Scientists find new sea lettuce species while searching Scandinavian shores

13 Jun 2023 --- Packed with protein, polyunsaturated fatty acids, dietary fiber and valuable bioactive and nutritional compounds, sea lettuce could become a major piece of the expanding aquaculture industry. The green macroalgae, of the genus Ulva, are easy to reproduce and quick to grow making it even more attractive for the sector.

A group of scientists who recently set out to catalog different types of sea lettuce along a 10,000 km stretch of shoreline found 20 previously unknown species, reinforcing the need to understand more about the nutrient-dense plants.

“This new knowledge allows us to develop methods for maintaining the unique sea lettuce species along a specific coast,” says Sophie Steinhagen, a researcher at Tjärnö Marine Laboratory in Strömstad, Sweden, and lead author of the study.

“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.”

Weeding out invasive species
One problem the scientists highlight for sea lettuce in the aquaculture industry is invasive species. As research on incorporating the macroalgae into the food system and identifying their biochemical and bioactive applications is currently ongoing in several countries, discovering where and how to grow it is crucial.

Additionally, the researchers explain that, since growing sea lettuce as a food source is rapidly increasing across the aquaculture industry, preventing the spread of invasive species is critical to maintaining and protecting valuable coastal ecosystems. 

In Sweden, some sea lettuce grows on oceanside rocks and cliffs.Knowing which species grow in a specific area and taking care not to introduce new species decreases the risk that native species will die out through competition.

“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,” Steinhagen explains. “We found 20 unique species and subspecies.”

“Three of these are invasive species that have navigated here in various ways.”

An octopus’s garden?
The study, published in Algal Research, highlights that not all sea lettuce grows in the ocean. Some, such as a few of the species in Sweden, grow on cliffs and rocks along the ocean shore.

The researchers further highlight that, though the survey found 20 species that had not previously been scientifically described, most agree that there are still many species and subspecies yet to be identified.

“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,” says Steinhagen.

In related news, a recent study from a team of international researchers found that increasing the consumption of foods that come from the ocean or freshwater environments could address global challenges such as nutritional deficits, disease risk, greenhouse gas emissions and climate change resilience.

At the same time, a study by the Woods Hole Oceanographic Institution found that the impacts of climate change on the ocean could result in a decrease of omega 3 acids available for fish and humans.

Edited by William Bradford Nichols