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 seaweed found on the coasts of the North Sea, the western Baltic Sea and the Atlantic Ocean and . 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 long and wide and have a prominent midrib throughout. It is attached by a basal disc-shaped holdfast. 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.
[Newton, L. 1931. A Handbook of British Seaweeds. London. British Museum (Natural History)]
Biology
Plants of
F. vesiculosus are
dioecious.
are generally released into the seawater under calm conditions, and the eggs are fertilized externally to produce a zygote.
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.
Continuously submerged populations in the
Baltic Sea are very responsive to turbulent conditions. High
fertilisation success is achieved because the
are released only when water velocities are low.
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.
Distribution
Fucus vesiculosus is a common large alga on the shores of the
British Isles.
It has been recorded from the Atlantic shores of
Europe, Northern Russia, the
Baltic Sea,
Greenland,
Azores,
Canary Islands, Morocco and
Madeira.
It is also found on the Atlantic coast of
North America from
Ellesmere Island,
Hudson Bay to
North Carolina.
Ecology
The species is especially common on sheltered shores from the middle
Littoral zone to lower
intertidal zone.
It is rare on exposed shores, where any specimens may be short, stunted and without the air vesicles.
supports few colonial organisms but provides a canopy and shelter for the tube worm
Spirorbis spirorbis, herbivorous
such as
Idotea and surface-grazing
gastropod such as
Littorina obtusata.
[ in Fucus vesiculosus act as chemical defenses against the marine herbivorous snail Littorina littorea,]
Uses
Fucus vesiculosus can be cooked and eaten.
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.
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 .
Adverse effects
Consumption of F. vesiculosus can cause platelet inhibition, which may potentiate the anticoagulant activity of warfarin (Coumadin).
Some people may suffer an allergic reaction to the iodine in F. vesiculosus.
See also
External links
