Sophie sits in a boat pulling a rope with sea lettuce.
Sea lettuce grows quickly in the spring when the water is still cold, and the days have become longer. In the Kosterhavet farm, the algae grow on thick ropes around which the researchers have wound thin lines with algal spores.
Photo: Björn Larsson Rosvall

Sophie is plumbing the depths of future foods


Algae researcher Sophie Steinhagen has been interested in plants ever since she grew up on a farm in central Germany.
“But it wasn’t until I attended a lecture on algae that I realised there was as much to explore below the surface of the sea as above it.”

Sophie Steinhagen dips her right hand into a plastic cylinder and fishes out a handful of sea lettuce. She is standing in a refrigerated room on the ground floor of the Tjärnö marine laboratory. The shelves along the walls hold rows of water-filled cylinders of sea lettuce of various ages.

“We were previously unable to pre-cultivate macroalgae in culture. But now we can grow sea lettuce, for example, quite effectively,” says Sophie Steinhagen.

The cultivation of algae for food production is a major reason why she settled on her field of research. Protein-rich underwater plants have almost infinite potential, according to Sophie.

“We have food shortages in many countries and climate change has led to droughts that affect traditional food production on land. Algae farming could be a major part of the solution to future food needs. Algae farming is the fastest growing sector of aquaculture in the world, and I have already seen algae being sold in an Ica supermarket.”

Can be grown more densely than land crops

There are many advantages. The seaweed gets its fertiliser directly from the sea and the areas available for cultivation are large. Algae can be grown more densely than land crops, which contributes to yields several times higher per hectare than for cultivation on land. The EU has also realised this and is now investing significant resources in a sustainable blue economy that is no longer just about fisheries.

Bild på havssallat med hål
The algal spores appear as a darker shade of green along the edges of the holes in the sea lettuce.
Photo: Björn Larsson Rosvall

Sophie Steinhagens research into algae began in Germany. During her PhD studies at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, she inventoried the species of algae growing in the Baltic Sea and North Sea. Now she has made the same inventory along Sweden’s West Coast. Using DNA technology, she has identified a number of new species. Previously, a handful of species of sea lettuce were known on the West Coast. Now there are 19.

“It’s important to know which species are present in order to detect and monitor invasive species that arrive via ships’ ballast tanks, for example. Some of these species cause devastating algal blooms that can cover entire beaches and kill off other life. This in turn affects biodiversity and can disrupt ecosystems.”

By studying the properties of algae, Sophie and her colleagues can find out which species are best suited for cultivation. In a bay in the Kosterhavet National Park, sea lettuce is being cultivated for research purposes. The sea lettuce grows on thick ropes hanging 1-1.5 metres below the surface of the water. In March and April, when the days lengthen but the water is still cold, there is an explosion of growth.

Like thin sheets of paper

On a sunny day in early April, Sophie Steinhagen hangs over the side of a rubber dinghy and fishes up a rope of algae planted in September. The sea lettuce is bright green, and completely free of any other algal growth. The texture is a little like that of a thin sheet of plastic.

“We leave them for a few more weeks before harvesting and by then they will have doubled in size. We already use algae in various foods, but at the moment we import most of it from Asia and that’s unnecessary.”

Sophie Steinhagen believes that aquaculture is important on many levels. Around our coasts there are many fishing villages in which the boats are permanently beached and there is depopulation. In the future, algae farming can bring communities back to life. There are nine countries around the Baltic Sea that have a coastline and there is a lot of interest in algae farming,” says Sophie. But in its brackish water, other species of sea lettuce can be grown. Gutweed is one such species that researchers are looking at.

“This is not just about algae as a protein-rich food alternative. The carbohydrates in algae can be used to make surgical thread, for example. Perhaps we can develop a future packaging material from the sea? Algae do not contain lignin, a substance that requires environmentally harmful processes when paper is made from trees.”

Multitrophic cultivation

She emphasises that it is important not to copy current onshore farming methods. Large single-crop fields lead to monocultures that deplete biodiversity. Crop rotation, and not just with different crops, is the recipe. By combining the cultivation of algae, mussels, sea cucumbers and fish in the same water, ecosystems and diversity can be preserved while aquaculture yields are maintained throughout the year.

“Nature has taught us that multitrophic cultivation is best. There are many organisms living among seagrass, seaweed and sea lettuce and we need to understand how everything interacts.”

Thanks to the Swedish Mariculture Research Center (SWEMARC) and the Centre for Sea and Society at the University of Gothenburg, Sophie sees great opportunities for her research to lead to concrete results for the community.

“Its interdisciplinary centres are the best thing about the University of Gothenburg. I value the fact that researchers from different disciplines collaborate with, for example, Chalmers and the Swedish Food Agency – very highly.”

Plants from the sea for human use

THEN: In the British Isles, algae have been harvested for a long time. Among other things, a pudding is made from red algae and in Scotland bread has historically been baked from algae. In the 17th century, during times of crop failure, algae from the beaches was used to feed the cows. Vikings are said to have used eelgrass as filling in their pillows. Eelgrass has sometimes replaced straw as a roofing material in Denmark and elsewhere.

NOW: In 2019, the European Commission launched the European Green Deal, which aims to make the Union the world’s first climate-neutral region. An important aspect of this is the part of the economy that comes from the sea. The European Green Deal requires investment in new technologies including sustainable food production from algae and seagrass, innovations in cell-based food from the sea, and the restoration of marine ecosystems.  The EU says the investments will create new jobs and businesses. The grants for investments in the blue economy are expected to total more than EUR 300 million.

IN THE FUTURE: “We need to develop species of algae that are hardier and have even better nutritional content. Experiments with feeding algae process water from the food industry for better growth and increased protein content in sea lettuce carried out by the doctoral student Kristoffer Stedt at the University of Gothenburg are one such example. We will also look more at which species are best suited to different needs.”