Seaweed Farming

Seaweed farming or kelp farming is the practice of cultivating 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 top seven most cultivated seaweed taxa are ''Eucheuma'' spp., ''Kappaphycus alvarezii'', ''Gracilaria'' spp., ''Saccharina japonica'', '' Undaria pinnatifida'', ''Pyropia'' spp., and '' Sargassum fusiforme''. ''Eucheuma'' and ''K. alvarezii'' are farmed for carrageenan (a gelling agent); ''Gracilaria'' is farmed for agar; while the rest are farmed for food. The largest seaweed-producing countries are China, Indonesia, and the Philippines. Other notable producers include South Korea, North Korea, Japan, Malaysia, and Zanzibar (Tanzania). Seaweed farming has frequently been developed as an alternative to improve economic conditions and to reduce fishing pressure and overexploited fisheries.

Global production of farmed aquatic plants, overwhelmingly dominated by seaweeds, grew in output volume from in 1995 to just over in 2016. As of 2014, seaweed was 27% of all marine aquaculture.

Seaweed farming is a carbon negative crop, with a high potential for climate change mitigation. The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate recommends "further research attention" as a mitigation tactic.

Methods

The earliest seaweed farming guides in the Philippines recommended the cultivation of ''Laminaria'' seaweed 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 then tied to monofilament lines and strung between mangrove stakes pounded into the substrate. This off-bottom method is still one of the primary 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 anchored to the bottom and are the primary methods used in the villages of North Sulawesi, Indonesia. Species cultured by long-line include those of the genera ''Saccharina'', '' Undaria'', ''Eucheuma'', ''Kappaphycus'', and ''Gracilaria.''

The cultivation of seaweed in Asia is a relatively low-technology business with a high labor requirement. There have been many attempts in various countries to introduce high technology to cultivate detached plant growth in tanks on land to reduce labor, but they have yet to attain commercial viability.

Environmental and ecological impacts

Seaweed is an extractive crop that has little need for fertilisers or water, meaning that seaweed farms typically have a limited environmental footprint compared to other forms of agriculture or fed aquaculture. Nonetheless, many environmental problems can result from seaweed farming. For instance, seaweed farmers sometimes cut down mangroves to use as stakes for their ropes. This, however, negatively affects farming since it reduces the water quality and mangrove biodiversity due to depletion. Farmers may also sometimes remove eelgrass