''Macrocystis pyrifera'', commonly known as giant kelp or giant bladder kelp, is a species of kelp (large brown algae), and one of four species in the genus ''Macrocystis''. Giant kelp is common along the coast of the eastern Pacific Ocean, from Baja California north to southeast Alaska, and is also found in the southern oceans near South America, South Africa, and Australia. Individual algae may grow to more than 45 metres long at a rate of as much as 2 feet per day. Giant kelp grows in dense stands known as kelp forests, which are home to many marine animals that depend on the algae for food or shelter. Humans harvest kelp for it is rich in iodine, potassium, and other minerals, but the primary product obtained from giant kelp is alginate.