Researchers at the University of Gothenburg have discovered 20 unique species and subspecies of sea lettuce (Ulva) across the Baltic Sea, including three invasive species. This discovery, published in Algal Research, is crucial for the expanding aquaculture industry and blue economy, as sea lettuce is known for its easy reproduction and rapid growth. The study aims to prevent the introduction of non-native species, which could harm native biodiversity, by providing a basis for strain selection and regulations in sea lettuce aquaculture.