Seaweed farming began 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 nets of synthetic material tied to bamboo poles. This effectively doubled the production. A cheaper variant of this method is called the hibi method: simple ropes stretched between bamboo poles.
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 since it reduces the water quality. Farmers may also sometimes remove eelgrass from their farming areas. This however is also discouraged as it negatively affects water quality.
Seaweed farming helps to preserve coral reefs.
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 Southeast Asia, Canada, Great Britain, Spain, and the United States.
We have this available on https://seatechbioproducts.com/marine-algae-micro-and-macro-seaweeds
Principles of Aquaculture and fish farming in including other species such as algae, oyster, seaweed and more- Edited by laura Vermon from high quality Wikipedia Articles (page 102-103)