Background Info

Strange forests lurk beneath the waves of sunny California. These underwater forests have no trees, however. Their canopy is provided by enormous seaweed: kelp.

Kelp forests are dominated by two species of the seaweed: giant kelp and bull kelp. Giant kelp and bull kelp share many features: holdfasts, stipes, pneumatocysts, and blades.

Read the information in the photo gallery to learn more about these unusual features, and answer the following questions.

Questions

1. 

What is a stipe?

Show Answer

A stipe is the kelp's thick, hollow stalk or stem.

2. 

What is a pneumatocyst?

Show Answer

A pneumatocyst is an air-filled sac that keeps the kelp buoyant.

3. 

What is a blade?

Show Answer

A blade is the thick, ridged, leaf-like structure where a kelp absorbs sunlight and oxygen for photosynthesis.

4. 

What is a holdfast?

Show Answer

A holdfast is the strong, root-like structure that attaches the kelp to the rocky substrate.

5. 

What is a thallus?

Show Answer

A thallus is the body of a plant-like organism that is not differentiated into roots, stems, or leaves. Algae, fungi, and lichen are composed of thalli.

6. 

What are the differences between giant kelp and bull kelp?

Show Answer

They have different arrangements of pneumatocysts and blades.

Bull kelp has a single pneumatocyst on its stipe. The pneumatocyst holds many blades.

Giant kelp has many pneumatocysts on its stipe. Each pneumatocyst holds a single blade.

7. 

What species of kelp is more likely to wash up on the beaches of Vancouver Island, British Columbia, Canada? On the beaches of San Diego, California?

Show Answer

Bull kelp is more common around Vancouver, while giant kelp is more common around San Diego.

For Further Exploration

Vocabulary

Term Part of Speech Definition Encyclopedic Entry

blade

Noun

large, flat, leaf-like structure on some seaweeds.

buoyant

Adjective

capable of floating.

canopy

noun, verb

the top layer of a forest formed by the thick leaves of very tall trees.

corrugated

Adjective

bent into rigid folds.

current

Noun

steady, predictable flow of fluid within a larger body of that fluid.

Encyclopedic Entry: current

El Nino

Noun

irregular, recurring weather system that features a warm, eastern-flowing ocean current in the eastern Pacific Ocean.

Encyclopedic Entry: El Niño

holdfast

Noun

root-like structure that attaches the kelp thallus (body) to the rocky substrate.

indigenous

Adjective

native to or characteristic of a specific place.

kelp

Noun

type of seaweed.

nutrient

Noun

substance an organism needs for energy, growth, and life.

Encyclopedic Entry: nutrient

photosynthesis

Noun

process by which plants turn water, sunlight, and carbon dioxide into water, oxygen, and simple sugars.

pneumatocyst

Noun

air-filled sac that makes kelp buoyant.

seaweed

Noun

marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.

stipe

Noun

stem-like stalk that supports vegetative structures such as a mushroom cap.

storm

Noun

severe weather indicating a disturbed state of the atmosphere resulting from uplifted air.

substrate

Noun

base of hard material on which a non-moving organism grows. Also called substratum.

thallus

Noun

body of some plants and plant-like organisms, not differentiated into roots, stems, or leaves.

tide

Noun

rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.

Encyclopedic Entry: tide

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Caryl-Sue, National Geographic Society

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