Seaweed, or macroalgae, refers to thousands of species of

macroscopic The macroscopic scale is the length scale on which objects or phenomena are large enough to be visible with the naked eye, without magnifying optical instruments. It is the opposite of microscopic. Overview When applied to physical phenome ...

multicellular A multicellular organism is an organism that consists of more than one cell (biology), cell, unlike unicellular organisms. All species of animals, Embryophyte, land plants and most fungi are multicellular, as are many algae, whereas a few organism ...

, marine

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

. The term includes some types of ''

Rhodophyta Red algae, or Rhodophyta (, ; ), make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest phyla of algae, containing over 7,000 recognized species within over 900 genera amidst ongoing taxonomic revisions. ...

'' (red), '' Phaeophyta'' (brown) and ''

Chlorophyta Chlorophyta is a division of green algae informally called chlorophytes. Description Chlorophytes are eukaryotic organisms composed of cells with a variety of coverings or walls, and usually a single green chloroplast in each cell. They are ...

'' (green) macroalgae. Seaweed species such as

kelp Kelps are large brown algae or seaweeds that make up the order (biology), order Laminariales. There are about 30 different genus, genera. Despite its appearance and use of photosynthesis in chloroplasts, kelp is technically not a plant but a str ...

s provide essential nursery habitat for fisheries and other marine species and thus protect food sources; other species, such as

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic algae, play a vital role in capturing carbon and producing at least 50% of Earth's oxygen. Natural seaweed ecosystems are sometimes under threat from human activity. For example, mechanical

dredging Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing d ...

of kelp destroys the resource and dependent fisheries. Other forces also threaten some seaweed ecosystems; for example, a

wasting disease In medicine, wasting, also known as wasting syndrome, refers to the process by which a debilitating disease causes muscle and fat tissue to "waste" away. Wasting is sometimes referred to as "acute malnutrition" because it is believed that episo ...

in predators of

purple urchin ''Strongylocentrotus purpuratus'' is a species of sea urchin in the Family (biology), family Strongylocentrotidae commonly known as the purple sea urchin. It lives along the eastern edge of the Pacific, Pacific Ocean extending from Ensenada, B ...

s has led to an urchin population surge which has destroyed large

kelp forest Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on E ...

regions off the coast of California. Humans have a long history of cultivating seaweeds for their uses. In recent years,

seaweed farming Seaweed farming or kelp farming is the practice of aquaculture, cultivating and harvesting seaweed. In its simplest form farmers gather from natural beds, while at the other extreme farmers fully control the crop's biological life cycle, life c ...

has become a global agricultural practice, providing food, source material for various chemical uses (such as

carrageenan Carrageenans or carrageenins ( ; ) are a family of natural linear sulfation, sulfated polysaccharides. They are extracted from red algae, red edible seaweeds. Carrageenans are widely used in the food industry, for their gelling, thickening, an ...

), cattle feeds and fertilizers. Due to their importance in marine ecologies and for absorbing carbon dioxide, recent attention has been on cultivating seaweeds as a potential

climate change mitigation Climate change mitigation (or decarbonisation) is action to limit the greenhouse gases in the atmosphere that cause climate change. Climate change mitigation actions include energy conservation, conserving energy and Fossil fuel phase-out, repl ...

strategy for biosequestration of carbon dioxide, alongside other benefits like

nutrient pollution Nutrient pollution is a form of water pollution caused by too many Nutrient, nutrients entering the water. It is a primary cause of eutrophication of surface waters (lakes, rivers and Coast, coastal waters), in which excess nutrients, usually ni ...

reduction, increased habitat for coastal aquatic species, and reducing local

ocean acidification Ocean acidification is the ongoing decrease in the pH of the Earth's ocean. Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ...

. The

IPCC The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to "provide governments at all levels with scientific information that they can use to develop climate policies". The World M ...

Special Report on the Ocean and Cryosphere in a Changing Climate The United Nations' Intergovernmental Panel on Climate Change's (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) is a report about the effects of climate change on the Ocean, world's seas, sea ice, Ice cap, icecaps ...

recommends "further research attention" as a mitigation tactic.

Taxonomy

"Seaweed" lacks a formal definition, but seaweed generally lives in the ocean and is visible to the naked eye. The term refers to both flowering plants submerged in the ocean, like

eelgrass Eelgrass is a common name for several plants and may refer to: * '' Zostera'', marine eelgrass * '' Vallisneria'', freshwater eelgrass See also *'' Potamogeton compressus'', known as eel-grass pondweed {{Short pages monitor

Biogeographic expansion

Nowadays a number of vectors—e.g., transport on ship hulls, exchanges among shellfish farmers, global warming, opening of trans-oceanic canals—all combine to enhance the transfer of exotic seaweeds to new environments. Since the piercing of the Suez Canal, the situation is particularly acute in the Mediterranean Sea, a 'marine biodiversity hotspot' that now registers over 120 newly introduced seaweed species -the largest number in the world.

Production

As of 2019, 35,818,961 tonnes were produced, of which 97.38% were produced in Asian countries.

Farming

Uses

Seaweed has a variety of uses, for which it is farmed or foraged.

Food

Seaweed is consumed across the world, particularly in

East Asia East Asia is a geocultural region of Asia. It includes China, Japan, Mongolia, North Korea, South Korea, and Taiwan, plus two special administrative regions of China, Hong Kong and Macau. The economies of Economy of China, China, Economy of Ja ...

, e.g.,

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

and

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

, e.g.

Brunei Brunei, officially Brunei Darussalam, is a country in Southeast Asia, situated on the northern coast of the island of Borneo. Apart from its coastline on the South China Sea, it is completely surrounded by the Malaysian state of Sarawak, with ...

Singapore Singapore, officially the Republic of Singapore, is an island country and city-state in Southeast Asia. The country's territory comprises one main island, 63 satellite islands and islets, and one outlying islet. It is about one degree ...

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

Burma Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and ha ...

Cambodia Cambodia, officially the Kingdom of Cambodia, is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. It is bordered by Thailand to the northwest, Laos to the north, and Vietnam to the east, and has a coastline ...

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

, the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

, and

Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...

, as well as in

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

Belize Belize is a country on the north-eastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a maritime boundary with Honduras to the southeast. P ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

, the

Canadian Maritimes The Maritimes, also called the Maritime provinces, is a region of Eastern Canada consisting of three provinces: New Brunswick, Nova Scotia, and Prince Edward Island. The Maritimes had a population of 1,899,324 in 2021, which makes up 5.1% of ...

Scandinavia Scandinavia is a subregion#Europe, subregion of northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. ''Scandinavia'' most commonly refers to Denmark, Norway, and Sweden. It can sometimes also ...

South West England South West England, or the South West of England, is one of the nine official regions of England, regions of England in the United Kingdom. Additionally, it is one of four regions that altogether make up Southern England. South West England con ...

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

and

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, and

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

. Gim (김, Korea),

nori Nori is a dried edible seaweed used in Japanese cuisine, usually made from species of the red algae genus ''Pyropia'', including ''P. yezoensis'' and ''Pyropia tenera, P. tenera''. It has a strong and distinctive flavor, and is generally made in ...

(, Japan) and

zicai ''Porphyra'' is a genus of coldwater seaweeds that grow in cold, shallow seawater. More specifically, it belongs to red algae phylum of laver species (from which comes laverbread), comprising approximately 70 species.Brodie, J.A. and Irvine, L. ...

(, China) are sheets of dried ''

Porphyra ''Porphyra'' is a genus of coldwater seaweeds that grow in cold, shallow seawater. More specifically, it belongs to red algae phylum of laver species (from which comes laverbread), comprising approximately 70 species.Brodie, J.A. and Irvine, L ...

'' used in soups,

sushi is a traditional Japanese dish made with , typically seasoned with sugar and salt, and combined with a variety of , such as seafood, vegetables, or meat: raw seafood is the most common, although some may be cooked. While sushi comes in n ...

or ''

onigiri , also known as or , is a Japanese cuisine, Japanese rice ball made from white rice. It is usually formed into triangular or cylindrical shapes, and wrapped in ''nori'' (seaweed). Onigiri traditionally have sour or salty fillings such as ''um ...

'' (rice balls). ''

Gamet Gamet is a traditional dried edible seaweed from Ilocos Norte and Cagayan of the Philippines, particularly from the town of Burgos, Ilocos Norte, Burgos. Gamet are dried into sheets or thin cakes called (from Spanish for "piece"), which are cha ...

'' in the Philippines, from dried ''

Pyropia ''Pyropia'' is a genus of red algae in the family Bangiaceae. It is found around the world in intertidal zones and shallow water. The genus has folding frond-like blades which are either red, brown or green. Some ''Pyropia'' species are used to ...

'', is also used as a flavoring ingredient for soups, salads and

omelette An omelette (sometimes omelet in American English; see spelling differences) is a dish made from eggs (usually chicken eggs), fried with butter or oil in a frying pan. It is a common practice for an omelette to include fillings such as chiv ...

s. ''

Chondrus crispus ''Chondrus crispus''—commonly called Irish moss or carrageenan moss (Irish ''carraigín'', "little rock")—is a species of red algae which grows abundantly along the rocky parts of the Atlantic coasts of Europe and North America. In its fresh ...

'' ('Irish moss' or

moss) is used in food additives, along with ''

Kappaphycus ''Kappaphycus'' is a genus of red algae. Species are distributed in the waters of East Africa, Indonesia, Malaysia, Hainan Island, the Philippines, and Micronesia.Guiry, M. D. In: Guiry, M. D. & G. M. Guiry. 2013''Kappaphycus''.AlgaeBase. Nationa ...

'' and G''igartinoid'' seaweed. ''Porphyra'' is used in

to make

laverbread Laverbread (; or '; ) is a food product made from laver, an edible seaweed (littoral alga) consumed mainly in Wales as part of local traditional cuisine. The seaweed is commonly found around the west coast of Great Britain, and the coasts of I ...

(sometimes with

oat The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural). Oats appear to have been domesticated as a secondary crop, as their seeds ...

flour). In northern

, seaweed is mixed with

milk Milk is a white liquid food produced by the mammary glands of lactating mammals. It is the primary source of nutrition for young mammals (including breastfeeding, breastfed human infants) before they are able to digestion, digest solid food. ...

nutmeg Nutmeg is the seed, or the ground spice derived from the seed, of several tree species of the genus '' Myristica''; fragrant nutmeg or true nutmeg ('' M. fragrans'') is a dark-leaved evergreen tree cultivated for two spices derived from its fru ...

cinnamon Cinnamon is a spice obtained from the inner bark of several tree species from the genus ''Cinnamomum''. Cinnamon is used mainly as an aromatic condiment and flavouring additive in a wide variety of cuisines, sweet and savoury dishes, biscuits, b ...

and

vanilla Vanilla is a spice derived from orchids of the genus ''Vanilla (genus), Vanilla'', primarily obtained from pods of the flat-leaved vanilla (''Vanilla planifolia, V. planifolia''). ''Vanilla'' is not Autogamy, autogamous, so pollination ...

to make "" ("sweet").

Alginate Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous gum when hydrated. When the alginic acid binds with sodium and calcium ions, the resulting salts are k ...

agar Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from " ogonori" and " tengusa". As found in nature, agar is a mixture of two components, t ...

and

are gelatinous seaweed products collectively known as

hydrocolloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others exten ...

s or phycocolloids. Hydrocolloids are food additives. The food industry exploits their gelling, water-retention, emulsifying and other physical properties. Agar is used in foods such as confectionery, meat and poultry products, desserts and beverages and moulded foods. Carrageenan is used in salad dressings and sauces, dietetic foods, and as a preservative in meat and fish, dairy items and baked goods. Seaweeds are used as animal feeds. They have long been grazed by sheep, horses and cattle in Northern Europe, even though their nutritional benefits are questionable. Their protein content is low and their heavy metal content is high, especially for arsenic and iodine, which are respectively toxic and nutritious. They are valued for fish production. Adding seaweed to livestock feed can substantially reduce

methane emissions Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% (360 million tons) of methane r ...

from cattle, but only from their feedlot emissions. As of 2021, feedlot emissions account for 11% of overall emissions from cattle.

Medicine and herbs

Alginates are used in wound dressings (see

alginate dressing An alginate dressing is a natural wound dressing derived from carbohydrate sources released by clinical bacterial species, in the same manner as biofilm formation. These types of dressings are best used on wounds that have a large amount of exudat ...

), and dental moulds. In

microbiology Microbiology () is the branches of science, scientific study of microorganisms, those being of unicellular organism, unicellular (single-celled), multicellular organism, multicellular (consisting of complex cells), or non-cellular life, acellula ...

is used as a culture medium. Carrageenans, alginates and agaroses, with other macroalgal polysaccharides, have

biomedicine Biomedicine (also referred to as Western medicine, mainstream medicine or conventional medicine)

applications. ''Delisea pulchra'' may interfere with bacterial colonization. Sulfated saccharides from red and green algae inhibit some

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

and

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

-enveloped

virus A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...

es. Seaweed extract is used in some diet pills. Other seaweed pills exploit the same effect as gastric banding, expanding in the stomach to make the stomach feel more full.

Paper and packaging

Seaweed can be used for packaging, such as via being made into a rigid plastic alternative, while seaweed pulp can be used to make paper.

Climate change mitigation

Seaweed is a renewable resource.

Other uses

Other seaweed may be used as

fertilizer A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by Decomposition, decomposing plant and food waste, recycling organic materials, and man ...

for landscaping, or to combat

beach erosion Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of waves, currents, tides, wind-driven water, waterborne ice, or other impacts of storms. The landward r ...

through burial in beach dunes. Seaweed is under consideration as a potential source of

bioethanol Ethanol fuel is fuel containing ethyl alcohol, the same type of alcohol as found in alcoholic beverages. It is most often used as a motor fuel, mainly as a biofuel additive for gasoline. Several common ethanol fuel mixtures are in use a ...

. Alginates are used in industrial products such as paper coatings, adhesives, dyes, gels, explosives and in processes such as paper sizing, textile printing, hydro-mulching and drilling. Seaweed is an ingredient in toothpaste, cosmetics and paints. Seaweed is used for the production of bio yarn (a textile). Several of these resources can be obtained from seaweed through biorefining. Seaweed collecting is the process of collecting, drying and pressing seaweed. It was a popular pastime in the Victorian era and remains a hobby today. In some emerging countries, seaweed is harvested daily to support communities. Harvesting seaweed in Jambiani

Seaweed is sometimes used to build roofs on houses on

Læsø Læsø ("Isle of Ægir, Hlér") is the largest island in the North Sea bay of Kattegat, and is located off the northeast coast of the Jutland Peninsula, the Denmark, Danish mainland. Læsø is also the name of the municipality (Danish language, D ...

Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...

. File:Onigiri at an onigiri restaurant by zezebono in Tokyo.jpg, ''

Onigiri , also known as or , is a Japanese cuisine, Japanese rice ball made from white rice. It is usually formed into triangular or cylindrical shapes, and wrapped in ''nori'' (seaweed). Onigiri traditionally have sour or salty fillings such as ''um ...

'' and ''

wakame Wakame ''(Undaria pinnatifida)'' is a species of kelp native to cold, temperate coasts of the northwest Pacific Ocean. As an edible seaweed, it has a subtly sweet, but distinctive and strong flavour and satiny texture. It is most often served in ...

'' ''

miso soup is a traditional Japan, Japanese soup consisting of miso paste mixed with a ''dashi'' Stock (food), stock. It is commonly served as part of an meal, meaning "one soup, three dishes," a traditional Japanese meal structure that includes rice, sou ...

'', Japan File: Laver and toast.JPG,

Laverbread Laverbread (; or '; ) is a food product made from laver, an edible seaweed (littoral alga) consumed mainly in Wales as part of local traditional cuisine. The seaweed is commonly found around the west coast of Great Britain, and the coasts of I ...

and toast File: Seaweed Farms in Indonesia.jpg, alt=Photo of near-shore ocean, divided into rectangles, most containing a yards-long, narrow boat, Small plots being used to farm seaweed in

, with each rectangle belonging to a different family

Health risks

Rotting seaweed is a potent source of

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

, a highly toxic gas, and has been implicated in some incidents of apparent hydrogen sulfide poisoning. It can cause vomiting and diarrhea. The so-called "stinging seaweed" '' Microcoleus lyngbyaceus'' is a filamentous

cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

which contains toxins including lyngbyatoxin-a and debromoaplysiatoxin. Direct skin contact can cause

seaweed dermatitis ''Lyngbya majuscula'' is a species of filamentous cyanobacteria in the genus '' Lyngbya''. It is named after the Dane Hans Christian Lyngbye. As a result of recent genetic analyses, several new genera were erected from the genus ''Lyngbya'': ...

characterized by painful, burning lesions that last for days.

Threats

Bacterial disease

ice-ice Ice-ice is a disease condition of seaweed. Ice-ice is caused when changes in salinity, Sea surface temperature, ocean temperature and irradiance, light intensity cause stress to seaweeds, making them produce a "moist organic substance" that attra ...

infects ''Kappaphycus'' (red seaweed), turning its branches white. The disease caused heavy crop losses in the Philippines, Tanzania and Mozambique. Sea urchin barrens have replaced kelp forests in multiple areas. They are "almost immune to starvation". Lifespans can exceed 50 years. When stressed by hunger, their jaws and teeth enlarge, and they form "fronts" and hunt for food collectively.

References

External links

Michael Guiry's Seaweed Site
information on all aspects of algae, seaweed and marine algal biology
SeaweedAfrica
information on seaweed utilisation for the African continent.

* ttps://www.algaebase.org/ AlgaeBase a searchable taxonomic, image, and utilization database of freshwater, marine and terrestrial algae, including seaweed. {{Authority control Blue carbon Edible algae Polyphyletic groups

Weed A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. Pla ...