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The many ways in which seaweed can save the environment

The many ways in which seaweed can save the environment

| Text: Fayme Alm, Foto: Christian Bille Jendresen

In Denmark, researchers, companies, authorities and interest organisations have come together in Tang Nu (Danish for Seaweed Now), a project exploring how seaweed farming might help create cleaner oceans and how to use seaweed biomass as food and animal feed.

“We like to say that seaweed is like a Kinder Surprise. It has so many possible solutions and challenges and can be used as a bioresource, food, animal feed, material and medicine. Seaweed absorbs both nutrition and CO2 and can clearly improve the environment,” Annette Bruhn, a marine biologist and senior researcher at Aarhus University, tells the Nordic Labour Journal.

Anette Bruhn

When asked how seaweed can help mitigate the climate crisis, the Danish researcher provides the following examples:

  • One tonne of farmed and dried seaweed binds at least one to two tonnes of CO2 using photosynthesis. 
  • If we replace imported soya with locally produced seaweed as animal feed, we cut CO2 emissions from transport.
  • More than 40% of the world’s methane emissions come from cows. If we mix certain types of seaweed in their feed, the methane emissions fall by up to 98%. 
  • Seaweed’s ability to absorb CO2 also helps reducing local ocean acidity.
  • As a foodstuff, seaweed is also a good source of carbohydrates, proteins and fat. 

“Seaweed contains no more than 1 to 3% fat, but this is the good type of fat which is rich in omega-3,” says Annette Bruhn.

The elements and the necessary balance  

So what about elements like arsenic, iron, iodine and zinc, which are also found in seaweed? Can a seaweed eater digest too much of these elements?

“We humans need a certain amount of these elements, but we must always keep a balance and regulate the amounts that we eat in order not to get too much of any one thing. There are also variations in the amount of different elements depending on where the seaweed is being farmed, and during which time of year,” says Annette Bruhn.

The many qualities of seaweed

If seaweed disappeared, what would happen?

“It would have an impact on the climate because seaweed absorbs large amounts of CO2 from the atmosphere and turns it into marine resources in the oceans. Biodiversity would also suffer since seaweed is both food and home for small and large animals and other ocean plants. 

"The food chain would be affected since the small animals eat seafood and the larger animals eat the smaller ones. Even commercially fished species like cod live in seaweed when they are small, so if it disappeared the number of cod would be hit.”  

How do we protect the seaweed?

“By reducing nutrient pollution which makes fast-growing species grow faster because of too many nutrients, and they wipe out species that grow slowly and contribute to more biodiversity.”

The Nordic blue forests

Blue Carbon – climate adaptation, CO2 uptake and sequestration of carbon in Nordic blue forests” is a newly published report from the Nordic Council of Ministers. With blue carbon, they mean carbon captured by living organisms in coastal vegetated ecosystems and stored in biomass and sediments. 

The Danish, Finnish and Norwegian researchers behind the report have studied these three types of Nordic wild blue forests: 

  1. Kelp forests – large brown algae growing on rocks or hard sediment in permanently water-covered areas.
  2. Seaweed in tidal zones – brown algae growing on rocks that are sometimes covered in water and sometimes exposed.
  3. Seagrass meadows – marine plants making up subsea meadows on soft sediment.

The project’s main focus has been the blue forests’ ability to help the ocean’s ability to sequester carbon. While these marine forests are growing, they gather carbon and nutrients in their biomass. Parts of this biomass then end up in carbon sink deposits on the seabed and help cut carbon emissions.

The first Nordic seaweed map

The report’s results include the mapping of what effect climate change and other human-caused changes have on the ecosystems of the Nordics’ blue forests.

Seaweed map

Dorte Krause-Jensen, Professor of marine biodiversity and ecology at Aarhus University, is one of the researchers behind the report. She tells the Nordic Labour Journal that the map is an important tool for monitoring the seaweed stocks.

“The blue forests are growing partly hidden under the surface. To manage them in an efficient way you need to know where to find them.” 

Seaweed needs resilience

The report also gives general advice for the management of the Nordics’ blue forests, which is particularly important as some of them have already been lost. 

“We encourage targeted measures to protect them from factors like eutrophication, overfishing and habitat fragmentation. It might also be necessary to repair and recreate lost habitats to help speed up the re-establishment,” says Dorte Krause-Jensen.  

Loss of habitat can be due to too frequent harvesting which risks ruining the seaweed.  

“In some countries, large amounts of wild seaweed are being harvested. In these places, it would be good to stop the harvest or at least make it sustainable. Another alternative is to farm the seaweed you will use and protect seaweed forests that are now being harvested far too frequently,” says Annette Bruhn.

Eelgrass an important part of the blue forests

Eelgrass is important for CO2 uptake, but it can also be used to produce zosteric acid. This is a medication used in osteopathic medicine. It is also used in ship paint to prevent the growth of algae on the hull.


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