Unlocking economic potential of the Ulva crop for low salinity environments: exploring the effect of salinity gradients on the performance and valuable compounds of Baltic Sea strains

Journal article, 2025

The rising global significance of sea lettuce (Ulva spp.) in aquaculture stems from its versatility, rapid growth, and nutritional benefits. Cultivation expansion into lower salinity areas, like the Baltic Sea, is crucial for advancing aquaculture beyond traditional environments. This study investigated the impact of long-term (8 weeks) low salinity treatments on the biochemical content of eight Ulva strains - encompassing some of the most common Ulva crop species (Ulva lacinulata, Ulva linza, Ulva intestinalis, Ulva fenestrata) of the wider Baltic Sea area - from varying source salinities (30, 14, 9, 7). Most strains exhibited significantly higher growth rates and contents of crude protein under low salinity treatments, irrespective of where they came from (i.e. euhaline or mesohaline environments). However, effects on pigments and phenolic contents were strain-specific. Ulva lancinulata showed high resilience to salinity changes. Cultivating Ulva under low salinity conditions enhances its nutritional attributes and identifies the broader Baltic Sea as a viable cultivation environment. Nevertheless, careful selection of strains is crucial due to significant inter- and intraspecific differences. This research underscores the importance of tailored cultivation strategies for optimizing Ulva biomass production, particularly in the context of the expanding Blue Economy industry.