Breton seaweed, a crop of the future

Audio 02:28

The thallus, or leaf, of a kelp.

The algae feeds on light, by photosynthesis, and mineral elements present in seawater by absorbing them directly through the entire surface of the thallus.

© RFI/Agnes Rougier

By: Agnes Rougier

8 mins

Seaweed, cultivated for food and industry, is mainly produced in China and Indonesia.

Faced with this intensive production, Europe is supporting quality organic seaweed farming in which Breton producers have embarked.

Today, Breton seaweed, grown organically and in open water, has gained international fame.

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From our special correspondent in the region,

In Brittany, wild seaweed was traditionally picked to be used as fertilizer in the fields, the region has become the leading producer of cultivated seaweed in France.

In northern Brittany, in the Rance estuary – a Natura 2000 classified site – near the village of Saint-Suliac, Magali Molla and Jean-François Arbona, both former marine biologists, were pioneers: in 1983, they embarked on organic seaweed farming by creating their open-water seaweed production and marketing company,

 : " 

 ,” says Jean-François Arbona.

With almost 40 years of hindsight, they testify to the beneficial effects of seaweed farming on the marine environment: every year in the spring, their concession of twelve hectares in deep water teems with fish and shellfish that come to reproduce there.

Laminaria, a local seaweed

The seaweed grown in the Rance estuary is kelp,

.

The kelp is made up of three parts: the holdfast, which it uses to hold on to, the stipe, a flexible stem like a reed to avoid breaking by the force of the waves and the current, and the thallus or frond – the leaf – the consumed part, which can be up to 4 meters long.

The algae feeds on light, by photosynthesis, and mineral elements present in seawater by absorbing them directly through the entire surface of the thallus.

In Brittany, where waves and tides stir up the seabed, the water is disturbed by suspended sand which prevents the sun's rays from penetrating deeply.

To compensate for this lack of light, kelps are grown near the surface, but deep enough to remain under water at low tide, they never emerge.

An extraordinary reproductive system

To produce young shoots of algae, or seedlings (like a farmer produces seedlings of tomatoes before putting them in the ground), seaweed farmers must master their complex system of reproduction: " 

 , ”says Magali Molla, who takes care of it at C-Weed.

Laminaria are digenetic: their life cycle includes two generations.

Adults, they produce male and female spores.

The spores are collected in collectors by the algoculturists, then transferred ashore in the seawater tanks of the hatchery.

There, these spores develop into male and female filaments – gametophytes – which fertilize to form an egg.

This egg will then divide several times, until it forms a seedling.

Diagram of the reproduction cycle of kelp algae.

© Magali Molla

Magali Molla then introduces cords into the vats on which the seedlings will hang their crampons, then Jean-François Arbona will tie these cords on large ropes fixed at sea.

Lined up like swimming pool lanes, in the direction of the current, these ropes form the "lines", on which the kelps will grow quietly until harvest in the spring.

Algae, a vast field to be cleared

Not only are these algae good to eat and excellent for your health – rich in mineral salts and proteins –, but they are also made up of many very useful molecules: their gelling properties are used in the food industry – in yogurts and other creams –, their moisturizing and soothing properties, in cosmetics.

But they contain many active ingredients whose applications have yet to be discovered

The European Union project GénialG

, coordinated by the CNRS biological station in Roscoff, is a participatory project that brings together partners in 19 European countries, including C-Weed.

GénialG

aims to identify and extract molecules of interest from algae with the aim of developing the entire sector, from seaweed farming to industrial applications.

Launched in 2017, the project has already produced results: " 

 ", says Kévin Cascella, research engineer at the Roscoff station, " 

.

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A marine forest

The European specifications on organic production

prohibit inputs and allow clean aquaculture, which stands out in particular from industrial salmon farming.

Cultivated in water whose quality is regularly checked by

, the algae sectors resemble aquatic forests, they allow the creation of a complete ecosystem: prey come to hide there and predators pursue them, crustaceans and molluscs reproduce there, “ 

 ”, assures Kévin Cascella.

By capturing carbon dioxide and releasing oxygen – it is estimated that all the aquatic plants on the planet produce 70 to 80% of the oxygen in the atmosphere – algae also help fight global warming. climatic.

The researcher likes to compare a chain of seaweed to a marine forest: “ 

 ”.

Breton seaweed has a future

The development of the seaweed farming sector is supported in particular by the Regional Council of Brittany (

program ) and the

.

At the same time, several scientific applied research programs funded by the European Union (

,

) or

(

,

) are interested in the natural compounds of algae.

Today, seaweed farmers bear witness to this and scientific research validates it: the cultivation of seaweed, as practiced in Brittany in protected areas, is beneficial for biodiversity and the climate.

Ecological, recognized for its quality, with the promise of more and more outlets, Breton seaweed farming therefore has a future.

And Jean-François Arbona concludes: " 

" .

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