Kelps are the most complex and largest of all brown algae found in sea. Most kelps are found below the low tide level in temperate and subpolar latitudes.

These kelps grow in great abundance, providing food and shelter for many other organisms. Some kelps consists of a single large blade up to 10 ft in length. Their blades are harvested for food in several parts of the world. Kelp beds are harvested by chopping off the tops for the extraction of several natural products.