Scientists Say: Kelp | Science News for Students

Scientists Say: Kelp

This large ocean organism looks like a plant but is actually a type of algae
Apr 23, 2018 — 6:30 am EST
Otter kelp

This otter is floating in a raft of kelp. All that can be seen at the surface are the tips of the kelp plants, which are anchored to the sea floor below.


Kelp (noun, “KEHLP”)

This is a group of large seaweeds. These seaweeds look a lot like plants, but they’re something else. Kelp are a type of brown algae — water-based organisms that get their energy from sunlight. Though they’re not plants, kelp have stemlike parts called stipes. They also have leaflike blades and rootlike holdfasts.

There are many different species of kelp. Some can grow up to 45 centimeters (18 inches) per day. And they can reach up to 53 meters (175 feet) in length. In some shallow parts of the ocean, such as the coasts of California, South America and Australia, kelp grow in huge forests. Those forests are important homes for sponges, fish, sea urchins, otters and other critters.

In a sentence

Some kelp forests are so large they can be spotted from space.

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Power Words

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algae     These are simple organisms that were once considered plants (they aren’t). As aquatic organisms, they grow in water. Like green plants, they depend on sunlight to make their food.

blade  (in biology) The flat, expanded part of a leaf of grass. In algae, a blade refers to the leaf-like part of kelp. (in machinery) The broad part of a machine that comes into contact with a material that is to be moved, such as the blade of a turbine coming into contact with air or water. A blade can also refer to the cutting part of an instrument such as a knife.

forest     An area of land covered mostly with trees and other woody plants.

holdfast  (in biology) A part that allows a plant to cling to a surface, such as a vine to a tree trunk. In algae, a holdfast is the root-like part of kelp that attaches to the seafloor.

kelp     A type of large seaweed that is usually a type of brown algae. They grow underwater and form large forests, providing habitat for many organisms. Some kelp forests are so large they can be seen from space.

organism     Any living thing, from elephants and plants to bacteria and other types of single-celled life.

sea     An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

seaweed     Large algae growing in the sea or on rocks below the high-water mark.

sponge     A primitive aquatic animal with a soft, porous body.

stipe  This is a stem-like part of kelp or the stem-like trunk of a mushroom. It is called a stipe instead of a stem because kelp and mushrooms are not plants, but algae and fungi.

urchin     Small, spine-covered sea animals without eyes or limbs which are related to sand dollars and starfish.