Bladderwrack

Fucus vesiculosus, commonly known as bladderwrack, is a brown alga in the family Fucaceae recognised by the paired, nearly spherical air bladders that usually line either side of its midrib, though younger plants may lack them. Its fronds grow up to one hundred fifty centimetres long and two and a half centimetres wide, branching in a forked pattern from a disc shaped holdfast, though unattached specimens also occur. It grows along the coasts of the North Sea, the western Baltic Sea and the Atlantic and Pacific Oceans, thriving on sheltered shores from the mid littoral to the lower intertidal zone and becoming stunted on more exposed shores. Bladderwrack was the original source of iodine, discovered in it in 1811, and was used extensively to treat goiter before modern iodine sources became available.