Seaweed

{{about|the aquatic plant-like algae|its culinary uses|Edible seaweed|the similarly-named plant|Seagrass|other uses}}

{{Paraphyletic group |auto=yes

| parent = Eukaryota

|subheader=Informal group of macroscopic marine algae

|image= Fucus serratus 2015-09-08 ag M0010140.jpg

|image_alt="Fucus serratus"

|image_caption=Fucus serratus

|includes_text=Seaweeds can be found in the following groups

|includes=

Chlorophyta (green algae)

Phaeophyceae (brown algae)
Phaeothamniophyceae
Chrysophyceae (gold algae)
Cyanobacteria{{cite book |author1=James, William D. |author2=Berger, Timothy G. |title=Andrews' Diseases of the Skin: clinical Dermatology |publisher=Saunders Elsevier |year=2006 |isbn=978-0-7216-2921-6 |display-authors=etal}}
Rhodophyta (red algae)

}}

File:Ascophyllum nodosum.jpg exposed to the sun in Nova Scotia, Canada|alt=Photo of seaweed with small swollen areas at the end of each frond]]

File:codiumfragile.jpg) off the Massachusetts coast in the United States|alt=Photo of detached seaweed frond lying on sand]]

File:Kelp forest Otago 1s.JPG in Otago, New Zealand|alt=Photo of seaweed with the tip floating at the surface]]

Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of Rhodophyta (red), Phaeophyta (brown) and Chlorophyta (green) macroalgae. Seaweed species such as kelps provide essential nursery habitat for fisheries and other marine species and thus protect food sources; other species, such as planktonic algae, play a vital role in capturing carbon and producing at least 50% of Earth's oxygen.{{cite web |title=How much oxygen comes from the ocean? |website=National Ocean Service |publisher=National Oceanic and Atmospheric Administration |url=https://oceanservice.noaa.gov/facts/ocean-oxygen.html |access-date=23 November 2021}}

Natural seaweed ecosystems are sometimes under threat from human activity. For example, mechanical dredging of kelp destroys the resource and dependent fisheries. Other forces also threaten some seaweed ecosystems; for example, a wasting disease in predators of purple urchins has led to an urchin population surge which has destroyed large kelp forest regions off the coast of California.{{Cite web|title=California's crashing kelp forest|url=https://phys.org/news/2019-10-california-kelp-forest.html|access-date=2021-02-24|website=phys.org|language=en}}

Humans have a long history of cultivating seaweeds for their uses. In recent years, seaweed farming has become a global agricultural practice, providing food, source material for various chemical uses (such as carrageenan), 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 strategy for biosequestration of carbon dioxide, alongside other benefits like nutrient pollution reduction, increased habitat for coastal aquatic species, and reducing local ocean acidification.{{Cite journal|last1=Duarte|first1=Carlos M.|last2=Wu|first2=Jiaping|last3=Xiao|first3=Xi|last4=Bruhn|first4=Annette|last5=Krause-Jensen|first5=Dorte|date=2017|title=Can Seaweed Farming Play a Role in Climate Change Mitigation and Adaptation?|journal=Frontiers in Marine Science|language=en|volume=4|doi=10.3389/fmars.2017.00100|issn=2296-7745|doi-access=free}} The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate recommends "further research attention" as a mitigation tactic.{{Cite book|last1=Bindoff|first1=N. L.|title=IPCC Special Report on the Ocean and Cryosphere in a Changing Climate|last2=Cheung|first2=W. W. L.|last3=Kairo|first3=J. G.|last4=Arístegui|first4=J.|last5=Guinder|first5=V. A.|last6=Hallberg|first6=R.|last7=Hilmi|first7=N. J. M.|last8=Jiao|first8=N.|last9=Karim|first9=Md S.|year=2019|pages=447–587|chapter=Chapter 5: Changing Ocean, Marine Ecosystems, and Dependent Communities|ref={{harvid|IPCC SROCC Ch5|2019}} |display-authors=4|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/3/2019/11/09_SROCC_Ch05_FINAL.pdf|first10=L.|last16=Williamson|first16=P.|last15=Tagliabue|first15=A.|last14=Suga|last12=Purca Cuicapusa|last13=Rinkevich|first13=B.|first12=S. R.|last11=O'Donoghue|first11=S.|last10=Levin|first14=T.}}

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, as well as larger marine algae. Generally, it is one of several groups of multicellular algae; red, green and brown.{{Cite web |date=2019-06-15 |title=5.4: Algae |url=https://bio.libretexts.org/Courses/Portland_Community_College/Cascade_Microbiology/05%3A_The_Eukaryotes_of_Microbiology/5.4%3A_Algae |access-date=2024-02-10 |website=Biology LibreTexts |language=en}} They lack one common multicellular ancestor, forming a polyphyletic group. In addition, blue-green algae (Cyanobacteria) are occasionally considered in seaweed literature.{{cite journal |last1=Lobban |first1=Christopher S. |last2=Harrison |first2=Paul J. |title=Morphology, life histories, and morphogenesis |journal=Seaweed Ecology and Physiology |date=1994 |pages=1–68 |doi=10.1017/CBO9780511626210.002 |isbn=9780521408974 |url=https://www.cambridge.org/core/books/seaweed-ecology-and-physiology/morphology-life-histories-and-morphogenesis/9359C9B0571E8E75645CBA3C10D9AD58}}

The number of seaweed species is still a topic of discussion among scientists, but it is most likely that there are several thousand species of seaweed.{{cite book |last1=Townsend |first1=David W. |title=Oceanography and Marine Biology: An Introduction to Marine Science |date=March 2012 |publisher=Oxford University Press Inc |isbn=9780878936021}}

= Genera =

File:Claudea elegans tetrasporangia.jpg

The following table lists a very few example genera of seaweed.

class="wikitable" ! Genus		Algae Phylum	Remarks
Caulerpa	100px	Green	Submerged.
Fucus	150px	Brown	In intertidal zones on rocky shores.
Gracilaria	150px	Red	Cultivated for food.
Laminaria	100px	Brown	Also known as kelp 8–30 m under water and cultivated for food.
Macrocystis	150px	Brown	Giant kelp forming floating canopies.
Monostroma	150px	Green
Porphyra	150px	Red	Intertidal zones in temperate climate and cultivated for food.
Sargassum	150px	Brown	Pelagic especially in the Sargasso Sea.

Anatomy

Seaweed's appearance resembles non-woody terrestrial plants. Its anatomy includes:{{Cite web|url=https://www.easterncapescubadiving.co.za/index.php?page_name=more&list_id=158|title=seaweed menu|website=www.easterncapescubadiving.co.za|access-date=2019-04-28|archive-date=2020-02-17|archive-url=https://web.archive.org/web/20200217082733/https://www.easterncapescubadiving.co.za/index.php?page_name=more&list_id=158|url-status=dead}}{{Cite web |date=2017-02-06 |title=The Science of Seaweeds |url=https://www.americanscientist.org/article/the-science-of-seaweeds |access-date=2022-06-02 |website=American Scientist |language=en}}

Thallus: algal body
Lamina or blade: flattened structure that is somewhat leaf-like
Sorus: spore cluster
pneumatocyst, air bladder: a flotation-assisting organ on the blade
Kelp, float: a flotation-assisting organ between the lamina and stipe
Stipe: stem-like structure, may be absent
Holdfast: basal structure providing attachment to a substrate
Haptera: finger-like extension of the holdfast that anchors to a benthic substrate

The stipe and blade are collectively known as the frond.

Ecology

File: NSW seabed 2.JPG

Two environmental requirements dominate seaweed ecology. These are seawater (or at least brackish water) and light sufficient to support photosynthesis. Another common requirement is an attachment point, and therefore seaweed most commonly inhabits the littoral zone (nearshore waters) and within that zone, on rocky shores more than on sand or shingle. In addition, there are few genera (e.g., Sargassum and Gracilaria) which do not live attached to the sea floor, but float freely.

Seaweed occupies various ecological niches. At the surface, they are only wetted by the tops of sea spray, while some species may attach to a substrate several meters deep. In some areas, littoral seaweed colonies can extend miles out to sea.{{cn|date=June 2024}} The deepest living seaweed are some species of red algae. Others have adapted to live in tidal rock pools. In this habitat, seaweed must withstand rapidly changing temperature and salinity and occasional drying.Lewis, J. R. 1964. The Ecology of Rocky Shores. The English Universities Press Ltd.

Macroalgae and macroalgal detritus have also been shown to be an important food source for benthic organisms, because macroalgae shed old fronds.{{cite journal |last1=Krause-Jensen |first1=Dorte |last2=Duarte |first2=Carlos |title=Substantial role of macroalgae in marine carbon sequestration |journal=Nature Geoscience |date=2016 |volume=9 |issue=10 |pages=737–742 |doi=10.1038/ngeo2790 |bibcode=2016NatGe...9..737K |url=https://www.nature.com/articles/ngeo2790#citeas}}.

These macroalgal fronds tend to be utilized by benthos in the intertidal zone close to the shore.{{cite journal |last1=Dunton |first1=K. H. |last2=Schell |first2=D. M. |title=Dependence of consumers on macroalgal (Laminaria solidungula) carbon in an arctic kelp community: δ13C evidence |journal=Marine Biology |date=1987 |volume=93 |issue=4 |pages=615–625 |doi=10.1007/BF00392799|bibcode=1987MarBi..93..615D |s2cid=84714929 }}{{cite journal |last1=Renaud |first1=Paul E. |last2=Løkken |first2=Therese S. |last3=Jørgensen |first3=Lis L. |last4=Berge |first4=Jørgen |last5=Johnson |first5=Beverly J. |title=Macroalgal detritus and food-web subsidies along an Arctic fjord depth-gradient |journal=Front. Mar. Sci. |date=June 2015 |volume=2 |page=31 |doi=10.3389/fmars.2015.00031 |s2cid=10417856 |doi-access=free |bibcode=2015FrMaS...2...31R }}

Alternatively, pneumatocysts (gas filled "bubbles") can keep the macroalgae thallus afloat; fronds are transported by wind and currents from the coast into the deep ocean. It has been shown that benthic organisms also at several 100 m tend to utilize these macroalgae remnants.

As macroalgae takes up carbon dioxide and releases oxygen in the photosynthesis, macroalgae fronds can also contribute to carbon sequestration in the ocean, when the macroalgal fronds drift offshore into the deep ocean basins and sink to the sea floor without being remineralized by organisms. The importance of this process for blue carbon storage is currently a topic of discussion among scientists.{{cite journal |last1=Watanabe |first1=Kenta |last2=Yoshida |first2=Goro |last3=Hori |first3=Masakazu |last4=Umezawa |first4=Yu |last5=Moki |first5=Hirotada |last6=Kuwae |first6=Tomohiro |title=Macroalgal metabolism and lateral carbon flows can create significant carbon sinks |journal=Biogeosciences |date=May 2020 |volume=17 |issue=9 |pages=2425–2440 |doi=10.5194/bg-17-2425-2020 |bibcode=2020BGeo...17.2425W |url=https://bg.copernicus.org/articles/17/2425/2020/ |access-date=September 21, 2020|doi-access=free }}{{cite journal |last1=Krause-Jensen |first1=Dorte |last2=Lavery |first2=Paul |last3=Serrano |first3=Oscar |last4=Marbà |first4=Núria |last5=Masque |first5=Pere |last6=Duarte |first6=Carlos M. |title=Sequestration of macroalgal carbon: the elephant in the Blue Carbon room |journal= Biology Letters|date=June 2018 |volume=14 |issue=6 |doi=10.1098/rsbl.2018.0236 |pmid=29925564 |pmc=6030603 |url=}}{{cite journal |last1=Ortega |first1=Alejandra |last2=Geraldi |first2=Nathan R. |last3=Alam |first3=Intikhab |last4=Kamau |first4=Allan A. |last5=Acinas |first5=Silvia G |last6=Logares |first6=Ramiro |last7=Gasol |first7=Josep M |last8=Massana |first8=Ramon |last9=Krause-Jensen |first9=Dorte |last10=Duarte |first10=Carlos M |title=Important contribution of macroalgae to oceanic carbon sequestration |journal=Nature Geoscience |date=2019 |volume=12 |issue=9 |pages=748–754 |doi=10.1038/s41561-019-0421-8|bibcode=2019NatGe..12..748O |hdl=10754/656768 |s2cid=199448971 |hdl-access=free }}

=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.{{cite book |editor=Briand, Frederic |title=CIESM Atlas of Exotic Species in the Mediterranean. Volume 4. Macrophytes. |date=2015 |publisher=CIESM, Paris, Monaco |isbn=9789299000342 |pages=364 |url=https://www.researchgate.net/publication/299381362}}

Production

As of 2019, 35,818,961 tonnes were produced, of which 97.38% were produced in Asian countries.[https://www.fao.org/3/cb4579en/cb4579en.pdf Global seaweeds and microalgae production(FAO)]

class="wikitable floatright" style="text-align:right;"

|+ Seaweed production

! Country

! tonns
per year,
cultured and wild

China

|20,351,442

Indonesia

|9,962,900

South Korea

|1,821,475

Philippines

|1,500,326

North Korea

|603,000

Chile

|427,508

Japan

|412,300

Malaysia

|188,110

Norway

|163,197

United Republic of Tanzania

|106,069

= Farming =

Uses

Seaweed has a variety of uses, for which it is farmed{{cite news|title= Seaweed farmers get better prices if united|url= http://www.sunstar.com.ph/static/dav/2008/06/19/bus/seaweed.farmers.get.better.prices.if.united.jica.html|work= Sun.Star|date= 2008-06-19|access-date= 2008-07-16|archive-url= https://web.archive.org/web/20080909013255/http://www.sunstar.com.ph/static/dav/2008/06/19/bus/seaweed.farmers.get.better.prices.if.united.jica.html|archive-date= 2008-09-09|url-status= dead}} or foraged.{{Cite news|url= http://lifeandhealth.guardian.co.uk/guides/freestuff/story/0,,1981372,00.html

|title= Springtime's foraging treats|access-date=2008-07-16|date= 2007-01-06|newspaper= The Guardian|location= London}}

=Food=

Seaweed is consumed across the world, particularly in East Asia, e.g., Japan, China, Korea, Taiwan and Southeast Asia, e.g. Brunei, Singapore, Thailand, Burma, Cambodia, Vietnam, Indonesia, the Philippines, and Malaysia,{{Cite journal|last=Mohammad|first=Salma|date=4 Jan 2020|title=Application of seaweed (Kappaphycus alvarezii) in Malaysian food products|url=https://www.researchgate.net/publication/338254486|journal=International Food Research Journal|volume=26|pages=1677–1687}} as well as in South Africa, Belize, Peru, Chile, the Canadian Maritimes, Scandinavia, South West England,{{cite web |url=https://www.bbc.co.uk/devon/discovering/taste/laver.shtml |title=Devon Family Friendly – Tasty Seaweed Recipe – Honest! |publisher=BBC |date=2005-05-25 |access-date=2012-06-28}} Ireland, Wales, Hawaii and California, and Scotland.

Gim (김, Korea), nori ({{Lang|ja|海苔}}, Japan) and zicai ({{Lang|zh|紫菜}}, China) are sheets of dried Porphyra used in soups, sushi or onigiri (rice balls). Gamet in the Philippines, from dried Pyropia, is also used as a flavoring ingredient for soups, salads and omelettes.{{cite news |last1=Adriano |first1=Leilanie G. |title='Gamet' sushi festival launched |url=https://www.manilatimes.net/2005/12/21/news/regions/gamet-sushi-festival-launched/693918 |access-date=15 August 2021 |work=The Manila Times |date=21 December 2005}} Chondrus crispus ('Irish moss' or carrageenan moss) is used in food additives, along with Kappaphycus and Gigartinoid seaweed. Porphyra is used in Wales to make laverbread (sometimes with oat flour). In northern Belize, seaweed is mixed with milk, nutmeg, cinnamon and vanilla to make "{{lang|es|dulce}}" ("sweet").

Alginate, agar and carrageenan are gelatinous seaweed products collectively known as hydrocolloids or phycocolloids. Hydrocolloids are food additives.Round F. E. 1962 The Biology of the Algae. Edward Arnold Ltd. 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.{{cite journal |doi=10.1016/j.anifeedsci.2015.09.018 |title=Seaweeds for livestock diets: A review |date=2016 |last1=Makkar |first1=Harinder P.S. |last2=Tran |first2=Gilles |last3=Heuzé |first3=Valérie |last4=Giger-Reverdin |first4=Sylvie |last5=Lessire |first5=Michel |last6=Lebas |first6=François |last7=Ankers |first7=Philippe |journal=Animal Feed Science and Technology |volume=212 |pages=1–17 }}{{cite journal |doi=10.1002/jsfa.6681 |title=Characterization of protein, lipid and mineral contents in common Norwegian seaweeds and evaluation of their potential as food and feed |date=2014 |last1=Mæhre |first1=Hanne K. |last2=Malde |first2=Marian K. |last3=Eilertsen |first3=Karl-Erik |last4=Elvevoll |first4=Edel O. |journal=Journal of the Science of Food and Agriculture |volume=94 |issue=15 |pages=3281–3290 |pmid=24700148 |bibcode=2014JSFA...94.3281M }}

They are valued for fish production.Heuzé V., Tran G., Giger-Reverdin S., Lessire M., Lebas F., 2017. Seaweeds (marine macroalgae). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://www.feedipedia.org/node/78 Last updated on May 29, 2017, 16:46 Adding seaweed to livestock feed can substantially reduce methane emissions from cattle,{{cite web |title=Seaweed shown to reduce 99% methane from cattle |url=https://www.irishtimes.com/news/ireland/irish-news/seaweed-shown-to-reduce-99-methane-from-cattle-1.3156975 |access-date=9 April 2018 |website=irishtimes.com}} but only from their feedlot emissions. As of 2021, feedlot emissions account for 11% of overall emissions from cattle. {{Cite magazine |last=Dutkiewicz |first=Jan |title=Want Carbon-Neutral Cows? Algae Isn't the Answer |language=en-US |magazine=Wired |url=https://www.wired.com/story/carbon-neutral-cows-algae/ |access-date=2023-12-30 |issn=1059-1028}}

=Medicine and herbs=

Image:Seaweed 600.jpg|alt=Photo of rocks covered by dried plant matter]]

Image:Seaweed on rocks at Atlantic Ocean.jpg|alt=Photo of a rock jetty covered with seaweed]]

Alginates are used in wound dressings (see alginate dressing), and dental moulds. In microbiology, agar is used as a culture medium. Carrageenans, alginates and agaroses, with other macroalgal polysaccharides, have biomedicine applications. Delisea pulchra may interfere with bacterial colonization.{{cite journal |author1=Francesca Cappitelli |author2=Claudia Sorlini |year=2008 |title=Microorganisms attack synthetic polymers in items representing our cultural heritage |journal=Applied and Environmental Microbiology |volume=74 |issue=3 |pages=564–569 |pmc=2227722 |pmid=18065627 |doi=10.1128/AEM.01768-07|bibcode=2008ApEnM..74..564C }} Sulfated saccharides from red and green algae inhibit some DNA and RNA-enveloped viruses.{{cite journal |author1=Kazłowski B. |author2=Chiu Y. H. |author3=Kazłowska K. |author4=Pan C. L. |author5=Wu C. J. |date=August 2012 |title=Prevention of Japanese encephalitis virus infections by low-degree-polymerisation sulfated saccharides from Gracilaria sp. and Monostroma nitidum |journal=Food Chem. |volume=133 |issue=3 |pages=866–74 |doi=10.1016/j.foodchem.2012.01.106}}

Seaweed extract is used in some diet pills.{{Cite journal|last1=Maeda|first1=Hayato|last2=Hosokawa|first2=Masashi|last3=Sashima|first3=Tokutake|last4=Funayama|first4=Katsura|last5=Miyashita|first5=Kazuo|date=2005-07-01|title=Fucoxanthin from edible seaweed, Undaria pinnatifida, shows antiobesity effect through UCP1 expression in white adipose tissues|journal=Biochemical and Biophysical Research Communications|volume=332|issue=2|pages=392–397|doi=10.1016/j.bbrc.2005.05.002|issn=0006-291X|pmid=15896707}} Other seaweed pills exploit the same effect as gastric banding, expanding in the stomach to make the stomach feel more full.{{cite web |url=https://www.foxnews.com/story/new-seaweed-pill-works-like-gastric-banding |title=New Seaweed Pill Works Like Gastric Banding |website=Fox News|date=25 March 2015 }}{{cite web |url=http://news.softpedia.com/news/Appesat-the-Seaweed-Diet-Pill-that-Expands-in-the-Stomach-101227.shtml |title=Appesat, the Seaweed Diet Pill that Expands in the Stomach |author=Elena Gorgan |date=6 January 2009 |website=softpedia}}

=Climate change mitigation=

{{excerpt|Seaweed farming#Climate change mitigation|paragraphs=1|file=no}}

=Other uses=

Other seaweed may be used as fertilizer, compost for landscaping, or to combat beach erosion through burial in beach dunes.{{cite news |first=Ihosvani |last=Rodriguez |title=Seaweed invading South Florida beaches in large numbers |url=http://www.sun-sentinel.com/news/broward/fort-lauderdale/fl-lauderdale-beach-seaweed-20120410,0,3244366.story |archive-url=https://archive.today/20130203181239/http://www.sun-sentinel.com/news/broward/fort-lauderdale/fl-lauderdale-beach-seaweed-20120410,0,3244366.story |url-status=dead |archive-date=February 3, 2013 |work=South Florida Sun-Sentinel |date=April 11, 2012 |access-date=2012-04-11 }}

Seaweed is under consideration as a potential source of bioethanol.{{cite web|url=http://alotofyada.blogspot.co.uk/2008/06/seaweed-power-ireland-taps-new-energy.html|title=Seaweed Power: Ireland Taps New Energy Source|date=2008-06-24|website=alotofyada.blogspot.co.uk|access-date=9 April 2018}}{{Cite journal|title=Macroalgae for biofuels production: Progress and perspectives|journal=Renewable and Sustainable Energy Reviews|volume=47|pages=427–437|doi=10.1016/j.rser.2015.03.086|year=2015|last1=Chen|first1=Huihui|last2=Zhou|first2=Dong|last3=Luo|first3=Gang|last4=Zhang|first4=Shicheng|last5=Chen|first5=Jianmin}}

File:Harvesting (cleaning) algae that have grown in an algae scrubber.jpg

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).{{Cite web|url=https://www.materialdriven.com/home/2017/6/16/the-promise-of-bioyarn-from-algiknit|title=The promise of Bioyarn from AlgiKnit|website=MaterialDriven}}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}

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.File:Harvesting seaweed in Jambiani.jpg

Seaweed is sometimes used to build roofs on houses on Læsø in Denmark.{{cite web|url=http://naturalhomes.org/seaweed-house.htm|title=Seaweed Thatch|website=naturalhomes.org|access-date=9 April 2018}}

File:Onigiri at an onigiri restaurant by zezebono in Tokyo.jpg|Onigiri and wakame miso soup, Japan

File: Laver and toast.JPG|Laverbread 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 Indonesia, with each rectangle belonging to a different family

Health risks

Rotting seaweed is a potent source of hydrogen sulfide, a highly toxic gas, and has been implicated in some incidents of apparent hydrogen sulfide poisoning.{{cite web|url=http://www.google.com/hostednews/afp/article/ALeqM5hmSXIrejkYYs-g9Y0L71SD9qNl7w?hl=fr|archive-url=https://web.archive.org/web/20140224213157/http://www.google.com/hostednews/afp/article/ALeqM5hmSXIrejkYYs-g9Y0L71SD9qNl7w?hl=fr|url-status=dead|title=Algues vertes: la famille du chauffeur décédé porte plainte contre X|trans-title=Green algae: the family of the deceased driver files a complaint against X|publisher=AFP|via=Google News |location=Saint-Brieuc|date=2010-04-22|archive-date=2014-02-24|access-date=2010-04-22|language=fr}} It can cause vomiting and diarrhea.{{Citation |last=Contaminants |first=National Research Council (US) Committee on Emergency and Continuous Exposure Guidance Levels for Selected Submarine |title=Hydrogen Sulfide |date=2009 |work=Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants: Volume 3 |url=https://www.ncbi.nlm.nih.gov/books/NBK219913/ |access-date=2024-02-10 |publisher=National Academies Press (US) |language=en}}

The so-called "stinging seaweed" Microcoleus lyngbyaceus is a filamentous cyanobacteria which contains toxins including lyngbyatoxin-a and debromoaplysiatoxin. Direct skin contact can cause seaweed dermatitis characterized by painful, burning lesions that last for days.{{cite web|url=https://www.cabdirect.org/cabdirect/abstract/19822902103|url-access=subscription|title=Escharotic stomatitis caused by the "stinging seaweed" Microcoleus lyngbyaceus (formerly Lyngbya majuscula): case report and literature review}}{{cite journal|title=Lyngbya dermatitis (toxic seaweed dermatitis)|journal=International Journal of Dermatology|volume=51|issue=1|pages=59–62|doi=10.1111/j.1365-4632.2011.05042.x|pmid=21790555|year=2012|last1=Werner|first1=K. A.|last2=Marquart|first2=L.|last3=Norton|first3=S. A.|s2cid=22375739}}

Threats

Bacterial disease ice-ice infects Kappaphycus (red seaweed), turning its branches white. The disease caused heavy crop losses in the Philippines, Tanzania and Mozambique.{{Cite web |last=Buck |first=Holly Jean |date=April 23, 2019 |title=The desperate race to cool the ocean before it's too late |url=https://www.technologyreview.com/s/613327/the-desperate-race-to-cool-the-ocean-before-its-too-late/ |access-date=2019-04-28 |website=MIT Technology Review |language=en-US}}

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

[https://www.seaweed.ie/ Michael Guiry's Seaweed Site] information on all aspects of algae, seaweed and marine algal biology
[https://web.archive.org/web/20110514190554/http://www.seaweedafrica.org/ SeaweedAfrica], information on seaweed utilisation for the African continent.
[http://histoires-de-sciences.over-blog.fr/2017/08/seaweed.a-chemical-industry-in-brittany-in-the-past-and-today.html Seaweed. A chemical industry in Brittany, in the past and today.]
[https://www.algaebase.org/ AlgaeBase], a searchable taxonomic, image, and utilization database of freshwater, marine and terrestrial algae, including seaweed.

Category:Blue carbon

Category:Edible algae

Category:Polyphyletic groups

Weed