Seaweed

Food

Seaweed is consumed by coastal people, particularly in East Asia, e.g. Japan, China, Korea, Taiwan, and Southeast Asia, e.g. Brunei, Singapore, Thailand, Burma, Cambodia, Vietnam, Indonesia, Philippines, and Malaysia, and also in South Africa, Belize, Peru, Chile, the Canadian Maritimes, Scandinavia, South West England,^[9] Ireland, Wales, California, and Scotland.

In Asia, Gim (Korean food) (김, Korea), nori (海苔, Japan), zicai (紫菜, China) are sheets of dried Porphyra used in soups, sushi wrap or onigiri (rice balls). Chondrus crispus (commonly known as 'Irish moss' or carrageenan moss) is another red alga used in producing food additives, along with Kappaphycus and gigartinoid seaweed. Porphyra is a red alga used in Wales to make laver. Laverbread, made from oats and the laver, is a popular dish there. In northern Belize, edible seaweed are mixed with milk, nutmeg, cinnamon, and vanilla to make a common beverage affectionately called "dulce" (or "sweet").

Seaweed are also harvested or cultivated for the extraction of alginate, agar and carrageenan, gelatinous substances collectively known as hydrocolloids or phycocolloids. Hydrocolloids have attained commercial significance as food additives.^[10] 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 products, dairy items and baked goods.

The development of seaweed as an alternative and sustainable source of food and animal feed ingredients depends on the sustainability of the natural resource of raw biomass and on moving the process of feed development from laboratory to industrial scale.^[3]

Herbalism

Seaweed-covered rocks in the United Kingdom

Seaweed on rocks in Long Island

Alginates are commonly used in wound dressings (see alginate dressing), and production of dental moulds. In microbiology research, agar — a plant-based jelly similar to gelatin and made from seaweed — is extensively used as culture medium. Carrageenans, alginates and agaroses (the latter are prepared from agar by purification), with other lesser-known macroalgal polysaccharides, have several important biological activities or applications in biomedicine.

Seaweed extract is used in some diet pills.^{[11] [12]}Other seaweed pills exploit the same effect as gastric banding, expanding in the stomach to make the body feel more full.^[13][14]

Filtration

The strong photosynthesis of algae creates a large affinity for nutrients; this allows the seaweed to be used purposely to remove undesired nutrients from water. Nutrients such as ammonia, ammonium nitrate, nitrite, phosphate, iron, copper, as well as CO₂ are rapidly consumed by growing seaweed. Reefs and lakes are naturally filtered this way (the seaweed being consumed by fish and invertebrates), and this filtering process is duplicated in artificial seaweed filters such as algae scrubbers.

Modern floating algae scrubber/cultivator on a reef pond

Seaweed (macroalgae), as opposed to phytoplankton (microalgae), is used almost universally for filtration purposes because of the need to be able to easily remove (harvest) the algae from the water, which then removes the nutrients. Microalgae require more processing to separate it from the water than macroalgae does; macroalgae is simply pulled out.

When used for filtration, saltwater algae commonly grows species of Cladophora, Ulva (sea lettuce), and Chaetomorpha. Freshwater filtration applications are useful, too, and will commonly grow species such as Spirogyra.

Other uses

Other seaweed may be used as fertilizer, compost for landscaping, or a means of combating beach erosion through burial in beach dunes.^[15] Seaweed is under consideration as a potential source of bioethanol.^[16][17]

Seaweed is lifted out of top of algae scrubber/cultivator, to be discarded or used as food, fertilizer, or skin care

Seaweed is an ingredient in toothpaste, cosmetics and paints.^[6] Alginates enjoy many of the same uses as carrageenan and 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. Research suggests that the Australian seaweed Delisea pulchra may interfere with bacterial colonization.^[18] Sulfated saccharides from both red and green algae have been known to inhibit some DNA and RNA enveloped viruses.^[4]

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.

Women in Tanzania grow "Mwani" (seaweed in Swahili). The farms are made up of little sticks in neat rows in the warm, shallow water. Once they harvest the seaweed, it is used for many purpose: food, cosmetics, fabric, etc.

Seaweed is sometimes used to build roofs on houses on Læsø in Denmark ^[19]

Seaweeds are also used as animal feeds. They have long been grazed by sheep, horses and cattle in Northern Europe. They are currently particularly valuable for fish production.^[20] Adding seaweed to livestock feed can substantially reduce methane emissions from cattle.^[21]