Fucus vesiculosus

File:Fucus vesiculosus closeup.jpg

Bladder wrack is named for its conspicuous air vesicles

Fucus vesiculosus, known by the common names bladderwrack, black tang, rockweed, sea grapes, bladder fucus, sea oak, cut weed, dyers fucus, red fucus and rock wrack, is a brown alga a seaweed found on the coasts of the North Sea, the western Baltic Sea and the Atlantic and Pacific Oceans. It was the original source of iodine, discovered in 1811, and was used extensively to treat goitre.

Description

The fronds of F. vesiculosus grow to Template:Convert long and Template:Convert wide and have a prominent midrib throughout. It is typically attached by a basal disc-shaped holdfast but can also be unattached.<ref>Template:Cite journal</ref> It has almost spherical air bladders, which are usually paired one on either side of the mid-rib but may be absent in young plants. The margin is smooth and the frond is dichotomously branched. It is sometimes confused with Fucus spiralis with which it hybridises and is similar to Fucus serratus.<ref name=MarLIN>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Newton, L. 1931. A Handbook of British Seaweeds. London. British Museum (Natural History)</ref>

Biology

Plants of F. vesiculosus are dioecious. Gametes are generally released into the seawater under calm conditions, and the eggs are fertilized externally to produce a zygote.<ref name="MarLIN" /> Eggs are fertilized shortly after being released from the receptacle. A study on the coast of Maine showed that there was 100% fertilization at both exposed and sheltered sites.<ref name="MarLIN" /> Continuously submerged populations in the Baltic Sea are very responsive to turbulent conditions. High fertilization success is achieved because the gametes are released only when water velocities are low.<ref>Template:Cite journal</ref>

Individuals of F. vesiculosus from the North Sea colonized the Baltic Sea less than 8,000 years ago. The event is paralleled by a switch from what seems to be obligate sexual recruitment to facultative asexual recruitment.<ref name=":0">Template:Cite journal</ref> Asexual reproduction in Baltic Sea populations is accomplished by the production of adventitious branches that come loose and reattach to the bottom by the formation of rhizoids. Asexual reproduction is also important for maintaining unattached populations.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref> Adventitious branches are present in thalli of F. vesiculosus in other areas too but asexual formation of new thalli has never been reported outside the Baltic Sea.<ref name=":0" /><ref name=":1">Template:Cite journal</ref>

Distribution

Fucus vesiculosus is a common large brown alga on the shores of the British Isles.<ref name=book>Template:Cite book</ref> It has been recorded from the Atlantic shores of Europe, Northern Russia, the Baltic Sea, Greenland, Azores, Canary Islands, Morocco and Madeira.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Nygård 08">Template:Cite journal</ref> It is also found on the Atlantic coast of North America from Ellesmere Island, Hudson Bay to North Carolina.<ref name="Taylor 57"/>

Ecology

The species is especially common on sheltered shores from the middle littoral to lower intertidal levels.<ref name="Taylor 57">Template:Cite book</ref> It is rare on exposed shores, where any specimens may be short, stunted and without the air vesicles.<ref>Template:Cite book</ref> F. vesiculosus supports few colonial organisms but provides a canopy and shelter for the tube worm Spirorbis spirorbis, herbivorous isopods such as Idotea and surface-grazing snails such as Littorina obtusata.<ref name=MarLIN/> Phlorotannins in Fucus vesiculosus act as chemical defenses against the marine herbivorous snail Littorina littorea,<ref>Template:Cite journal</ref> while galactolipids act as herbivore deterrents against the sea urchin Arbacia punctulata.<ref>Template:Cite journal</ref> Methyl jasmonate may induce the phlorotannins production.<ref>Template:Cite journal</ref> Fucophlorethol A is a type of phlorotannin found in F. vesiculosus.<ref>Template:Cite journal</ref>

Uses

Fucus vesiculosus can be cooked and eaten.<ref name="tfb">Template:Cite book</ref>

It was the original source of iodine, discovered in 1811, and was used extensively to treat goitre, a swelling of the thyroid gland related to iodine deficiency.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

It is also sold as a nutritional supplement. Primary chemical constituents include mucilage, algin, mannitol, fucitol, beta-carotene, zeaxanthin, volatile oils, iodine, bromine, potassium and other minerals.Template:Citation needed

Adverse effects

Consumption of F. vesiculosus can cause platelet inhibition, which may potentiate the anticoagulant activity of warfarin (Coumadin).<ref name=ute>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It should be avoided before surgery.<ref name="ute" />

Some people may suffer an allergic reaction to the iodine in F. vesiculosus.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

See also

• Edible seaweed
• Iodine § Allergic reactions

External links

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