American Oceans

Types of Seaweed

Seaweed has undoubtedly grown in popularity as more consumers seek healthier food alternatives. More people realize its nutritional value, especially its protein, mineral, and vitamin potency.

Green Seaweed

In addition, it has many industrial, medicinal, and culinary applications making its demand grow even more.

However, there are tonnes of seaweed species around the world, hence knowing the types of seaweed available is necessary. Here’s a detailed overview:

What is Seaweed?

Seaweed is a name given to various algae and marine plants growing in oceans, lakes, rivers, and other water bodies. It’s known by other names like sea vegetables, algae, kelp, and gulfweed. Typically, seaweed is divided into three groups depending on its pigmentation:

  • Red seaweed: Often known by its scientific name, Rhodophyta, the red algae is a distinct type of seaweed that lives in freshwater lakes, usually on rocky seashores. It gets the red color from the pigment called Chlorophyll A, phycoerythrin, and phycocyanin. There are 6,000 species of red seaweed
  • Brown seaweed: This seaweed grows in cold water, usually near the shoreline, and solid objects like rocky seabeds. There are 1500 species of the brown algae
  • Green seaweed: This seaweed is green because it contains Chlorophyll a and b. Chlorophyll enables the plant to absorb sunlight to transform it into food. Green seaweed can live in any ecosystem, including adverse environments and only 10% (often the sea lettuce) exists in an aquatic environment 


a close up of caulerpa seaweed

Number of species: 75

Notable species: Racemosa, Latok, Caulerpa Prolifera, Caulerpa Taxifolia, Caulerpa lentillifera

Distribution: Tropical waters like the Red Sea, the Caribbean, and Indo-Pacific

The Caulerpa seaweed is a genus of the Caulerpaceae family. These bright green algae grow as saltwater aquarium specimens.

The most common species are the Caulerpa lentillifera, also known as the sea grapes and the  Caulerpa Taxifolia often known as the killer algae. Sea grapes are common sea vegetables in tropical regions as they thrive in sandy and shallow ocean water.

The killer algae, on the other hand, is called so because of infesting thousands of acres of the seafloor in the Mediterranean Sea. It spreads on the seafloor, monopolizing the oxygen in the water, and causing marine plants like sea grass to suffocate.


fucus seaweed in the ocean

Number of species: 481

Notable species: Fucus atomarius, Fucus Ceranoides L, Fucus distichus L, Fucus Tendo L

Distribution: British Isles, California, North America (north-eastern coast)

The Fucus is a type of brown algae seaweed that lives in the intertidal zones of rocky seacoasts. It was popular among the Scottish, who used it to make soda ash.

They would harvest Fucus and other seaweed species, dry, burn, and process it to kelp, a less costly type of soda ash in Britain. It’s also a rich source of colloidal extracts with many industrial uses.


a large patch of sargassum seaweed floating in the ocean

Number of species: 300

Notable species: Sargassum fluitans, Sargassum acinarium, Sargassum polycystum, Sargassum flavicans

Distribution: Caribbean, equatorial Atlantic, Gulf of Mexico

Sargassum is brown algae that float on oceans in large island-like colonies. It develops many leafy, berry-like structures which are full of oxygen. The structures add to the plant’s buoyancy, allowing it to float on the surface.

Sargassum seaweed is a rich source of sodium alginate, a critical ingredient in thickening agents used in pharmaceutical creams and products. 

This seaweed occurs naturally, but climatic changes and human interference have caused it to accumulate on beaches, threatening the health of marine environments. 


a close up of laminaria seaweed

Number of species: 31

Notable species: Kombu, Longipes, Saccharina, Digitata, Setchellii

Distribution: Cold water coasts of Pacific and Atlantic Oceans

Laminaria is brown algae native to the Japanese. It’s a rich source of potassium, iron, and iodine like the Irish moss. The body uses iodine to produce thyroid hormones.

When combined with water, Laminaria forms a thick, sticky gel that works as a bulk laxative to relieve constipation and other digestive problems.

The seaweed is also used:

  • During childbirth, to eliminate the need for a C-section. It’s placed in the cervix to expand it and speed up labor
  •  As a supplement to enhance scalp and hair health 
  • To improve liver function
  • To promote weight loss
  • To treat food-borne bacterial diseases


a piece of sea palm seaweed washed up from the sea

Number of species: 1

Notable species: Postelsia palmaeformis

Distribution: West Coast of North America

Postelsia is the only known species of the Postelsia genus. It’s a brown seaweed that grows up to 60 cm tall and is commonly referred to as the sea palm or the palm seaweed. Postelsia is an edible seaweed as the blades and stripes can be eaten fresh, steamed, or pickled.

It’s one of the few seaweed protected from recreational harvesting. Only commercial harvesters are allowed to harvest the weed and must purchase a license.


ulva seaweed up close

Number of species: 125

Notable species:Lactuca, Ulva Lactuca

Distribution: North and South America, Indian Ocean, New Zealand, Southwest Asia, Australia

Often called sea lettuce, the Ulva is a green seaweed of the Ulvaceae family. It’s readily available and one of the most versatile seaweeds in the world.

It grows year-round to vast depths of 75 meters during summer. In addition to being edible seaweed, it can be used in pharmacology, agriculture, and medicine.


a cluster of asparagopsis seaweed waving in the current underwater

Number of species: 3

Notable species: Asparagopsis Armata, Asparagopsis Taxiformis, Asparagopsis svedelii 

Distribution: Australia

The Asparagopsis adds to our list of various types of edible seaweed. For example, the Asparagopsis taxiformis species are dried and added to poke (a fish salad) in Hawaii.

Asparagopsis is a genus of red algae, often used for medicinal applications, including making antibiotics, antibacterial and antimicrobial drugs, and cosmetics.

More recently, researchers found its ability to reduce greenhouse gasses produced by livestock. The algae contain halogen, which inhibits methane production by converting it to energy.


a lump of porphyra seaweed

Number of species: 133

Notable species: Porphyra tenera, Porphyra dentata, Porphyra yezoensis, Porphyra haitensis

Distribution: Japan, Korea, China, Ireland, Britain

Porphyra is another edible seaweed and is the most domesticated red algae. It’s native to Asian countries, where it’s used to prepare various delicacies, including sushi rolls.

Porphyra grows in cool, shallow water attaining a height of 15-30 cm in 40-50 days. The alga is also potent in Vitamin B12, making it an excellent alternative to meats.


durvillae seaweed attached to rocks

Number of species: 8

Notable species: New Zealand bull kelp, Durvillae potatorum, Durvillae incurvata 

Distribution: Macquarie Island, Coasts of Chile, Southern New Zealand

Durvillaea is another edible seaweed species. It’s popular in Chile and New Zealand, and it’s also called bull kelp seaweed due to its large and robust form. Like other algae, it has honeycomb-like structures protruding from within and is potent in vitamins, amino acids, polysaccharides, and minerals.

Seaweed is mainly used as a gastronomic ingredient for seaweed salad, soup, and side dishes. Durvillae is also used in cosmetics to improve their look and feel by reducing wrinkles and lines.


a piece of codium seaweed washed up on shore

Number of species: 50

Notable species: Codium Spongiosum, Codium repens, Codium tomentosum, Codium adhaerens

Distribution: California, South Africa, Australia, Spain’s coastal region

Commonly referred to as the dead man’s fingers. Codium is a subfamily of green algae. It’s known for its intense flavor and is therefore used for culinary purposes.

Chefs often use Codium when preparing tuna salad or vegetarian Russian salads to add the unique sea flavor without fish. It’s also an excellent companion to fruits like pineapple and raspberries and drinks like rum, whisky, vodka, and tequila. 


alaria seaweed flowing in the current underwater

Number of species: 17

Notable species: Alaria Angusta, Alaria Crispa, Alaria oblonga, Alaria fragilis

Distribution: Northern Atlantic Ocean, Norway, Channel Islands, Iceland, Britain, Netherlands, Svalbard, Ireland

Alaria adds to the many types of edible seaweed known by other names like winged kelp, dabber locks, and badderlocks. It grows to 2 m, and the frond has a distinct brown color. Alaria is rich in fiber and has a sweet flavor that makes it great to use in salads, soy sauce, and soups.

Also, its potency in vitamin B12 makes it an excellent substitute for meat in vegan diets. In addition to culinary uses, these brown algae are widely used for industrial applications like shampoos, facial masks, and conditioners due to their thickening properties.

Also, the winged kelp species contains Agar which is used in labs as a substrate for bacteria cultures.


pyropia seaweed growing on a rock

Number of species: 133

Notable species: Pyropia abbottiae, Pyropia brumalis, Pyropia vietnamensis, Pyropia perforata

Distribution: Indian Ocean, Western part of the Pacific Ocean

Pyropia is known for its nutritional value as it’s potent in protein, oligosaccharides, and vitamins. This red alga is pretty common in countries like Japan, Korea, and China, where it’s used to make nori(sushi rolls), miso soup, and seaweed salad.

Pyropia grows up to 10 meters in cool and warm-temperate waters. Upon maturity, it develops frond-like blades, which can be green, red, or brown.


a seaweed farm growing monostroma seaweed

Number of species: 32

Notable species: Angiva, nitidum, Arcticum, Grevillei, Kuroshiense

Distribution: Brazil, New Zealand, India, South Australia, Philippines, Japan, Taiwan, Korea

The Monostroma is green algae of the Monostromatacae family. Monostroma is a large, leafy plant with one cell and is potent in proteins (20%), minerals, and vitamins. It occurs naturally in the gulfs and bays of South America and East Asia, where seaweed farming is done commercially for culinary purposes.

In Japan, for example, the algae are dried and used to season dishes like okonomiyaki, a savory pancake topped with sauce, miso soup, and takoyaki, delicious octopus balls served with sauce. In other Asian regions, it is dried and boiled with soy sauce, sugar, and other ingredients to make nori-jam.


a piece of gracilaria seaweed washed up on shore

Number of species: 100+

Notable species: Salicornia, Corticata, Changii, Tikvahiae, Verrucosa, Foliifera

Distribution: All Oceans apart from the Arctic

Gracilaria is a red alga native to Asian countries like the Philippines, Vietnam, Indonesia, and Malaysia. It thrives in areas with warm and temperate waters, i.e., not less than 10 C. Gracilaria is known for its potency in agar production, contributing up to 66% of the world’s output.

And this production is likely to increase as more people venture into seaweed farming. This red alga has different uses depending on the region.

In Hawaii, it’s sold as a salad vegetable, while in the West Indies, it’s sold as sea moss or Irish moss due to its aphrodisiac properties. On the other hand, Thai people boil it and add extracted sugar to make jellies.


Is seaweed considered a superfood? 

Yes, it’s considered a superfood due to its potency in vitamins, protein, and minerals like iron. Seaweeds like Alaria are fiber-rich, while Pyropia contains oligosaccharides that improve gut health.

Do seaweeds reduce pollution?

Seaweeds can reduce pollution in many ways. Offshore seaweed aquaculture, for example, can minimize emissions from agriculture and the excess nitrogen flowing to water bodies.

How much oxygen does seaweed produce?

Studies show seaweed produces 70% of the world’s oxygen. It’s also responsible for absorbing CO2, storing nearly 175 million tonnes of carbon annually.

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