Kelp forest (Ethan Daniels / shutterstock.com)
Kelp is a marine brown algae of the order Laminariales. Growing in coastal waters of colder ocean regions kelp forests form a highly productive ecosystem. The genera Macrocystis and Nereocystis have a very high growth rate, adding up half a meter per day under optimal conditions. They can reach a total length of 80 meters (260 feet).