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Red Algae (Rhodophyta)


Rhodophyta seaweed
Jonelle Weaver/ The Image Bank/ Getty Images


Red algae are, not surprisingly, red, reddish or purplish in color. There are about 6,000 species of red algae (Source: AlgaeBase), and they are protists in the phylum Rhodophyta. Red algae species range from simple one-celled organisms to complex, multi-celled, plant-like organisms. Red algae get their energy from photosynthesis. One thing that distinguishes red algae from other algae is that their cells lack flagella.

How Does Red Algae Get Its Color?:

When you think of algae, you might think of something that is green or brownish green. So what gives red algae their color?

Red algae contain a variety of pigments, including cholorophyll a, phycobiliproteins, red phycoerythrin, blue phycocyanin, carotenes, lutein, and zeaxanthin. The most important pigment is phycoerythrin, which provides the algae's red pigmentation by reflecting red light and absorbing blue light. Red algae with little of this pigment may appear more green or blue than red due to the other pigments in this algae.

Because red algae contains pigments that absorb blue light waves, it can be found deeper in the ocean than some other algaes.

Habitat and Distribution:

Red algae are found around the world from polar to tropical waters, and are commonly found in tide pools and in coral reefs.


  • Kingdom: Protista
  • Phylum: Rhodophyta

Red Algae Species:

Some common examples of red algae include Irish moss, dulse, laver (nori), and coralline algae.

Coralline algae is a type of red algae that helps build tropical coral reefs. Coralline algae secretes calcium carbonate to build a hard shell around its cell walls. There are both upright forms of coralline algae, which look very similar to coral, and encrusting forms which grows as a mat over hard structures such as rocks and the shells of organisms like clams and snails. Bubble gum algae is an example of an encrusting algae, and with its pink coloration, looks like discarded bubble gum.

Natural and Human Uses:

  • Red algae are eaten by fish, crustaceans, worms and gastropods.
  • Red algae are also eaten by humans. Two examples are nori, which is used in sushi, and Irish moss, which can be made into pudding.
  • Red algae are used to produce agars, which are gelatinous substances used as a food additive and in science labs as a culture medium.
  • Red algae is also promoted by supplements distributors to treat the herpes simplex virus.


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