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What is Macrocystis?

IVSAT 2024

Macrocystis is a kelp genus with only one species (large brown algae). The Phaeophyceae, or brown algae genus Macrocystis includes the largest members of the family. Sporophytes are perennial and can live for up to three years; however, stipes/fronds within a single organism go through senescence, with each frond lasting about 100 days. The genus is widespread in the Southern Hemisphere's subtropical, temperate, and sub-Antarctic oceans (e.g., Chile, New Zealand, Australia, Falkland Islands, Auckland Islands, and others), as well as the northeast Pacific from Baja California to Sitka, Alaska. Macrocystis is a common species in temperate kelp forests.

Description Macrocystis

Macrocystis is a single-species genus with only one species, Macrocystis pyrifera. Some individuals are so large that their thallus can reach 60 meters in length (200 ft). The stipes branch three or four times near the base after emerging from a holdfast. The stipe develops blades at irregular intervals. M. pyrifera can reach a length of over 45 meters (150 feet). Each blade has a gas bladder at its base, and the stipes are unbranched.

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Life Cycle of Macroscopic Sporophyte

Many specialized blades develop near the holdfast on the macroscopic sporophyte. These blades are covered in sporangia, which release haploid spores that grow into microscopic female and male gametophytes. After reaching the required substrate, these gametophytes evolve mitotically to produce gametes.

Females release a pheromone called tamoxifen along with their eggs (oogonia). This substance causes males to release sperm. The Macrocystis sperm is made up of non-synthetic biflagellate antherozoids that accompany the lamoxirene to the oogonia. The egg is then fertilized, resulting in the zygote, which starts to develop via mitosis.


Juvenile giant kelp grows directly on the parent female gametophyte, spreading one or two primary blades and forming a rudimentary holdfast that will gradually fully cover the gametophyte. The lengthening of the stipe and the splitting of the blades are signs of development. This is accomplished by tiny tears where the blade hits the stipe, causing the stipe to break in half. After the first few blades split, pneumatocysts form.

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On rocky substrata between the low intertidal, Macrocystis forms extensive beds, massive "floating canopies." It was harvested by barges along the California coast, which used massive blades to harvest up to 300 tonnes per day.

Species of Macrocystis 

Within the genus Macrocystis, 17 species were initially described. Following blade morphology, Hooker classified them all as Macrocystis pyrifera in 1874. The vast number of species were reclassified in modern times based on holdfast morphology, which separated three species (M. angustifolia, M. integrifolia, and M. pyrifera), and blade morphology, which added a fourth species (M. angustifolia, M. integrifolia, and M. pyrifera) In 1986, (M. laevis) in 1986. However, two studies published in 2009 and 2010 using both morphological and molecular methods demonstrated that Macrocystis is monospecific (as M. pyrifera), which is now recognized by the phycological community.

Distribution: Macrocystis can be found along the eastern Pacific coast from Alaska to Mexico, as well as in Australia, New Zealand, South Africa, and most sub-Antarctic islands up to 60 degrees South.

Macrocystis Pyriformis

Macrocystis pyrifera, also known as giant kelp or giant bladder kelp, is a kelp (large brown algae) that belongs to the genus Macrocystis. It is one of four species in the genus Macrocystis. It is a heterokont, not a herb, despite its appearance. Giant kelp can be found along the western Pacific Ocean coast from Baja California to southeast Alaska, as well as in the southern oceans South America, South Africa, Australia, and New Zealand are all close by. Individual algae can reach lengths of more than 45 meters (150 feet) and grow at a rate of up to 60 centimetres (2 feet) per day. Kelp forests, which are thick stands of giant kelp, are home to many marine species that rely on the algae for food or shelter. Alginate is the most common commercial product made from giant kelp, but it is also harvested for human use on a limited basis because it is high in iodine, potassium, and other minerals. It can be used in cooking in many of the same ways as other sea vegetables, and it's especially good in bean dishes.

Features and Occurrence

M. pyrifera is the most massive of all the algae. The most common stage of the life cycle is the sporophyte, which is perennial and has individuals that live for several years. Individuals can grow up to 50 meters (160 feet) in length. Since the kelp grows in a diagonal direction due to the ocean current pressing towards it, it also grows much longer than the distance from the bottom to the top. Blades form at irregular intervals along the stipe, each with a single pneumatocyst (gas bladder) at its base. Sporophylls are a cluster of blades at the base of each stalk that lack pneumatocysts and instead form small sacks on the blade that release biflagellate zoospores.

M. integrifolia, a related and similar-looking but smaller species, grows to just 6 m (20 ft) in length. It can be found on intertidal or shallow subtidal rocks along the Pacific coasts of North and South America (from British Columbia to California). M. pyrifera can be found in the subtidal zone of the southern North Island, the South Island, Chatham, Stewart, Bounty, and Antipodes as well as the Campbell Islands in New Zealand. On rocky outcroppings and sheltered open coasts, the species can be found.

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FAQs on Macrocystis

1. What Do Macrocystis Pyrifera Eat?

Ans. Brown algae, like all plants and seaweeds, need both chlorophyll and sunlight for photosynthesis and development. This amazing kelp could be the world's fastest-growing organism, with growth rates of up to 50 cm per day in ideal conditions. The giant kelp does not have roots because it is not a weed. Instead, it gets all of its nutrients from the sea, and it's bound to the rocky bottom by a device called a holdfast.

2. What is Macrocystis Pyrifera Used For?

Ans. M. pyrifera has been used as a food source for several years; it also includes several compounds such as iodine, potassium, other minerals, vitamins, and carbohydrates, making it a dietary aid. California kelp beds were harvested as a source of soda ash in the early twentieth century.

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