Article image

Biologists discover 20 new species of sea lettuce, a potential new food source

In the chilly waters of the Baltic Sea region and Skagerak, researchers have made a discovery about sea lettuce that will forever alter our understanding of marine biodiversity. 

The team from the University of Gothenburg has revealed that the number of species of the green alga, commonly known as sea lettuce, is significantly larger than previously recognized. Their comprehensive survey covered a staggering 10,000 kilometers of coast, unearthing a remarkable twenty species of this seemingly common algae.

Sea lettuce, a member of the green macroalgae family under the genus Ulva, thrives in this region. The algae extend from the Atlantic waters and reach as far as the Bay of Bothnia in the Baltic Sea, marking their nearly ubiquitous presence.

Sea lettuce could be a valuable food source

Due to its capacity to reproduce easily and grow rapidly, sea lettuce piques the interest of the burgeoning aquaculture industry. Currently, extensive research is underway in Sweden and around the globe to harness this alga’s potential. The industry is exploring opportunities for utilizing sea lettuce in food and various biochemical applications.

While the existence of multiple species of sea lettuce was acknowledged, the exact count remained elusive. Prior to this research, scientists could only identify a few species. 

“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,” said Sophie Steinhagen, a researcher at Tjärnö Marine Laboratory. “We found 20 unique species and subspecies. Three of these are invasive species that have found their way here in various ways.”

What’s more surprising is that some of the newly found species have never been scientifically described before. Certain species seem to be exclusive to the Baltic Sea, enhancing its uniqueness.

Importance of this sea lettuce discovery

The implications of this research are profound, especially for the rapidly growing sea lettuce farming industry. Ignorance can lead to the inadvertent introduction of foreign species, posing a risk to the local ecosystems. It is imperative to understand the diversity of species present along the coasts to safeguard these valuable habitats from invasive species.

“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,” said Steinhagen. “We have not been able to see the real extent of the biological diversity.”

The discovery of new species offers valuable insights for the cultivation of sea lettuces, particularly in new locations along the coast. To maintain ecological balance, it’s crucial to grow the right species at the right place.

Armed with this new knowledge, scientists can formulate effective strategies to preserve unique sea lettuce species specific to a 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,” said Steinhagen.

With this groundbreaking research, the University of Gothenburg team has opened new avenues in our understanding and preservation of marine biodiversity.

More about sea lettuce

Sea lettuce, which is primarily from the Ulva genus, is a type of green algae commonly found in the shallow, coastal waters of the world’s oceans. They belong to the family Ulvaceae, a group of macroalgae or seaweeds that also include other green algae.

Here are some key points about sea lettuce:


Sea lettuce typically appears bright green and forms thin, flat, leaf-like sheets up to about 30 centimeters across. The sheets are usually ruffled and often split into lobes, giving them a lettuce-like appearance, hence their name.

Habitat and distribution 

Sea lettuce is nearly ubiquitous in both temperate and tropical waters across the globe. It thrives in a variety of environments, including brackish waters, and can be found in the intertidal zone (the area of the shore exposed to air at low tide and covered with seawater at high tide) attached to rocks or other hard substrates. It can also grow free-floating in the water column.

Reproduction and growth

Sea lettuce reproduces both sexually and asexually. In sexual reproduction, it releases gametes into the water, which combine to create a new organism. In asexual reproduction, fragments of the algae, known as thalli, can continue to grow and develop into new sea lettuce. This algae is known for its rapid growth and ability to colonize new areas quickly, especially in areas with high nutrients.

Ecological role 

Sea lettuce plays a significant role in its ecosystem. It provides food and habitat for a variety of marine creatures, including mollusks, crustaceans, and small fish. However, in areas with excessive nutrient pollution (eutrophication), sea lettuce can grow out of control, forming large “blooms” that can suffocate other marine life by depleting oxygen levels in the water.


Sea lettuce is edible and has been used in various cuisines, particularly in Asian countries. It’s rich in protein, soluble dietary fiber, and a variety of vitamins and minerals, including Vitamin A, iron, and iodine. It’s also being studied for its potential in biofuel production and other industrial applications due to its fast growth and high bio-mass production.

Recent discoveries

Recent research, as you’ve noted earlier, has found greater diversity within the sea lettuce species than previously understood. The study uncovered that there are potentially 20 unique species and subspecies in the Baltic Sea region alone. This underlines the importance of conserving and understanding these organisms, as they can be crucial to their local ecosystems and have important implications for aquaculture.

Image Credit: Sophie Steinhagen


Check us out on EarthSnap, a free app brought to you by Eric Ralls and

News coming your way
The biggest news about our planet delivered to you each day