Giant kelp Facts for Kids

Quick facts for kids Giant kelp

Scientific classification
Order:	Laminariales
Family:	Laminariaceae
Species:	M. pyrifera
Binomial name
*Macrocystis pyrifera*

Macrocystis pyrifera, often called giant kelp or giant bladder kelp, is a type of kelp. Kelp are very large brown algae that live in the ocean. This specific kind of giant kelp is one of four species in the Macrocystis group.

You can find giant kelp along the eastern Pacific Ocean coast, from Baja California up to southeast Alaska. It also grows in the southern parts of the ocean near South America, South Africa, Australia, and New Zealand. These amazing algae can grow to be over 60 meters (about 200 feet) long! They can even grow as much as 60 centimeters (about 2 feet) in a single day.

Giant kelp often grows in thick groups called kelp forests. These forests are like underwater cities, providing food and shelter for many different marine animals. People also use giant kelp. It's a source of alginate, which is used in many products. Plus, some people eat giant kelp because it's full of good things like iodine and potassium. It can add a special flavor to dishes, especially bean meals.

What is Giant Kelp?
How Does Giant Kelp Grow?
Where Does Giant Kelp Live?
How Do People Use Giant Kelp?
Protecting Giant Kelp Forests
Images for kids
See also

What is Giant Kelp?

Giant kelp is the biggest type of algae in the world. The part of the kelp you usually see is called the sporophyte. This part lives for many years. A single giant kelp plant can grow to be 60 meters (200 feet) long or even more! Sometimes, it grows even longer than the water is deep because ocean currents push it to grow diagonally.

The kelp plants grow from a strong base called a holdfast, which acts like roots, anchoring the plant to rocks on the ocean floor. From this holdfast, several stalks grow and branch out. Along these stalks, you'll find many blades (which look like leaves). At the bottom of each blade is a special gas-filled bubble called a pneumatocyst. These bubbles help the blades float towards the surface, so they can get sunlight.

A similar but smaller type of kelp, M. integrifolia, only grows to about 6 meters (20 feet) long. It's found on rocks in shallow waters along the Pacific coast of North America (from British Columbia to California) and South America. In New Zealand, giant kelp lives in the deeper parts of the ocean around many islands.

How Does Giant Kelp Grow?

Juvenile Macrocystis pyrifera at Point Lobos State Reserve

Giant kelp is one of the fastest-growing living things on Earth! It can grow about 60 centimeters (2 feet) every day. This means it can reach over 45 meters (150 feet) in length in just one growing season.

Young giant kelp plants start growing right on their parent plant, which is called a gametophyte. To get started, a young kelp grows one or two main blades and a small holdfast. This holdfast helps it stick to the rocky bottom. As the kelp gets bigger, more blades grow from its tip. The holdfast also gets larger and can even cover the entire rock it's attached to.

The kelp grows by its central stalk, called a stipe, getting longer. New blades form by the existing blades splitting. At the very tip of the growing stalk, there's a single blade. Small gas bladders start to grow along one side of this blade. As these bladders and the stalk grow, tiny tears appear in the attached blade. Once these tears are complete, each bladder supports its own separate blade along the stalk. The bladders and their blades are attached at different spots along the stalk.

Where Does Giant Kelp Live?

Giant kelp is found in many places around the world, including North America (Alaska to California), South America, South Africa, New Zealand, and southern Australia. It likes cooler ocean water, where the temperature stays below 21 degrees Celsius (70 degrees Fahrenheit). You can also find it near Tristan da Cunha in the middle of the South Atlantic Ocean.

When the ocean floor is rocky, giant kelp can anchor itself and form huge "floating canopies" on the surface. When there are many giant kelp plants together, they create amazing kelp forests. These forests are vital homes for countless marine animals. Many species rely on the kelp directly for food and shelter, while others use the kelp forest as a place to hunt for prey. The large size of the kelp and the huge number of plants in these forests change how much light gets through, how ocean currents flow, and even the water chemistry in the area.

In very crowded kelp forests, individual giant kelp plants sometimes compete with each other for space and resources like sunlight.

How Do People Use Giant Kelp?

For many years, people have used giant kelp as a food source. It's also packed with good things like iodine, potassium, other minerals, vitamins, and carbohydrates, so it's been used as a healthy supplement. In the early 1900s, kelp beds in California were harvested to get soda ash.

Interest in giant kelp grew a lot in the 1970s and 1980s. This was mainly because of the demand for alginate, which is used in many products like thickeners in food and cosmetics. People also looked into growing kelp for animal feed during an energy crisis. However, growing giant kelp on a very large scale never really took off. When the energy crisis ended and alginate prices dropped, research into farming Macrocystis slowed down.

Today, the demand for giant kelp is growing again. People are finding new ways to use it, such as in fertilizers, for cleaning up pollution (bioremediation), and as food for animals like abalone and sea urchins that are raised in farms. Scientists are even researching if giant kelp could be used to feed other farmed seafood, like shrimp. Recently, giant kelp has also been studied as a possible source for making ethanol, which can be used as biofuel.

Protecting Giant Kelp Forests

In recent years, kelp forests have shrunk a lot in places like Japan, Chile, Korea, Australia, and North America. While harvesting kelp for food and other uses might not be the biggest problem, there are other serious threats.

One natural event that harms giant kelp is El Niño. During El Niño cycles, warm, tropical water from the South Pacific moves into northern waters. Since giant kelp needs cold water to survive, this warm water can kill off large areas of kelp. In California, El Niño also caused a huge increase in the number of Purple Sea Urchins. These sea urchins love to eat giant kelp. By the late 2000s, much of the giant kelp along the California coast had almost disappeared.

Scientists and people who work to protect nature are always looking for ways to bring the kelp forests back to their healthy state. Some methods include building artificial reefs for kelp to grow on, reducing the number of Purple Sea Urchins in areas where there are too many, and planting new kelp roots on the ocean floor.