Seaweed farming is the practice of growing and harvesting seaweed . In its simplest form, it consists of the management of naturally found batches. In its most advanced form, it consists of fully controlling the life cycle of the algae. The main food species grown by aquaculture in Japan, China and Korea include Gelidium , Pterocladia ,  Porphyra , and Laminaria . Seaweed farming has been developed as an alternative to improve economic conditions and to reduce fishing pressure and over exploited fisheries. Seaweeds have been harvested throughout the world as a food source and export product for production of agar and carrageenan products. 
Cultivation of gim (washing) in Korea is reported in the books of 15th century, such as Revised and Augmented Survey of the Geography of Korea and Geography of Gyeongsang Province .  
Seaweed farming started in Japan as early as 1670 in Tokyo Bay .  In autumn of each year, farmers would throw bamboo branches into shallow, muddy water, where the spores of the seaweed would collect. A few weeks later these branches would be moved to a river estuary . The nutrients from the river would help the seaweed to grow. 
In the 1940s, the Japanese improved this method by placing a net of synthetic materials tied to bamboo poles. This effectively doubled the production.  A cheaper variant of this method is called the method hibi – simple ropes stretched between bamboo poles.
In the early 1970s there was a recognized demand for seaweed and seaweed products, outstripping supply, and cultivation. 
The earliest seaweed farming guides in the Philippines recommended cultivation of Laminaria seaweed and reef flats at approximately one meter depth at low tide. They also recommended cutting off sea grasses and removing sea urchins prior to farm construction. Seedlings are then tied to monofilament lines and strung between mangrove stakes pounded into the substrate. This off-bottom method is still one of the major methods used today. 
There are new long-line cultivation methods that can be used in deeper water approximately 7 meters in depth. They use floating cultivation lines in the North Sulawesi , Indonesia .  
Cultivation of seaweed in Asia is a relatively low-tech business with a high labor requirement. There have been many attempts to reduce cultivation, but they have yet to attain commercial viability. 
Environmental and ecological impacts
Several environmental problems can result from seaweed farming. Sometimes seaweed farmers cut down mangroves to use as stakes for their ropes. This, however, negatively affects the farming and reduces the quality of mangrove biodiversity due to depletion. Farmers may also remove eelgrass from their farming areas. This, however, is also discouraged, as it adversely affects water quality. 
Seaweed farming helps to preserve coral reefs,  by increasing diversity where the algae and seaweed have been introduced. Farming may be beneficial by increasing the production of herbivorous fishes and shellfish in the area.  Pollnac & et al 1997b Reported year Increase in population Siginid partner after the start of extensive farming of eucheuma seaweed in villages in North Sulawesi, Indonesia. 
Seaweed culture can also be used to capture, absorb, and add excessive nutrients to living tissue. “Nutrient bioextraction” is the preferred term for bioremediation involving cultured plants and animals. Nutrient bioextraction (also called bioharvesting) is the practice of farming and harvesting shellfish and seaweed for the purpose of removing nitrogen and other nutrients from natural water bodies.  (See main article Nutrient pollution .)
Seaweed farming can be an actor in biological carbon sequestration .
The practice of seaweed farming has long since spread beyond Japan. In 1997 it was estimated that 40,000 people in the Philippines made their living through seaweed farming. Cultivation is also common in all of Asia, Canada, Great Britain, Spain, and the United States. 
In Japan alone annual output value of nori water equivalent to US $ 2 trillion and is one of the world’s Most Valuable crops produced by aquaculture. The high demand in seaweed production provides opportunities and work for the local community. In the Philippines, it has been reported that agricultural land use has grown to a minimum of 5% to 6% of the average wage of an agricultural worker. In the same study they also saw an increase in seaweed exports from 675 metric tons (MT) in 1967 to 13,191 MT in 1980, which doubled to 28,000 MT by 1988. 
- Aquaculture of giant kelp
- Edible seaweed
- Seaweed cultivator
- ^ Jump up to:a b Borgese 1980 , p. 111.
- ^ Jump up to:a b c d Borgese 1980 , p. 112.
- Jump up^ Borgese 1980, p. 116.
- ^ Jump up to:a b Ask 1999 , p. 52.
- Jump up^ Yi, Haeng (1530) . Sinjeung Dongguk Yeoji Seungnam 신증 동국여지승람 (新增 東 國 輿 地 勝 覽)[ Revised and Augmented Survey of the Geography of Korea ] (in Literary Chinese ). Joseon Korea.
- Jump up^ Ha, Yeon; Geum, Yu; Gim, Bin (1425). Gyeongsang-do Jiriji 경상도 지리지 (慶 尙 道 地理 志)[ Geography of Gyeongsang Province ] (in Korean). Joseon Korea.
- Jump up^ Naylor 1967, p. 73.
- ^ Jump up to:a b Crawford 2002 , p. 2.
- Jump up^ Pollnac & et al 1997a, p. 67.
- ^ Jump up to:a b Pollnac & et al 1997b , p. 79.
- Jump up^ Zertruche-Gonzalez 1997, p. 53.
- ^ Jump up to:a b Zertruche-Gonzalez 1997 , p. 54.
- Jump up^ NOAA. “Nutrient Bioextraction Overview” . Long Island Sound Study.
- Jump up^ Trono 1990, p. 4.