The cell walls of seaweeds contain long chain polysaccharides, which give flexibility to the algae and allow them to adapt to the variety of water movements in which they grow. For example, some brown seaweeds grow attached to rocks in very turbulent waters, requiring maximum flexibility to survive, and these contain a higher amount of these polysaccharides than brown seaweeds growing in calm waters.
Hydrocolloid polysaccharides have significant importance, both technologically and economically, since they are used in the food, pharmaceutical, medicinal, and biotechnological industries, due to their distinct physicochemical properties. Increase in demand for seaweeds in the manufacture of hydrocolloids, such as agar, alginate, and carrageenan, is anticipated to boost the adoption of seaweeds
Seaweeds have been used as a human food since ancient times, particularly in China, the Korean Peninsula and Japan. As people from these countries have migrated to other regions, they have taken this use of seaweed to their new countries so that dried and wet, salted seaweed products can now be found in most parts of the world. These seaweeds form the commercial side of the seaweed food industry. Seaweed has also been eaten by the coastal populations of many countries, sometimes as part of a subsistence living, sometimes as a regular ingredient of salad-type preparations, the latter especially in Hawaii and the warmer countries of Southeast Asia such as Indonesia, Malaysia, Philippines and Thailand.
Seaweeds have long been used as additives to soils, mainly in coastal areas where the wet or partly dried seaweed is easily transported to the area to be fertilized. The high fibre content of the seaweed acts as a soil conditioner and the mineral content as a fertilizer.