Algae are autotrophic, unicellular protists.
Seaweeds are multicellular green, brown,
and red algae (protists)
• What is Seaweed? It is not a plant!!!
• Seaweeds, as its name suggests is a loose colloquial term
encompassing macroscopic, multicellular, benthic marine
algae. The term includes some members of the red, brown
and green algae.
• Seaweeds are extensively used as food by coastal people
around the world. They are either eaten raw, cooked or
processed. Seaweeds are also being used as medicine and
other medical applications (like treating cancer).
• Red seaweeds are extensively farmed and produced in the
Philippines. Red seaweeds are the raw materials that
produces Carrageenan, a jelly substance used as food
additive or ingredient to thicken products such as instant
puddings and ice cream.
 Seaweeds are primary producers using light energy to
perform photosynthesis. There are a few seaweeds
that are parasitic on other seaweeds.
 Seaweeds lack the highly specialized structures and
reproductive mechanisms of land plants.
 The variation among seaweeds is spectacular.
 Thallus - The complete body, whether it is a filament, a
thin leafy sheet, a crusty cushion or a giant kelp.
 Blade - The leaf-like, flattened portions of the thallus.
Not leaves because it has no veins.
The blades increase the surface area and are the main
photosynthetic region of the seaweed.
 Pneumatocysts – gas-filled bladder that keeps the blades
floating near to the surface for maximum light exposure.
 Stipe – a distinct stem-like structure that provides
support from which the blades originate.
 Holdfast – looks like roots, but they do not absorb
significant amounts of water or nutrients, or penetrate
the sand or mud. The holdfast anchors the seaweed to
the rocks, and are well-developed in the kelps.
Seaweed Farms in Indonesia
Diver in Kelp Forest
Macrocystis-Giant Kelp
Diver with Bull Kelp
Red Algae
Red Algae
Red Algae