Sea lettuce consists of many species of the green algae Ulva. In Sweden, sea lettuce grows on cliffs and rocks at the edge of water along the entire West Coast and in the Baltic Sea up to the Bay of Bothnia.

Sea lettuce is very nutritional with relatively high protein content, healthy polyunsaturated fatty acids and dietary fibres. It also has valuable biochemical molecules. Research is ongoing both in Sweden and abroad for utilising sea lettuce in the food industry and for different biochemical applications.

Researchers at the University of Gothenburg have surveyed 10,000 kilometres of coast and found twenty species of sea lettuce.

Sophie Steinhagen, a researcher at Tjärnö Marine Laboratory said:

“We have studied the biological diversity of the Baltic Sea, Kattegatt and Skagerak by taking a large number of samples from sea lettuce that we have then conducted DNA analysis of. We found 20 unique species and subspecies. Three of these are invasive species that have found their way here in various ways.”

The researchers also found completely new species of sea lettuce in Swedish waters that have not previously been described scientifically. Some of these appear to only grow in the Baltic Sea.

The importance of this survey is significant. Growing sea lettuce as a food source is a rapidly increasing industry, and foreign species risk being spread through simple ignorance. To maintain and protect valuable ecosystems along the coasts, it is important to know which species grow there and to not introduce new species that risk out competing the native species.

Sophie Steinhagen explained:

“Our study shows that today’s method of identifying species, which is often done by looking at the appearance of green algae, is insufficient for identifying the distribution of the various species. We have not been able to see the real extent of the biological diversity,

“This new knowledge allows us to develop methods for maintaining the unique sea lettuce species along a specific coast. Our survey can also help when writing regulations related to invasive species that should not be used in aquaculture if it is to be sustainable. “

Click on this link to access Molecular identification of the ubiquitous green algae Ulva reveals high biodiversity, crypticity, and invasive species in the Atlantic-Baltic Sea region, published in Algal Research