Giant kelp is not a plant, it does not have roots. Instead, it obtains all of the necessary nutrients directly from the water and is attached to the rocky bottom by a structure known as a holdfast. Like plants, however, the giant kelp harvests the sun’s energy through photosynthesis and does not feed on other organisms. This species is one of the fastest-growing species in the world, and under perfect conditions, it has been known to grow up to two feet (60 cm) in a single day. Once individual giant kelp reaches the sea surface, it continues to grow horizontally, floating in large mats that shade the water column and seafloor below. In order to remain upright, each giant kelp blade (leaf) includes a gas-filled pod that floats.