What Are Brown Algae?

Some species offer health benefits when consumed by humans or animals

Seaweed- Ascophyllum nodosum - Brown Algae - Rockweed, Norwegian kelp, Knotted kelp, Knotted wrack, Egg wrack
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Brown algae are the largest and most complex type of marine algae. They get their name from their brown, olive, or yellowish-brown color, which comes from the pigment called fucoxanthin. This pigment is not found in other algae or in plants such as red or green algae, and as a result, brown algae are in the kingdom Chromista.

Brown algae are often rooted to a stationary structure such as a rock, a shell or a dock by structures called holdfasts, although species in the genus Sargassum are free-floating. Many species of brown algae have air bladders that help the blades of the algae float toward the ocean surface, allowing for maximum sunlight absorption.

As with other algae, the distribution of brown algae is broad, from tropical to polar zones. Brown algae can be found in intertidal zones, near coral reefs, and in deeper waters.A National Oceanic and Atmospheric Administration (NOAA) study notes them at 165 feet in the Gulf of Mexico.


The taxonomy of brown algae can be confusing, as brown algae can be classified into the phylum Phaeophyta or Heterokontophyta, depending on what you read. Much information on the subject refers to brown algae as phaeophytes, but according to AlgaeBase, brown algae are in the phylum Heterokontophyta and class Phaeophyceae.

About 1,800 species of brown algae exist. The largest and among the best known is kelp. Other examples of brown algae include seaweeds in the genus Fucus, commonly known as "rockweed" or "wracks," and in the genus Sargassum, which form floating mats and are the most prominent species in the area known as the Sargasso Sea, which is in the middle of the North Atlantic Ocean.

Kelp, Fucales, Dictyotales, Ectocarpus, Durvillaea Antarctica, and Chordariales are all examples of brown algae, but each belongs to a different classification determined by their individual attributes and features.

Natural and Human Uses

Kelp and other brown algae provide a number of health benefits when they are consumed by humans and animals. Brown algae are eaten by herbivorous organisms such as fish, gastropods and sea urchins. Benthic (bottom-dwelling) organisms also utilize brown algae such as kelp when pieces of it sink to the sea floor to decompose.

Humans find a variety of commercial uses for these marine organisms. Brown algae are used to produced alginates, which are employed as food additives and in industrial manufacturing. Their common uses include as food thickeners and fillers as well as stabilizers for the ionization process of batteries.

According to some medical research, several chemicals found in brown algae can work as antioxidants, which are thought to prevent damage to the human body. Brown algae can also be used as a cancer suppressant as well as an anti-inflammatory and immunity booster.

These algae provide not only food and commercial utility; they also provide valuable habitat for certain species of marine life and significantly offset carbon dioxide emissions through the photosynthesis processes of certain populous species of kelp.

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Kennedy, Jennifer. "What Are Brown Algae?" ThoughtCo, Aug. 26, 2020, thoughtco.com/brown-algae-phaeophyta-2291972. Kennedy, Jennifer. (2020, August 26). What Are Brown Algae? Retrieved from https://www.thoughtco.com/brown-algae-phaeophyta-2291972 Kennedy, Jennifer. "What Are Brown Algae?" ThoughtCo. https://www.thoughtco.com/brown-algae-phaeophyta-2291972 (accessed May 29, 2023).