• 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.

    1. What is a stipe?

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

    2. What is a pneumatocyst?

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

    3. What is a blade?

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

    4. What is a holdfast?

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

    5. What is a thallus?

      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?

      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?

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

  • Term Part of Speech Definition Encyclopedic Entry
    blade Noun

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

    buoyant Adjective

    capable of floating.

    canopy Noun

    one of the top layers 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

    characteristic to or of a specific place.

    Encyclopedic Entry: indigenous
    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