Seaweed farming

Seaweed farmingorkelpfarmingis the practice ofcultivatingandharvestingseaweed. In its simplest form farmers gather from natural beds, while at the other extreme farmers fully control the crop'slife cycle.
The seven most cultivatedtaxaareEucheumaspp.,Kappaphycus alvarezii,Gracilariaspp.,Saccharina japonica,Undaria pinnatifida,Pyropiaspp., andSargassum fusiforme.EucheumaandK. alvareziiare attractive forcarrageenan(agelling agent);Gracilariais farmed foragar; the rest are eaten after limited processing.Seaweeds are different frommangrovesandseagrasses, as they are photosynthetic algal organismsand are non-flowering.
The largest seaweed-producing countries as of 2022 areChina(58.62%) andIndonesia(28.6%); followed bySouth Korea(5.09%) and thePhilippines(4.19%). Other notable producers includeNorth Korea(1.6%),Japan(1.15%),Malaysia(0.53%),Zanzibar(Tanzania, 0.5%), andChile(0.3%).Seaweed farming has frequently been developed to improve economic conditions and to reduce fishing pressure.
TheFood and Agriculture Organization(FAO) reported that world production in 2019 was over 35 million tonnes. North America produced some 23,000 tonnes of wet seaweed. Alaska, Maine, France, and Norway each more than doubled their seaweed production since 2018.As of 2019, seaweed represented 30% of marineaquaculture.In 2023, the global seaweed extract market was valued at $16.5 billion, with strong projected growth.
Seaweed farming is acarbon negativecrop, with a high potential forclimate change mitigation.The IPCCSpecial Report on the Ocean and Cryosphere in a Changing Climaterecommends "further research attention" as a mitigation tactic.World Wildlife Fund, Oceans 2050, andThe Nature Conservancypublicly support expanded seaweed cultivation.
The earliest seaweed farming guides in the Philippines recommended the cultivation ofLaminariaseaweed and reef flats at approximately one meter's depth at low tide. They also recommended cutting off seagrasses and removing sea urchins before farm construction. Seedlings are tied to monofilament lines and strung between mangrove stakes in the substrate. This off-bottom method remains a primary method.
Long-line cultivation methods can be used in water approximately 7 meters (23 ft) in depth. Floating cultivation lines are anchored to the bottom and are widely used inNorth Sulawesi,Indonesia.Species cultured by long-line include those of the generaSaccharina,Undaria,Eucheuma,Kappaphycus, andGracilaria.
Cultivation in Asia is relatively low-technology with a high labor requirement. Attempts to introduce technology to cultivate detached plant growth in tanks on land to reduce labor have yet to attain commercial viability.
A bacterial infection calledice-icestunts seaweed crops. In the Philippines 15 percent reduction in one species appeared in 2011 to 2013, representing 268,000 tonnes of seaweed.The spread of ice-ice disease is strongly associated with increasing seawater temperatures.
Seaweed is an extractive crop that has little need for fertilisers or water, meaning that seaweed farms typically have a smaller environmental footprint than other agriculture or fedaquaculture.Many of the impacts of seaweed farms, both positive and negative, remain understudied and uncertain.
Nonetheless, many environmental problems can result from seaweed farming.For instance, seaweed farmers sometimes cut downmangrovesto use as stakes. Removing mangroves negatively affects farming by reducing water quality and mangrove biodiversity. Farmers may removeeelgrassfrom their farming areas, damaging water quality.
Seaweed farming can pose a biosecurity risk, as farming activities have the potential to introduce or facilitateinvasive species.For this reason, regions such as the UK, Maine and British Columbia only allow native varieties.
Farms may also have positive environmental effects. They may support welcomeecosystem servicessuch asnutrient cycling, carbon uptake, and habitat provision.
Evidence suggests that seaweed farming can have positive impacts which include supplementing human diets, feeding livestock, creating biofuels, slowing climate change and providing crucial habitat for a marine life, but must scale sustainably in order to have these effects.One way for seaweed farming to scale at terrestrial farming levels is with the use ofROVs, which can install low-cost helical anchors that can extend seaweed farming into unprotected waters.
Seaweed can be used to capture, absorb, and incorporate excess nutrients into living tissue, aka nutrient bioextraction/bioharvesting, is the practice offarming and harvesting shellfish and seaweed to remove nitrogen and other nutrients from natural water bodies.
Similarly, seaweed farms may offer habitat that enhancesbiodiversity.Seaweed farms have been proposed to protect coral reefsby increasing diversity, providing habitat for local marine species. Farming may increase the production of herbivorous fish and shellfish.Pollinac reported an increase inSiginidpopulation after the start of farming ofEucheumaseaweed in villages in North Sulawesi.
In Japan the annual production ofnoriamounts to US$2 billion and is one of the world's most valuable aquaculture crops. The demand for seaweed production provides plentiful work opportunities.
A study conducted by the Philippines reported that plots of approximately onehectarecould produce net income fromEucheumafarming was 5 to 6 times the average wage of an agriculture worker. The study also reported an increase in seaweed exports from 675 metric tons (MT) in 1967 to 13,191 MT in 1980, and 28,000 MT by 1988.
About 0.7 million tonnes of carbon are removed from the sea each year by commercially harvested seaweeds.In Indonesia, seaweed farms account for 40 percent of the national fisheries output and employ about one million people.
The Safe Seaweed Coalition is a research and industry group that promotes seaweed cultivation.
Seaweed farming has had widespread socio-economic impacts in Tanzania, has become a very important source of resources for women, and is the third biggest contributor of foreign currency to the country.90% of the farmers are women, and much of it is used by the skincare and cosmetics industry.
In 1982Adelaida K. Semesibegan a programme of research into seaweed cultivation inZanzibarand its application resulted in greater investment in the industry.
Farmed seaweed is used in industrial products, as food, as an ingredient in animal feed, and as source material forbiofuels.
Seaweeds are used to produce chemicals that can be used for various industrial, pharmaceutical, or food products. Two major derivative products arecarrageenanandagar. Bioactive ingredients can be used for industries such aspharmaceuticals,industrial food,andcosmetics.
Seaweed cultivation in the open ocean can act as a form of carbon sequestration to mitigate climate change.Studies have reported that nearshore seaweed forests constitute a source ofblue carbon, as seaweed detritus is carried into the middle and deep ocean thereby sequestering carbon.Macrocystis pyrifera(also known as giant kelp) sequesters carbon faster than any other species. It can reach 60 m (200 ft) in length and grow as rapidly as 50 cm (20 in) a day.According to one study, covering 9% of the world's oceans with kelp forests could produce "sufficientbiomethaneto replace all of today's needs in fossil fuel energy, while removing 53 billion tons of CO2per year from the atmosphere, restoring pre-industrial levels".
Seaweed farming may be an initial step towards adapting to andmitigatingclimate change. These include shoreline protection through the dissipation of wave energy, which is especially important to mangrove shorelines. Carbon dioxide intake would raisepHlocally, benefitting calcifiers (e.g. crustaceans) or in reducing coral bleaching. Finally, seaweed farming could provide oxygen input to coastal waters, thus counteringocean deoxygenationdriven by risingocean temperature.
Tim Flanneryclaimed that growing seaweeds in the open ocean, facilitated by artificial upwelling and substrate, can enable carbon sequestration if seaweeds are sunk to depths greater than one kilometer.
Seaweed contributes approximately 16–18.7% of the total marine-vegetation sink. In 2010 there were 19.2 ×106{\displaystyle 10^{6}}tons of aquatic plants worldwide, 6.8 ×106{\displaystyle 10^{6}}tons forbrown seaweeds; 9.0 ×106{\displaystyle 10^{6}}tons for red seaweeds; 0.2 ×106{\displaystyle 10^{6}}tons of green seaweeds; and 3.2 ×106{\displaystyle 10^{6}}tons of miscellaneous aquatic plants. Seaweed is largely transported from coastal areas to the open and deep ocean, acting as a permanent storage of carbon biomass within marine sediments.
Ocean afforestation is a proposal for farming seaweed forcarbon removal.After harvesting seaweed is decomposed intobiogas(60%methaneand 40%carbon dioxide) in ananaerobic digester. The methane can be used as a biofuel, while the carbon dioxide can be stored to keep it from the atmosphere.
Similarly, the NGO Climate Foundation andpermacultureexperts claimed that offshore seaweed ecosystems can be cultivated according to permaculture principles, constitutingmarine permaculture.The concept envisions using artificial upwelling and floating, submerged platforms as substrate to replicate natural seaweed ecosystems that provide habitat and the basis of a trophic pyramid for marine life.Seaweeds and fish can be sustainably harvested. As of 2020, successful trials had taken place in Hawaii, the Philippines, Puerto Rico and Tasmania.The idea featured as a solution covered by the documentary2040and in the bookDrawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming.
Human use of seaweed is known from theNeolithic period.Cultivation ofgim(laver) inKoreais reported in books from the 15th century.Seaweed farming began in Japan as early as 1670 inTokyo Bay.In autumn of each year, farmers would throwbamboobranches into shallow, muddy water, where the spores of the seaweed would collect. A few weeks later these branches would be moved to a riverestuary. Nutrients from the river helped the seaweed to grow.
In the 1940s, the Japanese improved this method by placing nets of synthetic material tied to bamboo poles. This effectively doubled production.A cheaper variant of this method is called thehibimethod—ropes stretched between bamboo poles. In the early 1970s, demand for seaweed and seaweed products outstripped supply, and cultivation was viewed as the best means to increase production.
In the tropics, commercial cultivation ofCaulerpa lentillifera(sea grapes) was pioneered in the 1950s inCebu, Philippines, after accidental introduction ofC. lentilliferato fish ponds on the island ofMactan.This was further developed by local research, particularly through the efforts ofGavino Trono, since recognized as aNational Scientist of the Philippines. Local research and experimental cultures led to the development of the first commercial farming methods for other warm-water algae (since cold-water red and brown edible algae favored inEast Asiado not grow in the tropics), including the first successful commercial cultivation ofcarrageenan-producing algae. These includeEucheumaspp.,Kappaphycus alvarezii,Gracilariaspp., andHalymeniadurvillei.In 1997, it was estimated that 40,000 people in thePhilippinesmade their living through seaweed farming.The Philippines was the world's largest producer of carrageenan for several decades until it was overtaken byIndonesiain 2008.
Seaweed farming spread beyond Japan and the Philippines to southeast Asia, Canada, Great Britain, Spain, and the United States.
In the 2000s, seaweed farming has been getting increasing attention due to its potential formitigating both climate changeand other environmental issues, such asagricultural runoff.Seaweed farming can be mixed with otheraquaculture, such as shellfish, to improve water bodies, such as in the practices developed by American non-profitGreenWave.The IPCCSpecial Report on the Ocean and Cryosphere in a Changing Climaterecommends "further research attention" as a mitigation tactic.
In 2024 a commercial-scale seaweed farm began construction within the Hollandse Kust Zuid (HKZ) 139 turbine wind farm. The project uses 13-metre long "Eco-anchors" that cover the surface with a marine life habitat using materials such as oyster shells, wood, and cork.
This article incorporates text from afree contentwork. Licensed under CC BY-SA 3.0 IGO (license statement/permission). Text taken fromIn brief, The State of World Fisheries and Aquaculture, 2018​, FAO, FAO.