What chemical element was first extracted from kelp?
This element was discovered by the French chemist Bernard Courtois in 1811. He extracted the element from kelp ash which was used in the production of saltpeter.
Two years later scientists from other countries started studies of this substance and proved that this was really a new element. A bit later it was called iodine - from the Greek word "iodes/ioeides" that means "dark blue, violet".
By the way, seaweed such as Laminaria is capable of iodine producing in much greater amount than any other living organism.