Sugar kelp being moved into the sea

Work on putting out this year’s crop of kelp has begun. Finally, the water is cold enough for the other organisms that grew on the sugar kelp, and which represent a threat to it, to be less dominant.

“Kelp prefers cold water, and naturally it grows from autumn until spring. By mid-June it begins to break down, due to excessively high water temperatures and algal blooms”, says Ocean Forest’s production manager for kelp cuttings, Sunniva Tangen Haldorsen.

This is what it looks like at sea after the carrying line has been set out.

This fall, between 7.5 and 8.5 km of rope with sugar kelp will be put into the sea each week. Transferring the kelp requires resources, staff and equipment, which is why it takes over two months. The exact amount that is put into the water each week will vary, depending on the weather, but in total it will be between 60 and 70 km of rope.

Easy to grow

The sea north of Austevoll is where the sugar kelp will grow big. Once it has been put out, you can just about spot the ropes with sugar kelp, if you are close enough: the ropes are only half a metre below the surface. Here the kelp has access to everything it needs to grow big: inorganic nutrients like nitrogen and phosphorous from the sea and enough sunlight. No fresh water, feed or fertilizer is needed. It also doesn’t use up any land, so there are many benefits. Did you know, for example, that algae in the sea produce most of the world’s oxygen? And that kelp is more efficient at capturing carbon than rain forest?

From millimetres to metres

By the time the cuttings are put into the sea, they have already been standing for 6-7 weeks in large seawater tanks at the cuttings nursery. Located on the island of Reksteren in Tysnes, that is where the sugar kelp cuttings are produced. Before being put into the tanks, they are sown on thin ropes. In the tanks, they grow to around 2 centimetres, by which time they are big and strong enough to continue growing at sea.

Before going into the sea, the thin rope is wound around a bigger rope, which is called the carrier rope. At sea, the kelp grows quickly and vigorously, which is reflected in its weight. By the time it is ready for harvesting, kelp is normally 1-2 metres long, but it can reach up to 4-5 metres. A one-metre length of rope with sugar kelp can have a wet weigh of up to 10 kg. The thick rope is therefore needed to carry the weight of the harvest-ready kelp.

The kelp cuttings are rolled around a spool of thin rope before being put into the sea.

What is sugar kelp?

Sugar kelp (Saccharina latissima) is a kind of alga. It is brown and elongated, with rhizoids. It is the most common type of seaweed in Norway, which is home to somewhere in the range of 5-25% of the world’s sugar kelp. According to a Norwegian field study handbook, the species is very common along the whole coast, and particularly in sheltered areas. Sugar kelp has a wide geographical distribution across the Arctic, North Atlantic and Pacific.

What is the kelp used for?

When the kelp is harvested in May, it is fermented and sent to Denmark for use in feed for farm animals, including cattle. Cattle produce very high methane emissions, and if they eat kelp, it actually means they burp (and fart) less!

“Kelp has also been shown to improve the intestinal health of piglets, reducing the need for antibiotics”, concludes Sunniva.

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