Seaweeds

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Seaweeds
The Multicellular Marine Algae
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• Seaweeds or Macroalgae are the large primary
  producers of the sea.
• Though more complex than the unicellular algae,
  seaweeds still lack the complex structures found
  in land plants.

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General Structure
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• This is a very diverse group, and although they
  lack true leaves, stems, and roots, they have a
  few common structures.

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• The complete body is called the thallus no
  matter the growth form.
• Usually, all regions of the thallus can
  photosynthesize.

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• The leaf-like flattened portions are called
  blades.
• The blades are usually the main photosynthetic
  region.These are not true leaves because they
  lack veins.

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• Most seaweeds have gas-filled bladders or floats
  that will help them maximize sunlight exposure.
  Sometime these floats contain carbon monoxide.

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• Some seaweeds have a stem-like structure called
  the stipe. This structure is not found on all
  seaweeds.

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• The stipe provides support and can be long and
  tough, as in the Giant Kelp.
• The stipe also allows a place for the attachment
  of the blades.

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• A holdfast is a root-like structure that holds
  the seaweed to the bottom. This structure does
  not aid in gathering nutrients.

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• The holdfast does not penetrate through sand or
  mud, so like this Sea Palm, most macroalgae are
  only found on hard sediments.

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Types ofMacroalgae
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The are three types of macroalgae
Green
and
Red
Brown
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Green Algae

• About 700 of the 7,000 species of green algae
  are marine. Of those, few are multicellular.

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Green Algae

• Green algae can be very common where the
  salinities vary a lot. ( Bays, Estuaries,
  Tide Pools)

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Green Algae

• They are usually bright green because the
  chlorophyll is not masked by other pigments.

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Green Algae

• Green algae have a simple thallus when compared
  to red and brown algae.

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Green Algae

• Many forms are filamentous or form paper-thin
  sheets.

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Green Algae

• Others form spongy fingers as in this example of
  Dead Mans Fingers.

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Brown Algae

• Almost all species of brown algae are marine.
  The best know and the most complex are the kelps.

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Brown Algae

• Color varies from olive green to dark brown
  because there are many yellow-brown pigments that
  mask the color of chlorophyll.

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Brown Algae

• Besides the well known kelps, Sargasso weed is
  also a well known brown algae.

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Brown Algae

• Sargasso weed often forms into large mats in the
  mid Atlantic where unique animals and communities
  can be found.

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Brown Algae

• Notice anything here?
• Can you see the Sargassum Angler Fish?

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Red Algae

• There are more species of marine red algae than
  green or brown.
• Most are actually red!

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Red Algae

• Some red algae have calcium carbonate within
  their cell walls.
• These, help form coral reefs.

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How about a quick quiz?

1. The entire body of the seaweed is called the
   _____.
2. What is another name for seaweeds?
3. Name the 3 types of seaweeds.

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• 4. What is the stem-like structure called?
• 5. Which type of seaweed can be important in the
  formation of a coral reef?

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Answers

• Macroalgae
• Thallus
• Red, Green, and Brown
• Stipe
• 5. Red