Sea-king Kelp: How Seaweed Farming Could Save the World

Seaweed is a common object in the context of our coastlines, but the potential that it holds is far from ordinary. This article will explore what seaweed is, how it is connected to cultures other than our own, and the security that seaweed aquaculture can offer in the face of a global biodiversity crisis.

It is a common misconception that seaweeds are plants. Seaweeds are actually marine algae. There are thousands of different seaweed species, but they can be split into three official groups. These are green algae, red algae and brown algae:

• Green algae (Chlorophyta): There are around 4,000 known species of green algae, and they exist in three different forms; unicellular, colonial or multicellular. The green pigmentation of this algae is due to chlorophyll, thus thrives in higher light intensity environments. This is a very adaptable algae, as it can be found in both freshwater and saltwater environments.

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• Red algae (Rhodophyta): There are around 6,000 known species of red algae, which can be identified by their distinctive red colour, which is created by the pigment phycoerythrin. This pigment is effective at absorbing blue light, which allows red algae to thrive at greater and darker depths of the ocean than its brown and green counterparts.

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• Brown algae (Phaeophyta): There are only 2,000 known species of brown algae, but it is the most prevalent. It is very adaptable, existing in both temperate and arctic climates, and found in both freshwater and saltwater environments. The brown/yellow colour of brown algae varies across species due to the proportions of its brown pigments (fucoxanthin) and chlorophyll pigments.

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Seaweeds are a crucial component of ocean ecology because they provide shelter and develop into habitats for marine organisms such as the sea urchin. For example, vast areas of kelp (a type of brown algae) are crucial cover for juvenile species and support huge populations and demographics of marine creatures. They are also vital in oxygenating the ocean as a byproduct of photosynthesis – it is thought that seaweed is responsible for oxygenating over half of Earth.

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Aquaculture is the farming of marine organisms. There has been a surge of aquaculture investments in recent years (E.g. Russia, who have invested EUR 20 billion) to ensure abundant and consistent fish/crustacean yields, to counteract the drop in stocks caused by overfishing and trawling. But aquaculture is not limited to the fishing sector, it can also be used to cultivate masses of seaweed.Seaweed is used in a variety of ways; it is often used as a vitamin-rich food item, but it can also be used in cosmetics and medicines, reinvented as plastic-free alternative textiles, and any waste can be used as animal feed after fermentation.

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However, seaweed aquaculture is not a new concept, nor a Western invention. Japanese culture and seaweed aquaculture have been heavily connected for centuries, and it estimated that the country eats around 9 billion seaweed blades every year. A Northern region of the island nation named Sankriku cultivates seaweed using a method that involves ‘seed strings’. The strings germinate over the summer months, and are then put into the ocean in autumn when the sea temperature begins to decline. Once the algal sporophytes (blades) have reached 2 metres long they are harvested, trimmed, blanched in seawater, cooled and then preserved in salt-water solution, drained, dehydrated, quality checked and then packed. As well as being a food item itself, seaweed attracts other sought after stocks such as sea urchins. Due to the length of time that seaweed aquaculture has existed within Japan, it is clear that the process is a sustainable and holistic practice with both economic and environmental benefits.

It is well known that terrestrial agriculture has had catastrophic impacts on the landscape and biodiversity. This is because of the resulting deforestation, chemical run-off, greenhouse gas emissions and soil erosion that occurs alongside the agricultural process. Seaweed is an independent crop that requires little-to-no intervention in its production process, and it has been well studied that it aids marine environments due to its ability to protect juvenile biodiversity and improve water quality through oxygenation. There has even been studies into how seaweed can act as a buffer against ocean acidification. Perhaps if investments in aquaculture continue, terrestrial landscapes could be relieved from some pressures of agricultural demand and could begin to recover.

Where to find out more:

• The types of seaweed: https://www.thoughtco.com/types-of-marine-algae-2291975
• Seaweed habitation: https://www.msc.org/what-you-can-do/eat-sustainable-seafood/fish-to-eat/seaweed
• Seaweed oxygenation: https://oceanservice.noaa.gov/facts/ocean-oxygen.html
• Seaweed aquaculture: https://www.aquaculturealliance.org/blog/seaweed-aquaculture-benefits/
• The uses of seaweed: https://www.bbc.co.uk/news/business-53610683
• Japanese culture and seaweed: https://thefishsite.com/articles/big-in-japan-but-can-seaweed-conquer-the-rest-of-the-world-too
• Seaweed buffer against ocean acidification: https://iopscience.iop.org/article/10.1088/1748-9326/11/3/034023/meta