, which will develop into a mature individual.
The parenchymatous thalli are generally covered with a mucilage layer, rather than cuticle.:226
Commercial uses 
Giant kelp can be harvested fairly easily because of its surface canopy and growth habit of staying in deeper water.
Bongo kelp ash is rich in iodine and alkali. In great amount, kelp ash can be used in soap and glass production. Until the Leblanc process was commercialized in the early 19th century, burning of kelp in Scotland was one of the principal industrial sources of soda ash (predominantly sodium carbonate). Alginate, a kelp-derived carbohydrate, is used to thicken products such as ice cream, jelly, salad dressing, and toothpaste, as well as an ingredient in exotic dog food and in manufactured goods. Alginate powder is also used frequently in general dentistry and orthodontics for making impressions of the upper and lower arches. These impressions are subsequently poured up in stone and the stone models are used in diagnosis and treatment 
Kombu (昆布 in Japanese, and 海带 in Chinese, Saccharina japonica and others), several Pacific species of kelp, is a very important ingredient in Chinese, Japanese, and Korean cuisines. Kombu is used to flavor broths and stews (especially dashi), as a savory garnish (tororo konbu) for rice and other dishes, as a vegetable, and a primary ingredient in popular snacks (such as tsukudani). Transparent sheets of kelp (oboro konbu) are used as an edible decorative wrapping for rice and other foods.
Kombu can be used to soften beans during cooking, and to help convert indigestible sugars and thus reduce flatulence.
Because of its high concentration of iodine, brown kelp (Laminaria) has been used to treat goiter, an enlargement of the thyroid gland caused by a lack of iodine, since medieval times.
In 2010, a group of researchers in the University of Newcastle found that a fibrous material called alginate in sea kelp was better at preventing fat absorption than most over-the-counter slimming treatments in laboratory trials. As a food additive, it may be used to reduce fat absorption and thus obesity.
As a possible renewable energy source 
Kelp has a high rate of growth and its decay is quite efficient in yielding methane, as well as sugars that can be converted to ethanol. It has been proposed that large open-ocean kelp farms could serve as a source of renewable energy. Unlike some biofuels such as corn ethanol, kelp energy avoids "food vs fuel" issues and does not require irrigation.
Kelp in history and culture 
During the Highland Clearances, many Scottish Highlanders were moved off their crofts, and went to industries such as fishing and kelping (producing soda ash from the ashes of kelp). At least until the 1820s, when there were steep falls in the price of kelp, landlords wanted to create pools of cheap or virtually free labour, supplied by families subsisting in new crofting townships. Kelp collection and processing was a very profitable way of using this labour, and landlords petitioned successfully for legislation designed to stop emigration. But the economic collapse of the kelp industry in northern Scotland led to further emigration, especially to North America.
In Chinese slang, "kelp" (simplified Chinese: 海带; traditional Chinese: 海帶; pinyin: hǎi dài), is used to describe an unemployed returnee. It has negative overtones, implying the person is drifting aimlessly, and is also a homophonic expression (Chinese: 海待; pinyin: hǎidài, literally "sea waiting"). This expression is contrasted with the employed returnee, having a dynamic ability to travel across the ocean: the "sea turtle" (simplified Chinese: 海龟; traditional Chinese: 海龜; pinyin: hǎi gūi).
Overfishing nearshore ecosystems leads to the degradation of kelp forests. Herbivores are released from their usual population regulation, leading to over-grazing of kelp and other algae. This can quickly result in barren landscapes where only a small number of species can thrive. Other major issues that threaten kelp include marine pollution and the quality of water, climate changes and certain invasive species.
A fish swimming in a Kelp Forest as seen at the Monterey Bay Aquarium.
A view of the Kelp Forest Exhibit at the Monterey Bay Aquarium from the upstairs level.
A close up view of Ecklonia maxima Giant Brown Kelp
Commercial kelp production in China 
Laminaria japonica, the important commercial seaweed, was first introduced into China in the late 1920s from Hokkaido, Japan. Commercial production of kelp harvested from its natural habitat took place in Japan for over a century. Yet mariculture of this algae on a very large commercial scale was realized in China only in the 1950s. Between the 1950s and the 1980s kelp production in China increased from about 60 to over 250,000 dry weight metric tons annually, making China the largest producer of Laminaria.
Prominent species 
- Bull-head kelp, Nereocystis luetkeana, a northwestern American species. Used by coastal indigenous peoples to create fishing nets.
- Giant kelp, Macrocystis pyrifera, the largest seaweed. Found in the Pacific coast of North America and South America.
- Kombu, Laminaria japonica and others, several edible species of kelp found in Japan.
Species of Laminaria in the British Isles;
- Laminaria digitata (Hudson) J.V. Lamouroux (Oarweed; Tangle)
- Laminaria hyperborea (Gunnerus) Foslie (Curvie)
- Laminaria ochroleuca Bachelot de la Pylaie
- Laminaria saccharina (Linnaeus) J.V.Lamouroux (sea belt; sugar kelp; sugarwack)
- Laminaria agardhii (NE. America)
- Laminaria angustata (Japan)
- Laminaria bongardina Postels et Ruprecht (Bering Sea to California)
- Laminaria cuneifolia (NE. America)
- Laminaria dentigera Klellm. (California - America)
- Laminaria digitata (NE. America)
- Laminaria ephemera Setchell (Sitka, Alaska, to Monterey County, California - America)
- Laminaria farlowii Setchell (Santa Cruz, California, to Baja California - America)
- Laminaria groenlandica (NE. America)
- Laminaria japonica (Japan), synonym of Saccharina japonica
- Laminaria longicruris (NE. America)
- Laminaria nigripes (NE. America)
- Laminaria ontermedia (NE. America)
- Laminaria pallida Greville ex J. Agardh (South Africa)
- Laminaria platymeris (NE. America)
- Laminaria saccharina (Linnaeus) Lamouroux (Aleutian Islands, Alaska to southern California America)
- Laminaria setchellii Silva (Aleutian Islands, Alaska to Baja California America)
- Laminaria sinclairii (Harvey ex Hooker f. ex Harvey) Farlow, Anderson et Eaton (Hope Island, British Columbia to Los Angeles, California - America)
- Laminaria solidungula (NE. America)
- Laminaria stenophylla (NE. America)
Other species in the Laminariales that may be considered as kelp:
- Alaria marginata Post. & Rupr. (Alaska and California - America)
- Costaria costata (C.Ag.) Saunders (Japan; Alaska, California - America)
- Ecklonia brevipes J. Agardh (Australia; New Zealand)
- Ecklonia maxima (Osbeck) Papenfuss (South Africa)
- Ecklonia radiata (C.Agardh) J. Agardh (Australia; Tasmania; New Zealand; South Africa)
- Eisenia arborea Aresch. (Vancouver Island, British Columbia, Montrey, Santa Catalina Island, California - America)
- Egregia menziesii (Turn.) Aresch.
- Hedophyllum sessile (C.Ag.) Setch (Alaska, California - America)
- Macrocystis angustifolia Bory (Australia; Tasmania and South Africa)
- Pleurophycus gardneri Setch. & Saund. (Alaska, California - America)
- Pterygophora californica Rupr. (Vancouver Island, British Columbia to Bahia del Ropsario, Baja California and California - America)
- Saccharina japonica (Japan)
Non-Laminariales species that may be considered as kelp:
- Durvillea antarctica, Fucales (New Zealand, South America, and Australia)
- Durvillea willana, Fucales (New Zealand)
- Durvillaea potatorum (Labillardière) Areschoug, Fucales (Tasmania; Australia)
Some animals are named after the kelp, either because they inhabit the same habitat as kelp or because they feed on kelp. These include:
- Northern kelp crab (Pugettia producta) and graceful kelp crab (Pugettia gracilis), Pacific coast of North America.
- Kelpfish (blenny) (e.g., Heterosticbus rostratus, genus Gibbonsia), Pacific coast of North America.
- Kelp goose (kelp hen) (Chloephaga hybrida), South America and the Falkland Islands
- Kelp pigeon (sheathbill) (Chionis alba and Chionis minor), Antarctic
See also 
- Migula, W. (1909). Kryptogamen-Flora von Deutschland, Deutsch-Österreich und der Schweiz. Band II. Algen. 2. Teil. Rhodophyceae, Phaeophyceae, Characeae. Gera: Verlag Friedriech von Zezschwitz. pp. i–iv, 1–382, 122 (41 col.) pls.
- Macrocystis Evolution
- Thomas, D. 2002. Seaweeds. The Natural History Museum, London, p. 15. ISBN 0-565-09175-1
- "Kelp," in Oxford English Dictionary (Second Edition). Oxford University Press, 1989. Retrieved 1 December 2006
- Fritsch, F. E. (1945). Structure and Reproduction of the Algae, Volume 2. Cambridge University Press. p. 939. ISBN 9780521050425. OCLC 223742770.
- Clow, Archibald and Clow, Nan L. (1952). Chemical Revolution. Ayer Co Pub, June 1952, pp. 65–90. ISBN 0-8369-1909-2
- Powers, John M. Powers. Craig's Restorative Dental Materials, 12th Edition. C.V. Mosby, 022006. p. 270
- Kazuko, Emi: Japanese Cooking, p. 78, Hermes House, 2002, p. 78. ISBN 0-681-32327-2
- Graimes, Nicola: The Best-Ever Vegetarian Cookbook, Barnes & Noble Books, 1999, p. 59. ISBN 0-7607-1740-0
- Iodine Helps Kelp Fight Free Radicals and May Aid Humans, Too Newswise, Retrieved on July 8, 2008.
- "Is Seaweed The Answer To A Dieter's Prayer?". Sky News. March 22, 2010. Retrieved March 23, 2010.
- Christiansen, Ryan C. (2008-10-31). "British report: Use kelp to produce energy". Biomassmagazine.com. Retrieved 2013-02-12.
-  allwords.com definition for "Kelper",
-  dictionary.com definition for "Kelper"
- Dayton, P.K. 1985a. Ecology of kelp communities. Annual Review of Ecology and Systematics 16: 215-245.
- Sala, E., C.F. Bourdouresque and M. Harmelin-Vivien. 1998. Fishing, trophic cascades, and the structure of algal assemblages: evaluation of an old but untested paradigm. Oikos 82: 425-439.
- Planet, Team (2012-01-12). "Green Glossary: Kelp Forests: Other Marine Life: Animal Planet". Animals.howstuffworks.com. Retrieved 2013-02-12.
- AlgaeBase Laminariales
Further reading 
- Druehl, L.D. 1988. Cultivated edible kelp. in Algae and Human Affairs. Lembi, C.A. and Waaland, J.R. (Editors) 1988.ISBN 0 521 32115 8.
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