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Urban farming underwater: Growing mussels and seaweed for a cleaner and more diverse harbour in Copenhagen

By Beata Wallsten and Sandra Kaarsgaard, Monday March 22nd 2021

Mussels and seaweed is one way to go for a cleaner Copenhagen harbour. On Kalvebod Bølge, or Kalvebod Wave, on the Danish capital’s waterfront, the organization Havhøst is cultivating life under water.

A 'sock' on the promenade
It is springtime in Copenhagen, the time when the mussels reproduce. Havhøst starts the process of cultivating the mussels during these months.
Photo: Sandra Kaarsgaard

The mussels eat the nutrition and the algae in the water and become mussels which we could eat. That is why it is regenerative.

Kathrine Strange, student worker from Havhøst.
Kathrine Strange behind hovered 'socks'  at the wave field
“The way that the mussels clean the water is that they are filtered eaters, they filter the water around them. That is how they live”, says Kathrine Strange. Photo: Sandra Kaarsgaard

Unlike mussels, the seaweed does not clean the water, but it uses nutrition to grow and then becomes an edible leaf.

By removing nutrients from the water like this, growing seaweed helps the ocean, she continues.

We have too much algae and nutrition in the water which makes it unhealthy. The nutrition is coming from farming.

says Kathrine Strange
Infographic on the process of growing mussels in 'socks' in the wave field
Infographic: Beata Wallsten

The water in the Copenhagen harbor is at the moment clean enough for swimming, but not necessarily for eating the mussels. Kathrine Strange thinks this could be possible in the future.

She adds that more initiatives like this are needed for a cleaner harbour. As well as for strengthening the Danes’ relationship to the water which they are surrounded by.

We can eat and harvest the ocean in a sustainable way. Then we can get this better world and ocean and strengthen our love for it.

Kathrine Strange
Mussels on Havhøsts wave field

The Copenhagen harbor is clean compared to other capitals, but the water is still affected by the surroundings. More extreme weather with greater rainfalls makes sewage pollute the ocean, and boat traffic and nutrition from farming gets to the Copenhagen water. Photos: Sandra Kaarsgaard

Mussels growing on a metal pillar

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