Kelp Forests

Under the cold ocean waves off California, giant plants called kelp grow taller than a three-story building, some reaching 100 feet from the sea floor to the surface! These towering underwater plants grow so thick together that fish, otters, and even sharks swim through them just like animals walk through a forest on land.

- What kelp is and how it grows so tall - Which animals live in a kelp forest - Why sea otters are the kelp forest's best friend - Why kelp forests matter for the whole ocean

Kelp is a giant type of seaweed, which is actually a kind of algae, not a plant with roots like a tree. Instead of roots, kelp holds onto rocks with a claw-like part called a holdfast. Giant kelp can grow up to 2 feet in a single day, making it one of the fastest-growing living things on Earth! It needs sunlight, cold water, and nutrients to grow that fast, so kelp forests are found in cool coastal waters like those off California, Chile, and South Africa.

A kelp forest is packed with life. Sea otters float on their backs among the kelp, wrapping themselves in it like a blanket so they don't drift away while they sleep! Garibaldi fish, which are bright orange, dart between the kelp stalks. Sea urchins crawl along the bottom and eat kelp, while leopard sharks and harbor seals hunt for food in the shadows of the swaying kelp blades.

Sea otters eat sea urchins, and that job is more important than it sounds. If there are too few otters, sea urchins multiply out of control and chew through kelp holdfasts, and the whole kelp forest can disappear, turning into a bare 'urchin barren.' By eating urchins, otters protect the kelp forest for every other animal that depends on it. Scientists call an animal like this a keystone species, because the whole habitat depends on it, the same way a keystone holds up a stone archway.