Fucus vesiculosus

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 and Pacific Oceans. 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. 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. 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 to lower intertidal levels. It is rare on exposed shores, where any specimens may be short, stunted and without the air vesicles. 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. Phlorotannins in Fucus vesiculosus act as chemical defenses against the marine herbivorous snail Littorina littorea., while galactolipids act as herbivore deterrents against the sea urchin Arbacia punctulata. Methyl jasmonate may induce the phlorotannins production. Fucophlorethol A is a type of phlorotannin found in F. vesiculosus.