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Kelp

Article Discussion

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Kelps are large brown algae or seaweeds that make up the order Laminariales. There are about 30 different genera.<ref name="HMR">Template:Cite journal</ref> Despite its appearance and use of photosynthesis in chloroplasts, kelp is technically not a plant but a stramenopile (a group containing many protists).<ref name="BioOne">Template:Cite journal</ref>

Kelp grow from stalks close together in very dense areas like forests under shallow temperate and Arctic oceans.<ref name="HMR"/> They were previously thought to have appeared in the Miocene, 5 to 23 million years ago based on fossils from California.<ref>University of California Museum of Paleontology: The Miocene Epoch</ref> New fossils of kelp holdfasts from early Oligocene rocks in Washington State show that kelps were present in the northeastern Pacific Ocean by at least 32 million years ago.<ref>Kiel, S., J.L. Goedert, T.L. Huynh, M. Krings, D. Parkinson, R. Romero, C.V. Looy. 2024. Early Oligocene kelp holdfasts and stepwise evolution of the kelp ecosystem in the North Pacific. PNAS 121: e2317054121</ref> The organisms require nutrient-rich water with temperatures between Template:Convert. They are known for their high growth rate—the genera Macrocystis and Nereocystis can grow as fast as half a metre a day (that is, about 20 inches a day), ultimately reaching Template:Convert.<ref name="Thomas-2002">Thomas, D. 2002. Seaweeds. The Natural History Museum, London, p. 15. Template:ISBN</ref>

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.<ref>"Kelp," in Oxford English Dictionary (Second Edition). Oxford University Press, 1989. Retrieved 1 December 2006</ref>

DescriptionEdit

File:Chowiet Island beach kelp.jpg
Alaskan beach kelp

The thallus (or body) consists of flat or leaf-like structures known as lamina (or blades) that originate from elongated stem-like structures, referred to as the stipes. A root-like structure (called the holdfast) 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, to hold the kelp blades close to the surface to access light for photosynthesis.(Mert. & Post & Rupr.)<ref name="Thomas-2002" /> The stipes are generally covered with a slimy mucilage layer, rather than a waxy cuticle.<ref>Template:Cite book</ref>

Growth and reproductionEdit

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 ecosystems to kelp-less wastelands known as urchin barrens.<ref>Norderhaug, KM., Christie, H. 2009. Sea urchin grazing and kelp re-vegetation in the NE Atlantic. Marine Biology Research 5: 515-528. Estuarine, Coastal and Shelf Science 95: 135-144</ref> 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.

TaxonomyEdit

PhylogenyEdit

Seaweed were generally considered homologues of terrestrial plants,<ref>Darwin, C. The Voyage of the Beagle; P. F. Collier & Son Corporation: New York, 1860</ref> but are only very distantly related to plants, and have evolved plant-like structures through convergent evolution.<ref name="Drobnitch-2015">Template:Cite journal</ref> Where plants have leaves, stems, and reproductive organs, kelp have independently evolved blades, stipes, and sporangia. With radiometric dating and the measure Ma “unequivocal minimum constraint for total group Pinaceae” vascular plants have been measured as having evolved around 419–454 Ma<ref>Template:Cite journal</ref> while the ancestors of Laminariales are much younger at 189 Ma.<ref>Template:Cite journal</ref> Although these groups are distantly related as well as different in evolutionary age, there are still comparisons that can be made between the structures of terrestrial plants and kelp but in terms of evolutionary history, most of these similarities come from convergent evolution.

Some kelp species including giant kelp, have evolved transport mechanisms for organic as well as inorganic compounds,<ref>Template:Cite journal</ref> similar to mechanisms of transport in trees and other vascular plants. In kelp this transportation network uses trumpet-shaped sieve elements (SEs). A 2015 study aimed to evaluate the efficiency of giant kelp (Macrocystis pyrifera) transport anatomy looked at 6 different laminariales species to see if they had typical vascular plant allometric relationships (if SEs had a correlation with the size of an organism). Researchers expected to find the kelp’s phloem to work similarly to a plant's xylem and therefore display similar allometric trends to minimize pressure gradient. The study found no universal allometric scaling between all tested structures of the laminariales species which implies that the transport network of brown algae is only just beginning to evolve to efficiently fit their current niches.<ref name="Drobnitch-2015" />

Apart from undergoing convergent evolution with plants, species of kelp have undergone convergent evolution within their own phylogeny that has led to niche conservatism.<ref name="Starko-2020">Template:Cite journal</ref> This niche conservatism means that some species of kelp have convergently evolved to share similar niches, as opposed to all species diverging into distinct niches through adaptive radiation. A 2020 study looked at functional traits (blade mass per area, stiffness, strength, etc.) of 14 species of kelp and found that many of these traits evolved convergently across kelp phylogeny. With different species of kelp filling slightly different environmental niches, specifically along a wave disturbance gradient, many of these convergently evolved traits for structural reinforcement also correlate with distribution along that gradient. The wave disturbance gradient that this study refers to is the environments that this kelp inhabit have a varied level of perturbation from the tide and waves that pull at the kelp. It can be assumed from these results that niche partitioning along wave disturbance gradients is a key driver of divergence between closely related kelp.<ref name="Starko-2020" />

Due to the often varied and turbulent habitat that kelp populate, plasticity of certain structural traits has been a key for the evolutionary history of the phyla. Plasticity helps with a very important aspect of kelp adaptations to ocean environments, and that is the unusually high levels of morphological homoplasy between lineages. This in fact has made classifying brown algae difficult.<ref>Template:Cite journal</ref> Kelp often have similar morphological features to other species within its own area since the roughness of the wave disturbance regime, but can look fairly different from other members of its own species that are found in different wave disturbance regimes. Plasticity in kelps most often involves blade morphology such as the width, ruffle, and thickness of blades.<ref name="Koehl-2008">Template:Cite journal</ref> Just one example is the giant bull kelp Nereocystis luetkeana, which have evolved to change blade shape in order to increase drag in water and interception of light when exposed to certain environments. Bull kelp are not unique in this adaptation; many kelp species have evolved a genetic plasticity for blade shapes for different water flow habitats. So individuals of the same species will have differences to other individuals of the same species due to what habitat they grow in.<ref>Lobban, C. S., Wynne, M. J., & Lobban. (1981). The Biology of Seaweeds. University of California Press.</ref> Many species have different morphologies for different wave disturbance regimes<ref name="Koehl-2008" /> but giant kelp Macrocystis integrifolia has been found to have plasticity allowing for 4 distinct types of blade morphology depending on habitat.<ref>Template:Cite journal</ref> Where many species only have two or three different blade shapes for maximizing efficiency in only two or three habitats. These different blade shapes were found to decrease breakage and increase ability to photosynthesize. Blade adaptations like these are how kelp have evolved for efficiency in structure in a turbulent ocean environment, to the point where their stability can shape entire habitats. Apart from these structural adaptations, the evolution of dispersal methods relating to structure have been important for the success of kelp as well.

Kelp have had to adapt dispersal methods that can make successful use of ocean currents. Buoyancy of certain kelp structures allows for species to disperse with the flow of water.<ref>Template:Cite journal</ref> Certain kelp form kelp rafts, which can travel great distances away from the source population and colonize other areas. The bull kelp genus Durvillaea includes six species, some that have adapted buoyancy and others that have not. Those that have adapted buoyancy have done so thanks to the evolution of a gas filled structure called the pneumatocysts which is an adaptation that allows the kelp to float higher towards the surface to photosynthesize and also aids in dispersal by floating kelp rafts.<ref>Template:Cite journal</ref> For Macrocystis pyrifera, adaptation of pneumatocysts and raft forming have made the species dispersal method so successful that the immense spread of coast in which the species can be found has been found to actually be very recently colonized. This can be observed by the low genetic diversity in the subantarctic region.<ref>Template:Cite journal</ref> Dispersal by rafts from buoyant species also explains some evolutionary history for non-buoyant species of kelp. Since these rafts commonly have hitchhikers of other diverse species, they provide a mechanism for dispersal for species that lack buoyancy. This mechanism has been recently confirmed to be the cause of some dispersal and evolutionary history for kelp species in a study done with genomic analysis.<ref>Template:Cite journal</ref> Studies of kelp structure evolution have helped in the understanding of the adaptations that have allowed for kelp to not only be extremely successful as a group of organisms but also successful as an ecosystem engineer of kelp forests, some of the most diverse and dynamic ecosystems on earth.

Prominent speciesEdit

Species of Laminaria in the British Isles;

Species of Laminaria worldwide, listing of species at AlgaeBase:<ref>AlgaeBase Laminariales</ref>

File:Five-ribbed kelp (Costaria costata).jpg
Costaria costata, five-ribbed kelp

Other species in the Laminariales that may be considered as kelp:

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Non-Laminariales species that may be considered as kelp:

File:KelpforestI2500ppx.JPG
A kelp forest
File:Anemone and seastar in kelp forest.jpg
Anemone and seastar in kelp forest

EcologyEdit

Kelp forestsEdit

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Kelp may develop dense forests with high production,<ref>Template:Cite journal</ref><ref>Abdullah, M.I., Fredriksen, S., 2004. Production, respiration and exudation of dissolved organic matter by the kelp Laminaria hyperborea along the west coast of Norway. Journal of the Marine Biological Association of the UK 84: 887.</ref> biodiversity and ecological function. Along the Norwegian coast these forests cover 5,800 km2,<ref>Rinde, E., 2009. Dokumentasjon av modellerte marine Naturtyper i DNs Naturbase. Førstegenerasjonsmodeller til kommunenes startpakker for kartlegging av marine naturtyper 2007. NIVA report, 32 pp.</ref> and they support large numbers of animals.<ref name="Christie-2003">Christie, H., Jørgensen, N.M., Norderhaug, K.M., Waage-Nielsen, E., 2003. Species distribution and habitat exploitation of fauna associated with kelp (Laminaria hyperborea) along the Norwegian coast. Journal of the Marine Biological Association of the UK 83, 687-699.</ref><ref>Jørgensen, N.M., Christie, H., 2003. l Diurnal, horizontal and vertical dispersal of kelp associated fauna. Hydrobiologia 50, 69-76.</ref> Numerous sessile animals (sponges, bryozoans and ascidians) are found on kelp stipes and mobile invertebrate fauna are found in high densities on epiphytic algae on the kelp stipes and on kelp holdfasts.<ref>Norderhaug, K.M., Christie, H., Rinde, E., 2002. Colonisation of kelp imitations by epiphyte and holdfast fauna; a study of mobility patterns. Marine Biology 141, 965-973.</ref> More than 100,000 mobile invertebrates per square meter are found on kelp stipes and holdfasts in well-developed kelp forests.<ref name="Christie-2003" /> While larger invertebrates and in particular sea urchins (Strongylocentrotus droebachiensis) are important secondary consumers controlling large barren ground areas on the Norwegian coast, they are scarce inside dense kelp forests.<ref>Norderhaug, K.M., Christie, H., 2009. Sea urchin grazing and kelp re-vegetation in the NE Atlantic. Marine Biology Research 5, 515-528.</ref>

InteractionsEdit

Some animals are named after the kelp, either because they inhabit the same habitat as kelp or because they feed on kelp. These include:

ConservationEdit

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.<ref name="Dayton 1985a">Dayton, P.K. 1985a. Ecology of kelp communities. Annual Review of Ecology and Systematics 16: 215-245.</ref><ref name="Sala1998">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.</ref> Other major factors which threaten kelp include marine pollution and the quality of water, climate changes and certain invasive species.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Kelp forests are some of the most productive ecosystems in the world - they are home to a great diversity of species. Many groups, like those at the Seattle Aquarium, are studying the health, habitat, and population trends in order to understand why certain kelp (like bull kelp) thrives in some areas and not others. Remotely Operated Vehicles are used in the surveying of sites and the data extracted is used to learn about which conditions are best suited for kelp restoration. <ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

UsesEdit

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Template:Nutritional value

Giant kelp can be harvested fairly easily because of its surface canopy and growth habit of staying in deeper water.

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).<ref name="Clow 52">Template:Cite book</ref> Around 23 tons of seaweed was required to produce 1 ton of kelp ash. The kelp ash would consist of around 5% sodium carbonate.<ref>Jonathan Pereira, Fred B. Kilmer, The Elements of Materia Medica and Therapeutics, Volume 1, 1854, p. 558</ref>

Once the Leblanc Process became commercially viable in Britain during the 1820s, common salt replaced kelp ash as raw material for sodium carbonate. Though the price of kelp ash went into steep decline, seaweed remained the only commercial source of iodine. To supply the new industry in iodine synthesis, kelp ash production continued in some parts of West and North Scotland, North West Ireland and Guernsey. The species Saccharina latissima yielded the greatest amount of iodine (between 10 and 15 lbs per ton) and was most abundant in Guernsey. Iodine was extracted from kelp ash using a lixiviation process.<ref>Edward C. C. Stanford, Wentworth L. Scott, ‘The Economic Applications of Seaweed’, February 14, 1862, Journal of the Royal Society of Arts, Vol 10, No. 482, 185-199</ref> As with sodium carbonate however, mineral sources eventually supplanted seaweed in iodine production.<ref>John J. McKetta Jr. Taylor & Francis, Encyclopaedia of Chemical Processing and Design: Volume 27 - Hydrogen Cyanide to Ketones Dimethyl (Acetone), 1988, p. 283</ref>

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.<ref>Template:Cite book</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Alginate powder is also used frequently in general dentistry and orthodontics for making impressions of the upper and lower arches.<ref>Powers, John M. Powers. Craig's Restorative Dental Materials, 12th Edition. C.V. Mosby, 022006. p. 270</ref> Kelp polysaccharides are used in skin care as gelling ingredients and because of the benefits provided by fucoidan.Template:Citation needed

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.<ref>Kazuko, Emi: Japanese Cooking, p. 78, Hermes House, 2002, p. 78. Template:ISBN</ref>

Kombu can be used to soften beans during cooking, and to help convert indigestible sugars and thus reduce flatulence.<ref>Graimes, Nicola: The Best-Ever Vegetarian Cookbook, Barnes & Noble Books, 1999, p. 59. Template:ISBN</ref>

File:Morskaja-kapusta.jpg
Saccharina latissima in canned salad form

In Russia, especially in the Russian Far East, and former Soviet Union countries several types of kelp are of commercial importance: Saccharina latissima, Laminaria digitata, Saccharina japonica. Known locally as "Sea Cabbage" (Морская капуста in Russian), it comes in retail trade in dried or frozen, as well as in canned form and used as filler in different types of salads, soups and pastries.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref>Iodine Helps Kelp Fight Free Radicals and May Aid Humans, Too Newswise, Retrieved on July 8, 2008.</ref> An intake of roughly 150 micrograms of iodine per day is beneficial for preventing hypothyroidism. Overconsumption can lead to kelp-induced thyrotoxicosis.<ref>Template:Cite journal</ref>

In 2010, researchers found that alginate, the soluble fibre substance 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Kelp in its natural form has not yet been demonstrated to have such effects.

Kelp's rich iron content can help prevent iron deficiency.<ref>Template:Cite journal</ref>

Commercial productionEdit

Commercial production of kelp harvested from its natural habitat has taken place in Japan for over a century. Many countries today produce and consume laminaria products; the largest producer is China. Laminaria japonica, the important commercial seaweed, was first introduced into China in the late 1920s from Hokkaido, Japan. Yet mariculture of this alga 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.

In cultureEdit

File:Scuba diver in kelp forest.jpg
Scuba diver in kelp forest

Some of the earliest evidence for human use of marine resources, coming from Middle Stone Age sites in South Africa, includes the harvesting of foods such as abalone, limpets, and mussels associated with kelp forest habitats.

In 2007, Erlandson et al. suggested that kelp forests around the Pacific Rim may have facilitated the dispersal of anatomically modern humans following a coastal route from Northeast Asia to the Americas. This "kelp highway hypothesis" suggested that highly productive kelp forests supported rich and diverse marine food webs in nearshore waters, including many types of fish, shellfish, birds, marine mammals, and seaweeds that were similar from Japan to California, Erlandson and his colleagues also argued that coastal kelp forests reduced wave energy and provided a linear dispersal corridor entirely at sea level, with few obstacles to maritime peoples. Archaeological evidence from California's Channel Islands confirms that islanders were harvesting kelp forest shellfish and fish, beginning as much as 12,000 years ago.

During the Highland Clearances, many Scottish Highlanders were moved on to areas of estates known as crofts, and went to industries such as fishing and kelping (producing soda ash from the ashes of kelp). At least until the 1840s, 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. The profitability of kelp harvesting meant that landlords began to subdivide their land for small tenant kelpers, who could now afford higher rent than their gentleman farmer counterparts.<ref>J. M. Bumsted, The People's Clearance: Highland Emigration to British North America, 1770-1815, 1981</ref> But the economic collapse of the kelp industry in northern Scotland during the 1820s led to further emigration, especially to North America.Template:Citation needed

Natives of the Falkland Islands are sometimes nicknamed "Kelpers".<ref>[1] allwords.com definition for "Kelper",</ref><ref>[2] dictionary.com definition for "Kelper"</ref> This designation is primarily applied by outsiders rather than the natives themselves.

In Chinese slang, "kelp" (Template:Zh), is used to describe an unemployed returnee.Template:Clarify It has negative overtones, implying the person is drifting aimlessly, and is also a homophonic expression (Template:Zh, literally "sea waiting"). This expression is contrasted with the employed returnee, having a dynamic ability to travel across the ocean: the "sea turtle" (Template:Zh) and is also homophonic with another word (Template:Zh, literally "sea return").

GalleryEdit

  • Giant kelp (Macrocystis pyrifera) 01.jpg

    Giant kelp in Monterey Bay Aquarium's Kelp Forest exhibit

  • Blue Rockfish in kelp forest.jpg

    Blue rockfish in kelp forest

  • Kelp forest-blue.jpg

    An underwater shot of a kelp forest

  • CLOSE UP OF ECKLONIA MAXIMA LEAF.jpg

    A close up view of Ecklonia maxima, giant brown kelp

  • Kelpwik.jpg

    Washed-up kelp found along the coast of La Jolla Shores

  • Kelp by Gustavo Gerdel.jpg

    Scuba diving in a kelp forest in California

See alsoEdit

ReferencesEdit

Template:Reflist

Further readingEdit

  • Druehl, L.D. 1988. Cultivated edible kelp. in Algae and Human Affairs. Lembi, C.A. and Waaland, J.R. (Editors) 1988.Template:ISBN.
  • Erlandson, J.M., M.H. Graham, B.J. Bourque, D. Corbett, J.A. Estes, & R.S. Steneck. 2007. The Kelp Highway hypothesis: marine ecology, the coastal migration theory, and the peopling of the Americas. Journal of Island and Coastal Archaeology 2:161-174.
  • Eger, A. M., Layton, C., McHugh, T. A, Gleason, M., and Eddy, N. (2022). Kelp Restoration Guidebook: Lessons Learned from Kelp Projects Around the World. The Nature Conservancy, Arlington, VA, USA.

External linksEdit

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