How many species of kelp are there?
Kelp
Kelp grows in "underwater forests" (kelp forests) in shallow oceans, and is thought to have appeared in the Miocene, 23 to 5 million years ago.[4] The organisms require nutrient-rich water with temperatures between 6 and 14°C (43 and 57°F). They are known for their high growth rate—the genera Macrocystis and Nereocystis can grow as fast as half a metre a day, ultimately reaching 30 to 80 metres (100 to 260ft).[5]