Macrocystis is a monospecific genus[3] of kelp (large brown algae) with all species now synonymous with Macrocystis pyrifera. It is commonly known as giant kelp or bladder kelp. This genus contains the largest of all the phaeophyceae or brown algae. Macrocystis has pneumatocysts at the base of its blades. Sporophytes are perennial and the individual may live for up to three years;[4] stipes/fronds within a whole individual undergo senescence, where each frond may persist for approximately 100 days.[5] The genus is found widely in subtropical, temperate, and sub-Antarctic oceans of the Southern Hemisphere (e.g. Chile, New Zealand, Australia, Falkland Islands, Auckland Islands, etc.) and in the northeast Pacific from Baja California to Sitka, Alaska. Macrocystis is often a major component of temperate kelp forests.
Despite its appearance, it is not a plant; it is a heterokont. Giant kelp is common along the coast of the northeastern Pacific Ocean, from Baja California north to southeast Alaska, and is also found in the southern oceans near South America, South Africa, Australia, and New Zealand. Individual algae may grow to more than 45 metres (150 feet) long at a rate of as much as 60 cm (2 ft) per day. Giant kelp grows in dense stands known as kelp forests, which are home to many marine animals that depend on the algae for food or shelter. The primary commercial product obtained from giant kelp is alginate, but humans also harvest this species on a limited basis for use directly as food, as it is rich in iodine, potassium, and other minerals. It can be used in cooking in many of the ways other sea vegetables are used, and particularly serves to add flavor to bean dishes.
Macrocystis is a monospecific genus, the sole species is M. pyrifera. Some individuals are so huge that the thallus may grow to up to 60 m (200 ft).[6] The stipes arise from a holdfast and branch three or four times from near the base. Blades develop at irregular intervals along the stipe.[7][8] M. pyrifera grows to over 45 m (150 ft) long.[8][9] The stipes are unbranched and each blade has a gas bladder at its base.[10]
Macrocystis pyrifera is the largest of all algae. The stage of the life cycle that is usually seen is the sporophyte, which is perennial and individuals persist for many years. Individuals may grow to up to 50 m (160 ft) long or more. The kelp often grows even longer than the distance from the bottom to the surface as it will grow in a diagonal direction due to the ocean current pushing against the kelp.[11]: 201 The stalks arise from a basal meristem, with as many as 60 stalks in older well protected plants.[12] Blades develop at irregular intervals along the stipe, with a single pneumatocyst (gas bladder) at the base of each blade.[10] At the base of each stalk a cluster of blades that lack pneumatocysts, instead they develop small sacks on the blade that release the biflagellated zoospores these are the sporophylls.[12]
The smaller morphs, formerly identified as Macrocystis integrifolia, have deep brown color on flattened rhizomes which are profusely dichotomously branched. Each is attached by branched root-like structures coming out of the sides of the rhizomes. Slender main stipes (about 1 centimetre (0.39 in) wide to 30 metres (98 ft) long) come from the rhizome which is up to 0.1 metres (3.9 in) at the widest. Periodically 5 centimetres (2.0 in) wide and 35 centimetres (14 in) long flattened leaf-like branches derive from the stipe. They have furrowed surfaces and taper gradually, but then have an oval or rounded float where attached to the stipe. The blade-like branches have notched denticulate edges leading to the terminal blade at the tip of the stipe, which is separated by several smaller branches.[13] It grows to only 6 m (20 ft) long. It is found on intertidal rocks or shallow subtidal rocks along the Pacific coast of North America (British Columbia to California) and South America.[8][14] In New Zealand M. pyrifera is found in the subtidal zone of southern North Island, the South Island, Chatham, Stewart, Bounty, Antipodes, Auckland and Campbell Islands.[15] The species can be found on rock and on sheltered open coasts.[15]
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M. pyrifera growing in the Channel Islands
Macrocystis integrifolia
Giant kelp
The macroscopic sporophyte has many specialized blades growing near the holdfast. These blades bear various sori containing sporangia, which release haploid spores, which will grow into microscopic female and male gametophytes. These gametophytes, after reaching the appropriate substrata, grow mitotically to eventually produce gametes.[16]
Females release their eggs (oogonia) along with a pheromone, the lamoxirene.[17][18] This compound triggers sperm release by males. The Macrocystis sperm consists of biflagellate non-synthetic antherozoids, which find their way to the oogonia following the lamoxirene. The egg is then fertilized to form the zygote, which, through mitosis, begins growth.
Macrocystis integrifolia is found on intertidal rocks or shallow subtidal rocks along the Pacific coast of North America from British Columbia to California.[1][19][20] It prefers water about 7 metres (23 ft) to 10 metres (33 ft) deep and exposed to the open sea and normal salinities, yet sheltered from full wave action.[21]
Macrocystis integrifolia alternates heteromorphic phases from a macroscopic sporophyte to dioecious microscopic gametophytes.[20] It has been studied as a plant fertilizer, increasing bean yields up to 24% and chemical studies indicate presence of phytohormone-like substances.[22]
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Macrocystis pyrifera is one of the fastest-growing organisms on Earth.[23][24]: 8 They can grow at a rate of 60 cm (2 ft) a day to reach over 45 m (150 ft) long in one growing season.[8][25][26]
Juvenile giant kelp grow directly upon their parent female gametophyte. To establish itself, a young kelp produces one or two primary blades, and begins a rudimentary holdfast, which serves to anchor the plant to the rocky bottom. As the kelp grows, additional blades develop from the growing tip, while the holdfast enlarges and may entirely cover the rock to which it is attached.
Growth occurs with lengthening of the stipe (central stalk), and splitting of the blades. At the growing tip is a single blade, at the base of which develop small gas bladders along one side. As the bladders and stipe grow, small tears develop in the attached blade. Once the tears have completed, each bladder supports a single separate blade along the stipe, with the bladders and their blades attached at irregular intervals.[7][27]: 226–227
Macrocystis typically grow forming extensive beds, large "floating canopies", on rocky substrata between the low intertidal.[8][16] It was harvested by barges which used large blades to harvest up to 300 tons a day along the coast of California.[28]
Macrocystis pyrifera is found in North America (Alaska to California), South America, South Africa, New Zealand, and southern Australia.[29] It thrives in cooler waters where the ocean water temperature remains mostly below 21 °C (70 °F).[26] The species is also found near Tristan da Cunha in the Mid-South Atlantic Ocean.
Where the bottom is rocky and affords places for it to anchor, giant kelp forms extensive kelp beds with large "floating canopies".[8] When present in large numbers, giant kelp forms kelp forests that are home to many marine species that depend upon the kelp directly for food and shelter, or indirectly as a hunting ground for prey. Both the large size of the kelp and the large number of individuals significantly alter the availability of light, the flow of ocean currents, and the chemistry of the ocean water in the area where they grow.[30]: 158
In high-density populations, giant kelp individuals compete with other individuals of the species for space and resources. Giant kelp may also compete with Pterygophora californica in these circumstances.[31][32]
Where surface waters are poor in nutrients, nitrogen in the form of amino acids is translocated up the stipe through sieve elements that very much resemble the phloem of vascular plants.[30]: 151–153 [11]: 204 Translocation of nutrients along the stipe may be as rapid as 60 cm (24 in) per hour.[27] Most translocation occurs to move carbon-rich photosynthate, and typically transfers material from mature regions to actively growing regions where the machinery of photosynthesis is not yet fully in place. Translocation also moves nutrients downward from light-exposed surface fronds to sporophylls (reproductive fronds) at the base of the kelp, where there is little light and thus little photosynthesis to produce food.
Initially, 17 species were described within the genus Macrocystis.[33] In 1874, Hooker, following blade morphology, put them all under the same taxon, Macrocystis pyrifera.[34] In modern times, the large number of species were re-classified based on the holdfast morphology, which distinguished three species (M. angustifolia, M. integrifolia, and M. pyrifera) and on blade morphology, which added a fourth species (M. laevis) in 1986.[35] In 2009 and 2010, however, two studies that used both morphological[36] and molecular[3] assessments demonstrate that Macrocystis is monospecific (as M. pyrifera), which is currently accepted by the phycological community (see AlgaeBase).[37]
Although Macrocystis is a monospecific genus, some split it into the four morphs, or sub-species, described below, following pre-2010 taxonomy:[38][39]
Macrocystis is distributed along the eastern Pacific coast from Alaska to Mexico and from Peru and along the Argentinian coast as well as in Australia, New Zealand, South Africa and most sub-Antarctic islands to 60°S.[16]
Macrocystis pyrifera has been utilized for many years as a food source;[44][45] it also contains many compounds such as iodine, potassium, other minerals vitamins and carbohydrates and thus has also been used as a dietary supplement.[46][47]: 58 In the beginning of the 20th century California kelp beds were harvested as a source for soda ash.[44][48][49] With commercial interest increasing significantly during the 1970s and the 1980s this was primarily due to the production of alginates, and also for biomass production for animal feed due to the energy crisis during that period.[48][49] However the commercial production of M. pyrifera never became reality. With the end of the energy crisis and the decline in prices of alginates, the research into farming Macrocystis also declined.[45]
The demand for M. pyrifera is increasing due to the newfound uses of these plants such as fertilizers, cultivation for bioremediation purposes, abalone and sea urchin feed.[45] There is current research going into utilizing M. pyrifera as feed for other aquaculture species such as shrimps.[50] Recently, M. pyrifera has been examined as a possible feedstock for conversion into ethanol for biofuel use.[51]
In recent years, the kelp forests have decreased dramatically throughout Japan, Chile, Korea, Australia and North America.[52] Harvesting of kelp as a food source and other uses may be the least concerning aspect to its depletion. In the Northwest Pacific kelp forests in waters near large population centres may be most affected by the sewer/stormwater discharge.[53]
The natural phenomenon known as El Niño cycles warm, tropical water from the South Pacific to Northern waters. This has been known to kill off M. pyrifera, due to its need for cold waters it would usually find in the North Pacific Ocean.[54] In California, El Niño also brought along a population bloom of purple sea urchins which feed on the giant kelp.[55] By the late 2000s most of the onshore giant kelp in California was practically nonexistent.
Off the coast of Tasmania, kelp forests have been significantly affected by several factors, including warming waters, shifting of the East Australian current (EAC), and invasion of long-spine sea urchins. Locals have noticed significant effects on the population of abalone, a food source for the Aboriginal Tasmanians for thousands of years. These changes have also affected the oyster farming industry. By saving oysters that have survived disease outbreaks, they have been able to continue their way of life.[56] It was estimated that by 2019, 95 per cent of the giant kelp forests along Tasmania's east coast had been lost within just a few decades.[57] Some of this loss was attributed by locals to the harvesting of the forests by Alginates Australia, which opened its factory near Triabunna in 1963, shutting down operations 10 years later as uneconomical. However, expert in marine ecosystems Craig Johnson says that the loss of the forests "is almost certainly the result of climate change". Water temperatures along the east coast of Tasmania have been rising at nearly four times the average rate globally. The EAC brings warmer waters, which are also nutrient-poor compared to the previously usual cold water around the coast. Common kelp (Ecklonia radiata) is better at nitrogen storage than giant kelp, so has been taking over the areas formerly occupied by giant kelp.[58]
Macrocystis pyrifera has become Australia’s first federally-listed endangered marine community.[58][59] Scientists and conservationists are continuously looking into ways to restore the once heavily populated species to its original state. Methods include artificial reefs, reducing numbers of purple sea urchins in overpopulated areas, and planting roots along the ocean floor.[52] Scientists had built 28 artificial reefs off Maria Island by 2019, and were hopeful of bringing the kelp forests back.[57]
{{cite web}}: CS1 maint: url-status (link) Macrocystis is a monospecific genus of kelp (large brown algae) with all species now synonymous with Macrocystis pyrifera. It is commonly known as giant kelp or bladder kelp. This genus contains the largest of all the phaeophyceae or brown algae. Macrocystis has pneumatocysts at the base of its blades. Sporophytes are perennial and the individual may live for up to three years; stipes/fronds within a whole individual undergo senescence, where each frond may persist for approximately 100 days. The genus is found widely in subtropical, temperate, and sub-Antarctic oceans of the Southern Hemisphere (e.g. Chile, New Zealand, Australia, Falkland Islands, Auckland Islands, etc.) and in the northeast Pacific from Baja California to Sitka, Alaska. Macrocystis is often a major component of temperate kelp forests.
Despite its appearance, it is not a plant; it is a heterokont. Giant kelp is common along the coast of the northeastern Pacific Ocean, from Baja California north to southeast Alaska, and is also found in the southern oceans near South America, South Africa, Australia, and New Zealand. Individual algae may grow to more than 45 metres (150 feet) long at a rate of as much as 60 cm (2 ft) per day. Giant kelp grows in dense stands known as kelp forests, which are home to many marine animals that depend on the algae for food or shelter. The primary commercial product obtained from giant kelp is alginate, but humans also harvest this species on a limited basis for use directly as food, as it is rich in iodine, potassium, and other minerals. It can be used in cooking in many of the ways other sea vegetables are used, and particularly serves to add flavor to bean dishes.
Macrocystis est un genre d'algues brunes de la famille des Laminariaceae. Les thalles atteignent les 45 mètres de longueur.
Coyer et collaborateurs ont toutefois proposé que le genre Macrocystis est monospécifique (M. pyrifera) à la suite d'analyses génétiques montrant qu'il existe très peu de différences entre ces différentes espèces[2]. De plus, il a été démontré que les spécimens de ce genre peuvent présenter d'importantes différences morphologiques suivant les conditions environnementales[3].
Selon AlgaeBase (25 août 2017)[1] :
Selon ITIS (25 août 2017)[4] :
Selon NCBI (25 août 2017)[5] :
Selon World Register of Marine Species (25 août 2017)[6] :
Macrocystis est un genre d'algues brunes de la famille des Laminariaceae. Les thalles atteignent les 45 mètres de longueur.
Coyer et collaborateurs ont toutefois proposé que le genre Macrocystis est monospécifique (M. pyrifera) à la suite d'analyses génétiques montrant qu'il existe très peu de différences entre ces différentes espèces. De plus, il a été démontré que les spécimens de ce genre peuvent présenter d'importantes différences morphologiques suivant les conditions environnementales.
Le alghe del genere Macrocystis appartengono all'ordine Laminariales, classe Phaeophyceae. Sono comunemente conosciute come Kelp californiano.
Sono distribuite su quasi tutte le coste continentali dell'emisfero australe (Sudamerica, Africa meridionale, Australia, Nuova Zelanda) e lungo le coste del Pacifico orientale (Nordamerica). Sono in grado di sopravvivere in tutti i mari tranne che in quelli tropicali e artici.
Tra tutte le alghe sono quelle che possono raggiungere le maggiori dimensioni: la loro lunghezza può variare, a seconda del clima e di nutrimenti disponibili, dai 6 ai 60 metri e oltre.
In passato sono state usate per l'alimentazione umana e animale, come fertilizzante e per la fabbricazione di esplosivi.
Oggi vengono utilizzate prevalentemente a livello industriale: in Nord America, dove se ne raccolgono centinaia di tonnellate l'anno, sono la principale fonte di acido alginico, che trova una vasta applicazione nell'industria alimentare, farmaceutica, cosmetica, tessile, nell'industria delle colle e delle vernici e nell'industria metallurgica.
L'acido alginico arriva ad occupare nelle Macrocystis il 40% del peso secco della pianta, contro il 30% delle Laminariceae e il 20% delle Fucaceae.
Recentemente, anche i centri di thalassoterapia hanno adottato le grandi foglie di alghe Macrocystis per gli avvolgimenti del corpo e i bendaggi degli arti inferiori. La forte presenza di acido alginico di iodio, potassio e di oligoelementi, rende le foglie d'alga Macrocystis molto efficaci nei trattamenti di benessere per la spiccata azione detossinante e riattivante del metabolismo cellulare.
È inoltre utilizzata come concime fogliare.
Le alghe del genere Macrocystis appartengono all'ordine Laminariales, classe Phaeophyceae. Sono comunemente conosciute come Kelp californiano.
Macrocystis é um género monospecífico de algas castanhas do tipo kelp,[2] que contém a maior de todas as espécies de Phaeophyceae (Macrocystis pyrifera), cujos talos são capazes de atingir 45–60 m de comprimento. Estas macroalgas são em muitas regiões o principal componente das florestas submarinas de kelp, com distribuição alargada nas águas costeiras das regiões subtropical, temperada e sub-antárcticas do Hemisfério Sul (p. ex. as costas do Chile, Nova Zelândia, Austrália, ilhas Falkland e ilhas Auckland) e do Pacífico Nordeste (desde as costas da Baja California até Sitka, no Alaska). O epíteto específico resulta da presença de grandes flutuadores piriformes nos seus talos.
Os membros do género Macrocystis são algas marinhas gigantes, com grandes talos laminares, geralmente designados por lâminas, com comprimentos que em condições favoráveis podem ir até aos 45 a 60 m. As lâminas destas algas apresentam pneumatocistos na sua base, o que permite a formação de bosques submarinos de grandes esporófitos perenes, podem viver até 3 anos,[3] erectos por flutuação e formados por grandes frondes cujas lâminas sofrem um processo cíclico de senescência, podendo cada uma persistir por até 100 dias.[4]
Alguns indivíduos são tão grandes que os talos podem crescer até aos 60 m de comprimento,[5] com a maioria dos estipes a ultrapassar os 45 m de comprimento.[6][7]
Os estipes ligam-se ao substrato por um rizóide e ramificam-se três ou quatro vezes próximo da base, permanecendo sem ramificação até ao seu topo. As lâminas formam-se a intervalos irregulares ao longo do estipe,[6][8] cada lâmina com pelo menos um grande penumatocisto piriforme junto à base, permitindo manter o estipe erecto por flutuação.[9]
O género tem uma ampla distribuição natural nas regiões subtropical, temperada e sub-antártica do Hemisfério Sul, ocorrendo, por exemplo, nas costas da África do Sul, da Argentina, do Chile, do Peru, da Nova Zelândia, da Austrália, das ilhas Malvinas e das ilhas Auckland e ilhas do Oceano Austral até aos 60º de latitude sul, e no nordeste do Pacífico, desde a Península de Baja California (México) até Sitka, no Alaska, regiões onde Macrocystis é frequentemente um componente importante das florestas submarinas de kelp.[10]
O esporófito macroscópico é composto por múltiplas lâminas especializadas que crescem a partir da região que circunda o ponto de fixação ao substrato. Essas lâminas desenvolvem soros contendo esporângios que liberam esporos haplóides, que se transformam em gametófitos microscópicos femininos e masculinos. Os gametófitos, após encontrarem um substrato apropriado, crescem mitoticamente para eventualmente produzir gâmetas.[10]
Os gametófitos femininos libertam os seus ovos (oogónios) ao mesmo tempo que produzem e libertam uma feromona, o lamoxireno,[11][12] composto que desencadeia a libertação de esperma pelos gametófitos masculinos. O esperma de Macrocystis consiste em anterozóides biflagelados não-fotossintéticos, que se dirigem para os oogónios seguindo o gradiente de concentração de lamoxireno. O ovo é então fertilizado para formar um zigoto, que por mitoses sucessivas inicia o crescimento de um novo indivíduo.
As algas gigantes juvenis crescem directamente sobre o gametófito feminino, estendendo uma ou duas lâminas primárias e iniciando um rizóide rudimentar, que eventualmente cobrirá completamente o gametófito. O crescimento ocorre com o alongamento do estipe e a divisão das lâminas, processo que se desenvolve por meio de pequenas sulcos que se vão abrindo na zona onde a lâmina se insere no estipe, que se alargam até o dividir em dois. Os pneumatocistos desenvolvem-se após o surgimento dos primeiros rudimentos de lâmina.
As algas gigantes do género Macrocystis geralmente formam leitos extensos, com grandes e densa canópias flutuantes, ligadas por extensos rizoides, ou crampons, a substratos rochosos situados abaixo da linha da maré baixa.[6][10] A presença desses bosques submarinos cria condições ambientais específicas, albergando um um ecossistema com elevada biodiversidade, incluindo desde mamíferos a briozoários.
Para além de serem utilizadas em alimentação humana e animal, estas algas eram tradicionalmente recolhidas para fertilização dos campos e para produção de explosivos. Apenas na costa californiana dos Estados Unidos, eram recolhidas para esse fim cerca de 300 toneladas de lâminas por dia.[13]
No presente, a recolha continua intensa, especialmente para produção de algina (ou ácido algínico), produto com vasta utilização na indústria farmacêutica, na preparação de aditivos alimentares e nas indústrias têxtil e de refinação da celulose. Também é usado como fertilizante foliar em agricultura biológica. O ácido algínico corresponde a cerca de 40% do peso seco das frondes de Macrocystis, contra menos de 30% nas restantes Laminariaceae e 20% nas Fucaceae.
Entre os usos industriais modernos, para além das indústrias alimentar e farmacêutica, contam-se a produção de cosméticos, a produção têxtil e o fabrico de colas, vernizes e tintas e ainda a indústria metalúrgica.
Recentemente, os centros de talassoterapia também adoptaram o uso de grandes lâminas de Macrocystis para envoltórios corporais e ligaduras dos membros inferiores, na esperança que a forte presença de ácido algínico, de iodo, potássio e elementos vestigiais, sejam benéficos nos tratamentos para a desintoxicação e revitalização do metabolismo celular.
No presente entendimento do géneros, Macrocystis é um género monoespecífico tendo M. pyrifera como única espécie. Contudo, ao longo do tempo foram descritas pelo menos 17 espécies do género Macrocystis.[14] Solução semelhante já havia sido proposta em 1874 por Joseph Dalton Hooker, que com base na morfologia das lâminas tinha colocado todas as espécies então descritas no mesmo táxon sob o nome de Macrocystis pyrifera.[15]
Em tempos mais recentes, um grande número de espécies foram reclassificadas com base na morfologia do rizóide (ou crampon) e das lâminas, o que levou ao reconhecimento de três espécies distintas (M. angustifolia, M. integrifolia e M. pyrifera), conjunto a que foi adicionada uma quarta espécie (M. laevis) em 1986.[16]
Apesar disso, em 2009 e 2010, dois estudos de filogenia, recorrendo a características morfológicas[17] e moleculares,[18] demonstraram que Macrocystis é monospecífico (como M. pyrifera), o que é correntemente aceite pela comunidade ficológica.[19]
Apesar de considerado um género monospecífico, Macrocystis tem uma distribuição natural tão ampla[10] que alguns taxonomistas dividem M. pyrifera em quatro morfos, ou sub-espécies, da seguinte forma:
Macrocystis é um género monospecífico de algas castanhas do tipo kelp, que contém a maior de todas as espécies de Phaeophyceae (Macrocystis pyrifera), cujos talos são capazes de atingir 45–60 m de comprimento. Estas macroalgas são em muitas regiões o principal componente das florestas submarinas de kelp, com distribuição alargada nas águas costeiras das regiões subtropical, temperada e sub-antárcticas do Hemisfério Sul (p. ex. as costas do Chile, Nova Zelândia, Austrália, ilhas Falkland e ilhas Auckland) e do Pacífico Nordeste (desde as costas da Baja California até Sitka, no Alaska). O epíteto específico resulta da presença de grandes flutuadores piriformes nos seus talos.
Макроцистіс (Macrocystis ) — рід бурих водоростей родини Ламінарієві (Laminariaceae). Талом завдовжки до 60 м (вага до 150 кг), прикріплюється до грунту ризоїдами, з кількома гнучкими гілками, що мають листоподібні пластини з поодинокими повітряними бульбашками в основі, завдяки яким частина талому плаває на поверхні води. Відомо чотири види, що поширені в морях помірних поясів Південної і Північної півкуль. Утворюють великі зарості, що мають важливе значення в екології пов'язаних з ними організмів. Macrocystis pyrifera вирощують на морських фермах (в Каліфорнії) як харчовий продукт, на добриво і як енергетичну сировину (для отримання газу та інших видів пального). Макроцистіс використовують також для отримання солей альгінової кислоти.
Вчені до кінця не з'ясували, яким чином розмножується ця водорість, адже зростає макроцистіс на великій глибині, і як туди потрапляють молоді рослини - не цілком зрозуміло. Вважається, що спори макроцистіса проростають, тільки опинившись на мілководді. Молодняк кріпиться до невеликих камінців, які разом з відпливами і течіями потрапляють у відкрите море. Камінь, до якого прикріплений молодий макроцистіс, служить грузилом, за допомогою якого молодняк опускається на глибину 30-40 метрів. Опинившись у відповідних для розвитку умовах, макроцистіс вкорінюється і починає дуже швидко рости, додаючи по 10 см в день.
Це незавершена стаття з альгології.Макроцистіс (Macrocystis ) — рід бурих водоростей родини Ламінарієві (Laminariaceae). Талом завдовжки до 60 м (вага до 150 кг), прикріплюється до грунту ризоїдами, з кількома гнучкими гілками, що мають листоподібні пластини з поодинокими повітряними бульбашками в основі, завдяки яким частина талому плаває на поверхні води. Відомо чотири види, що поширені в морях помірних поясів Південної і Північної півкуль. Утворюють великі зарості, що мають важливе значення в екології пов'язаних з ними організмів. Macrocystis pyrifera вирощують на морських фермах (в Каліфорнії) як харчовий продукт, на добриво і як енергетичну сировину (для отримання газу та інших видів пального). Макроцистіс використовують також для отримання солей альгінової кислоти.
Макроцистис (лат. Macrocystis) — род бурых водорослей из семейства ламинариевых. Включает самые крупные из известных водорослей, превышающие длину 45 метров[2]. Отдельные экземпляры живут до 8—10 лет, хотя обычно жизнь водоросли короче. Используются в аквакультуре. Обитают в Южном полушарии. Растут на скалистых и каменистых грунтах на глубине 20—30 м.[3]
У представителей рода слоевище крепится к грунту ризоидами. Ствол имеет несколько длинных ветвей, на которых находится большое количество однолетних листовых пластин длиной 1 м и шириной 20 см с воздушными пузырями в основании. Само растение многолетнее, но его ветви с листовидными пластинами однолетние. Спорангии образуются на нижних пластинах-спорофиллах. Цикл жизни, чередование гетероморфных гаметофита и спорофита, сходен с жизненным циклом других бурых водорослей.[3] Насчёт длины макроцистиса существуют разные мнения. Если взять свежие источники, то в обзоре английского ботаника Г. Прескотта указывается: от 60 до 213 метров.
Макроцистис похож на гирлянду флажков неправильной формы или на хвост воздушного змея, унизанный лохмушками. Макроцистис намертво прикрепляется к грунту или скалам ризоидами, служащими водорослям чем-то вроде корней. В большой шторм кусок камня с макроцистисом может оторваться от скалы, но макроцистис никогда не оторвется от камня.
Макроцистис имеет форму стебля, сперва поднимающегося вверх, а затем у самой поверхности воды поворачивающегося и идущего горизонтально в направлении морского течения. Слоевище длиной до 45 м (масса до 150 кг) с ризоидами и листообразными пластинами, с воздушными пузырями, поддерживающими ветви и пластины у поверхности.х лучей, проникающих на большую глубину. Длинный тонкий ствол несёт на себе многочисленные пластинки. Верхушечная пластинка отделяет новые пластинки посредством косых разрывов с одной своей стороны. Основания пластинок грушевидно вздуты, содержат газовый пузырь. За счёт этого и длины ветвей верхняя часть таллома плавает у поверхности воды[4]. Рост таллома происходит за счёт вставочных меристем, располагающихся между стволиком и пластинками.
Таллом сложно организован, имеет кору, неокрашенные промежуточный слой и сердцевину. Сердцевина содержит крупные ситовидные трубки, обеспечивающие транспорт органических веществ[5]. Вещества перемещаются от активно фотосинтезирующих частей таллома к ризоидам и активно растущей верхушке, скорость их транспорта может достигать 78 см в час. Строение ситовидных трубок у макроцистиса иное, чем у цветковых растений; они лишены клеток-спутников, но имеют много митохондрий[6].
Из-за возможности подрыва естественных ресурсов водорослей учёные исследуют возможности выращивания макроцистиса, а именно макроцистиса грушевидного (Мacrocystis pyrifera) на плантациях. Так как эта водоросль быстро восстанавливается, возможно собирать до 3 урожаев в год. Опыты по её выращиванию уже провели в США, Франции и некоторых других государствах. В Калифорнии уже выращивают макроцистис грушевидный на морских фермах как пищевой продукт, на удобрение, как энергетическое сырьё (для получения газа и других видов горючего). Макроцистис также используется для получения солей альгиновой кислоты, которые применяются в целлюлозно-бумажной, парфюмерной, фармацевтической, консервной промышленности, а также в металлургии, электросварке и производстве строительных материалов, и других химических продуктов.
При выращивании макроцистиса рассаду укрепляют на сетке из искусственных волокон и погружают на глубину 12—24 м. Для обогащения поверхностных вод биогенами и улучшения роста водорослей требуется поднимать глубинные, обогащённые биогенами воды в верхние горизонты. На площади 1 га размещают около 1 тысячи растений, которые дают 300—500 тонн сырой массы в год. Собирают водоросли со специальных судов, срезающих и собирающих верхние части растений.[3]
Чарльз Дарвин, изучая эту водоросль у берегов Южной Америки, пришел к выводу, что её «леса» поддерживают существование гораздо большего числа видов, чем любое другое растение на Земле. Особенно важен макроцистис для морских ежей, моллюсков и рыб. Также леса из макроцистиса являются приютом для исчезающего вида — морских выдр. Каланы сооружают себе спальни из водорослей и охотятся на морских ежей, обитающих в их зарослях.
Макроцистис (лат. Macrocystis) — род бурых водорослей из семейства ламинариевых. Включает самые крупные из известных водорослей, превышающие длину 45 метров. Отдельные экземпляры живут до 8—10 лет, хотя обычно жизнь водоросли короче. Используются в аквакультуре. Обитают в Южном полушарии. Растут на скалистых и каменистых грунтах на глубине 20—30 м.
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