Fucus vesiculosus, known by the common name
bladder wrack or
bladderwrack, is a
seaweed found on the coasts of the
North Sea, the western
Baltic Sea, and the
Atlantic and
Pacific Oceans, also known by the common names
black tang,
rockweed,
bladder fucus,
sea oak,
black tany,
cut weed,
dyers fucus,
red fucus, and
rock wrack. 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.