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# What is seaweed?

## "Seaweed" is the common name for countless species of marine plants and algae that grow in the ocean as well as in rivers, lakes, and other water bodies.

Kelp forest in the Channel Islands National Marine Sanctuary and National Park.

Some seaweeds are microscopic, such as the  phytoplankton that live suspended in the water column and provide the  base for most marine food chains. Some are enormous, like the giant kelp that grow  in abundant “forests” and tower like underwater redwoods from their roots at  the bottom of the sea. Most are medium-sized, come in colors of red, green, brown,  and black, and randomly wash up on beaches and shorelines just  about everywhere.

The vernacular “seaweed” is a bona-fide misnomer, because a  weed is a plant that spreads so profusely it can harm the habitat where it  takes hold. (Consider kudzu, the infamous “mile-a-minute vine” that chokes  waterways throughout the U.S. Southeast). Not only are the fixed and free-floating  “weeds” of the sea utterly essential to innumerable marine creatures, both as  food and as habitat, they also provide many benefits to land-dwellers, notably  those of the human variety.

            - Seaweed is chock-full of vitamins, minerals, and  fiber, and can be tasty. For at least 1,500 years, the Japanese have enrobed a  mixture of raw fish, sticky rice, and other ingredients in a seaweed called  nori. The delectable result is a sushi roll. 
            - Many seaweeds contain anti-inflammatory and  anti-microbial agents. Their known medicinal effects have been legion for  thousands of years; the ancient Romans  used them to t reat wounds, burns, and  rashes. Anecdotal evidence also suggests that the ancient Egyptians may have  used them as a treatment for breast cancer. 
            - Certain seaweeds do, in fact, possess powerful  cancer-fighting agents that researchers hope will eventually prove effective in  the treatment of malignant tumors and leukemia in people. While dietary soy was  long credited for the low rate of cancer in Japan, this indicator of robust  health is now attributed to dietary seaweed. 
            - These versatile marine plants and algae have  also contributed to economic growth. Among their many uses in manufacturing,  they are effective binding agents (emulsifiers) in such commercial goods as  toothpaste and fruit jelly, and popular softeners (emollients) in organic cosmetics  and skin-care products.            

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          - Seaweeds (Olympic Coast National Marine Sanctuary)
          - What is a kelp forest?

**Last updated:**   01/18/24**Author:** NOAAHow to cite this article

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