Giant kelp
| Giant kelp | ||||||||||||
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Giant kelp ( Macrocystis pyrifera ) |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Macrocystis | ||||||||||||
| C. Agardh | ||||||||||||
| Scientific name of the species | ||||||||||||
| Macrocystis pyrifera | ||||||||||||
| ( Linnaeus ) C. Agardh |
The giant kelp ( Macrocystis pyrifera ) is the only species of the brown algae genus Macrocystis in the order of the Laminariales . With a length of up to 45 meters, it is the largest of all brown algae and also the largest fixed ( benthic ) sea creature. The giant kelp is widespread on the Pacific coast of North America as well as on the sea coasts of the southern hemisphere . There it forms productive kelp forests . The giant kelp is of economic importance for the production of alginates .
description
The sporophyte of the giant seaweed is a large, light to dark brown seaweed that can be up to 45 meters long. Its thallus is divided into adhesive organ ( rhizoid ), stem and leaf-like phylloids . The extensively branched, root-like rhizoid anchors it to the rocky subsoil. The upright, very long stem is forked two to four times near the base and carries the phylloids on one side at regular intervals. These have a gas-filled bladder (pneumatocyst) on the "petiole", which keeps the seaweed upright in the water. The more or less pear-shaped swim bladders gave the species name pyrifera (= pear-bearing). The phylloids are undivided, up to 80 cm long, broadly lanceolate to narrowly tongue-shaped, with a crinkled, wrinkled or blistered surface and a serrated edge. New leaf organs are formed by splitting longitudinally at the tip of the thallus. The seaweed can grow eight to ten inches per day.
Leaf-like sporophylls are formed on shorter stems at the base , which carry sporangia arranged in groups ( sori ) . Each sporangium releases 32 haploid two-flagellated spores into the water, which are displaced with the current. They settle on a suitable surface and germinate into microscopic, male or female gametophytes . These form egg cells or sperm. With the help of the pheromone lamoxirene, the sperm find their way to the egg cells. A large seaweed (sporophyte) grows again from the fertilized egg cell.
Occurrence and ecology
The giant kelp occurs in cold to warm seas. The distribution area includes the Pacific coast of North America from Alaska to California , South America , Atlantic Islands ( Gough Island , Tristan da Cunha , Canaries ), South Africa , the Indian Ocean , Australia and New Zealand , the Antarctic and sub-Antarctic islands .
It grows near the coast below the low water line , mostly in 6–20 meters water depth, in very clear water rarely up to 80 meters water depth. The giant kelp can also occur in the intertidal zone , where the populations mostly only show vegetative reproduction.
The giant kelp is an essential element of many kelp forests , which are extremely productive habitats for numerous marine creatures. In the giant kelp forests off the coast of California, the sporophytes are long-lived and form extensive "canopy" below the surface of the water, shading the subsurface. They also reproduce abundantly here. Worldwide, however, most of the giant kelp populations tend to be changing, narrower kelp forest fringes, the offspring of which often come from a greater distance.
At higher latitudes , the growth of the sporophytes proceeds in a seasonal rhythm and is dependent on solar radiation. At low latitudes, however, it is mainly determined by the availability of nutrients.
Systematics
It was first described in 1771 by Carl von Linné under the name Fucus pyrifer . Carl Adolph Agardh placed the species in the genus Macrocystis in 1820 . The giant kelp was previously assigned to the Lessoniaceae family , but according to molecular genetic studies it belongs to the Laminariaceae family .
The taxonomy of the genus Macrocystis has long been controversial. Over 17 species have been described, which should differ in the appearance of leaf and adhesive organs. Four types of it have long been recognized. After morphological and molecular genetic studies it turned out in 2010 that the worldwide occurrence is a single species, so the genus Macrocystis is monotypical .
Synonyms are Fucus giganteus Gaudichaud, Fucus pyrifer L., Laminaria pyrifera (L.) JV Lamouroux, Macrocystis angustifolia Bory de Saint-Vincent, Macrocystis communis Bory de Saint-Vincent, Macrocystis pyrifera var. Humboldtii Bonpland, Macrocystis humboldtii (Bonardhand.) C.Agardhand , Macrocystis integrifolia Bory de Saint-Vincent, Macrocystis laevis Chhay., Macrocystis latifolia Bory de Saint-Vincent, Macrocystis pyrifera var. longibullata Reinsch, Macrocystis pyrifera var. luxurians JDHooker & Harvey, Macrocystis luxurians (JDHooker & Harvey) J.Agardh, Macrocystis orbigniana Montagne, Macrocystis pelagica Areschoug, Macrocystis planicaulis C. Agardh and Macrocystis tenuifolia Postels & Ruprecht.
use
The giant kelp is used in many countries to obtain alginates , which are used in the food industry, among other things. For this purpose, the seaweed stocks are harvested with trawlers . The annual yield reached 150,000 t fresh weight off the coast of California. The giant kelp is also used as food for sea snail ( abalone ) cultures.
swell
- ↑ a b c d e f g Michael H. Graham, Julio A. Vásquez, Alejandro H. Buschmann: Global ecology of the giant kelp Macrocystis. From ecotypes to ecosystems. - In: Oceanography and Marine Biology: An Annual Review , Volume 45, pp. 39–88, 2007. pdf ( Memento of the original dated August 3, 2014 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b c d e Wolfram Braune: Marine algae. A color guide to the common benthic green, brown and red algae of the world's oceans . Ruggell: Gantner, 2008, ISBN 978-3-906166-69-8 , pp. 202-205.
- ↑ a b c d e Michael D. Guiry, GM Guiry: Macrocystis pyrifera - In: Algaebase - World-wide electronic publication, National University of Ireland, Galway, accessed June 2, 2014
- ↑ EC Macaya, GC Zuccarello: DNA barcoding and genetic divergence in the giant kelp Macrocystis (Laminariales) . In: Journal of Phycology , Vol. 46 (4), pp. 736-742, 2010. Abstract
