Algal photosynthesis oxygenates all waters. Algae are the primary producers, the base of the food pyramid, of the food chains of aquatic habitats. The products of marine algae or seaweeds turn up in a huge range of everyday goods. From the late 17th century, brown seaweeds were burned for their mineral-rich ash, which yielded soda for making soap and glass, and potash for fertilizer. Chemical elements bromine and iodine were first isolated from this ash and iodine is still extracted from seaweed in Japan.
Seaweeds continue in wide use as fertilizers.
Brown Algae are the basis of the alginates industry. Alginic acid, first isolated in 1883, is a mucilaginous polymer with a structure similar to that of cellulose. Its salts, alginates, absorb many times their own weight of water, have a wide range of viscosity and readily form gels, and are non-toxic. They have countless uses in the manufacture of pharmaceuticals, cosmetic creams, paper and cardboard, and processed foods. They are moulded into sausage skins, give structure to ice cream and ketchup, and maintain the frothy head on beer.