Laminaria hyperborea
From Wikipedia, the free encyclopedia
| Laminaria hyperborea | |
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Scientific classification  | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Stramenopiles |
| Phylum: | Ochrophyta |
| Class: | Phaeophyceae |
| Order: | Laminariales |
| Family: | Laminariaceae |
| Genus: | Laminaria |
| Species: | L. hyperborea |
| Binomial name | |
| Laminaria hyperborea | |
| Synonyms | |
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Laminaria hyperborea is a species of large brown alga, a kelp in the family Laminariaceae, also known by the common names of tangle and cuvie. It is found in the sublittoral zone of the northern Atlantic Ocean. A variety, Laminaria hyperborea f. cucullata (P.Svensden & J.M.Kain, 1971) is known from more wave sheltered areas in Scandinavia.[2]
Laminaria hyperborea is a massive, leathery seaweed, up to 360 cm long.[3] The holdfast is large and cone-shaped, with branched rhizoids, looking rather like a bird's foot. The stipe is circular in cross section, rough, thick at the base and tapering upwards. Older stipes are often covered with epiphytic red algae. The laminate blade is deeply divided into linear segments and is yellowish brown with large digitate segments.[4][3] It is a long-lived species and has been recorded as surviving for 15 years.[5]
Laminaria hyperborea can be distinguished from the rather similar L. digitata by being paler in colour and having a longer stipe which snaps when it is bent sharply.[4] Laminaria ochroleuca is also similar but is more yellow in colour and does not have the rough stipe found in L. hyperborea.
Distribution and habitat
The range is the northeast Atlantic Ocean (including the Baltic and North Seas), from the North Cape, Norway and the Kola Peninsula south to central Portugal.[6][7]
Laminaria hyperborea grows on rocks in the sublittoral zone at depths down to about 10 m (35 ft) in turbid waters and down to 30 m (100 ft) where the water is clear.[8] It tends to be the dominant species in a narrow zone near low-water at spring tides. It also predominates in deeper waters on stable substrates in eave exposed areas[9] while Saccharina latissima tends to be dominant in sheltered areas[10] or those with less stable substrates.[11] Down to about 15 m (50 ft) the growth may be very dense and may be referred to as a "kelp forest" but at greater depths there is a more open community and these areas have been referred to as "parks".[12]
Biology
In young individuals of L. hyperborea, the annual growth consists mainly of the enlargement of the blade. This maximises the photosynthetic opportunity while the plant's low stature causes it to be overshadowed. In later years, more growth takes place in the stipe and holdfast. A new frond grows annually in the spring from the top of the stipe. The old frond is sloughed off later after much of its nutrient content has been transferred to the new growth.[8]
Laminaria hyperborea can liberate upward of a million zoospores from sori on the surface of the blade during the course of a few weeks during the winter. These have flagella and settle after about 24 hours before developing into microscopic gametophytes which become fertile in about 10 days. Male gametophytes release large quantities of motile sperm, apparently stimulated to do so by the release of female gametes by the female gametophytes in the vicinity. The fertilised zygotes germinate into young sporophytes which will grow into the mature seaweed.[8] Sexual reproduction is dependent on a minimum quantity of blue light; under less than optimal conditions, the gametophytes may develop vegetatively instead.[8]
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