Nereocystis luetkeana
| Nereocystis luetkeana | ||||||||||||
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Nereocystis luetkeana in the aquarium |
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| Scientific name of the genus | ||||||||||||
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| Postels & Rupr. | ||||||||||||
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| Nereocystis luetkeana | ||||||||||||
| ( K. Mert. ) Postels & Rupr. |
Nereocystis luetkeana is the only species of the genus Nereocystis within the Laminariales . The up to 40 meters tall brown alga formsextensive kelp forests on the coasts of the Northeast and Northwest Pacific .
description
The thallus of Nereocystis luetkeana can grow up to 40 meters. The brown seaweed is anchored to the rocky subsoil with a hemispherical adhesive organ ( rhizoid ), the claw-like branched hooks of which arise in whorls around the base of the stem.
The very long, cylindrical, dark brown handle ( cauloid ) resembles a whip, which is why the alga is also called "bull-whip kelp" or "bull kelp" in America. The stem can reach up to 35 meters in length, depending on the water depth. Towards the top it becomes gradually thicker and ends in a hollow, club-like swelling (apophysis) two to seven centimeters in diameter. This carries, separated by a constriction, a spherical to egg-shaped, gas-filled pneumatocyst as a floating body with a diameter of 9 to 14 centimeters. Their fibrous wall is about two inches thick. The entire float can contain up to three liters of gas and keep the pneumatocyst on the surface of the water.
A tuft of 50 (up to 100) leaf-like organs arises at the apex of the pneumatocyst. These phylloids are golden brown, thin, broad band-shaped, up to four meters long and 15 centimeters wide and smooth-edged. They are attached to the pneumatocyst with forked ramifications. Their buoyancy keeps the phylloids at or near the surface of the water. In quiet locations, wide, wavy phylloids form, while in locations with strong waves, narrow band-shaped phylloids develop.
Development cycle
As with all laminariales , the visible tang is the sporophyte . It begins to grow in early spring and reaches its "canopy" on the surface of the water around midsummer. The alga grows very quickly, with an increase of 6 to 10 centimeters per day. The growth of the stalk is regulated by a phytochrome so that it stops as soon as red light components reach the alga near the surface. The photosynthesis rate of the leaf organs is highest in summer and early autumn . In winter, especially after storms, most of the phylloids die. No new seaweed can grow from the detention organ, so that Nereocystis is usually annual. Some specimens can only hibernate and experience a second year in sheltered places.
The two-flagellated haploid spores are formed in the fertile parts of the phylloids (Sori). The ripe Sori separate from the rest of the phylloid, float in the water and finally reach the bottom. One to four hours after separation, large amounts of spores are released, up to 23,000 per square centimeter and minute. They are viable for several days and can feed through photosynthesis. On the subsurface, they germinate into microscopic, male or female gametophytes , which consist of single-row, branched cell threads. After two to three months, the gametes , egg cells and sperm cells develop on them . After fertilization, the zygote settles and germinates into a young sporophyte.
The algae can spread over greater distances through the spores, through torn off parts of the seaweed or through the separated sori.
Occurrence
Nereocystis luetkeana occurs in the northeast Pacific from Alaska to central California . There it forms extensive kelp forests on rocky coasts in water depths of 10 to 20 meters. It was also found in the Northwest Pacific near the Commander Islands and Kamchatka .
ecology
Where the annual Nereocystis occurs together with the giant kelp ( Macrocystis pyrifera ), this perennial species displaces it to the most exposed places.
The sea urchins Strongylocentrotrus franciscanus and Strongylocentrotrus purpuratus feed on Nereocystis and thus have a strong influence on the population. The abalone sea snail Haliotis rufescens , other snails ( Tegula , Callistoma , Collisella pelta ) and various crustaceans also eat the alga.
More than 50 types of epiphytic algae colonize the stems and phylloids of Nereocystis , for example Porphyra nereocystis , ulva or antithamnion species, as well as epiphytic invertebrates such as bog animals ( Membranipora membranacea ), hydrozoans and barnacles . This causes direct shading, and if there is heavy growth, the weight can become so great that the phylloids sink into deeper, darker layers of water. A parasitic alga ( Streblonema ) causes deformations and the breaking off of the stem.
Several species of fish ( Synchirus gilli , Liparis sp., Phytichthys chirus ) live on the stems and leaf organs of Nereocystis . The stickleback-like Aulorhynchus flavidus lays its eggs on their pneumatocysts.
Systematics
The species was first described in 1829 by Karl Heinrich Mertens under the name Fucus luetkeanus . The first find comes from the Norfolk Sound near Sitka , Alaska. The species name honors the Russian naval officer Friedrich Benjamin von Lütke , who was lieutenant captain of the corvette Senjawin during the Russian North American expedition 1826-29 .
In 1840 Alexander Postels and Franz Josef Ruprecht put the species in a separate, monotypical genus Nereocystis (in: Illustrationes algarum ). The generic name means "bubble of the sea god" (from Greek Νηρεύς = Nereus and ancient Greek κύστις kýstis = "bubble") and refers to the spherical floating body that floats on the surface of the water. Other synonyms of Nereocystis luetkeana are Ulva priapus SGGmelin and Nereocystis priapus (SGGmelin) De A. Saunders. The genus Nereocystis is assigned to the Laminariaceae family .
use
Nereocystis is used economically to a small extent. In California and British Columbia it is harvested for the production of fertilizer and since the 1980s also as fodder for abalone cultures. Usually the upper parts are cut off, whereby the individual seaweed dies. The stocks of the annual species can be seriously damaged, especially if the harvest takes place before spore formation. In order to preserve the kelp forests , the harvest is now subject to certain restrictions ("kelp bed management").
The alga is edible, in Alaska its thick stalks are pickled and marketed as a specialty. The dried parts of the kelp are also used for arts and crafts. In Korea , Nereocystis is used in folk medicine .
swell
- ↑ a b c Michael D. Guiry in Michael D. Guiry, GM Guiry: Nereocystis luetkeana - In: Algaebase - World-wide electronic publication, National University of Ireland, Galway, accessed October 24, 2014
- ↑ a b c d e f 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. 206-207.
- ↑ a b c d e f g h i j Yuri Springer, Cynthia Hays, Mark Carr, Megan Mackey: Ecology and management of the bull kelp, Nereocystis luetkeana : A Synthesis with Recommendations for Future Research. Lenfest Ocean Program 2007 (pdf) .
