The Baltic Sea is unique because of its low salinity. In the northernmost parts, the water is almost considered freshwater, whilst the salinity at the entrance/exit in Öresund lies around 15 psu (practical salinity unit, roughly equal to ‰ and denotes salinity). The low salinity of the Baltic Sea makes it a stressful environment for both freshwater and marine species, both groups lives on the very edge of their tolerance of either too high or too low salinity.
The map show surface water salinity and the distribution of the three species from the genus Fucus that can be found in the baltic Sea.
Green denotes bladderwrack (Fucus vesiculosus)
Orange denotes narrow wrack (Fucus radicans)
Yellow denotes serrated wrack (Fucus serratus) Note that for this species only the distribution along the Swedish coasline is shown, since we have not found any data on its distribution in any other countries along the Baltic Sea.
More information will follow.