Algae
Algae
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diverse
simple
mostly aquatic
mostly photosynthetic
Belong to the kingdom Protista
Eukaryotic
– So they have a nucleus and membrane bound
organelles
- Photosynthesis takes place in chloroplasts
- They can be either
- Green
- Brown
- Red
How are they different from plants?
• No flowers
– Simple reproductive structures
• Lack leaves, roots, and stems
Diatoms
• Unicellular organisms that are usually
planktonic
• Cell walls made of glass-like Silica
• The glassy shell is called a frustule
– Has two halves and resembles a box
Diatom Reproduction
Frustules
get smaller
and
smaller.
Usually asexual reproduction
Ooze
• When diatoms die, their glassy shells sink
to the bottom of the ocean creating
diatomaceous ooze
• Does that sound familiar?
– Mined and used in things like
• Swimming pool filters
• Toothpaste
• Temperature and sound insulators
Dinoflagellates
• Two flagella
– one wrapped around a groove along the
middle of the cell
– One trailing behind it
– Cell wall made of plates of cellulose
Zooxanthellae
• Special dinoflagellate that lives in close
association with coral and other animals
• In coral, they photosynthesize and the
coral uses the nutrients released by them
Special Dinoflagellates
• Some are bioluminescent
• Some release toxic substances during
large blooms
Pfiesteria
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Phantom dinoflagellate
Parasite that feast on fish
Cause open sores in fish
Temporary memory loss in humans
Protozoans (animal like protists)
• Foraminiferans
– Shell made of calcium carbonate
– Pseudopodia to trap diatoms to eat
Homotrema rubrum is a
foram that is bright red and
lives on corals.
Very common in Bermuda;
skeletons made the island’s
famous pink beaches.
Radiolarians
• Spherical
• Shells of silica
• Pseudopodia to eat
Ciliates
• Many hair like extensions called cilia to
move
• Very common as freshwater Paramecium
Multicellular Algae
• Seaweed
– Sometimes called
macrophytes or macroalgae
– Also eukaryotic
– Can range from small to large
– Kelp often form large forests underwater
Structure
• Lack true leaves, stems,
and roots
• Entire body is called the
thallus
• Leaf-like flattened
portions are called
blades
• Pneumatocysts are gas
filled chambers that
keep blades close to
surface to maximize
photosynthesis
• Some seaweed
have a support
called a stipe
where blades
originate
• Holdfast holds
thallus to ground
Types of seaweed
• Green algae
– Most live in freshwater
• Brown algae
– Largest, most complex seaweeds
– Kelp
• Red algae
– More marine red than brown and green
combined
Economic Importance
• Mariculture: farming of seaweed is big in
China, Japan, and Korea
• Phycocolloids are gellatins used in many
foods
• Algin used to stabilize foods
• And much more…
Seagrasses
• Not algae
• Actually adapted land plants that live in
water
• Roots grow sideways under sediment
• Provide homes to many organisms
• Castro, Peter and Huber, Michael E.
Marine Biology. New York: McGraw-Hill,
2007.