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.
Salinity and Fucus distribution in the Baltic Sea
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.
Baltic Sea Weed Blog 
Nice data,
I am doing a research on osmotic power and I would like to ask you where can I get georeferenced of salinity of the Baltic and the North Sea?
Thanks a
Thank you David.
For georeferenced data on the Baltic Sea, I recommend that you look at the HELCOM reports. They are all found and available at their website.
I also find the map in Feistel et al. 2010 very helpful, although it is quite a large grid.
Cheers!
Radicans,
I too am looking for salinity data for both the Baltic and North Sea. Is your map bottom or surface salinity? At the HELCOM website, I could only find bottom salinity data.
Cheers,
Keith
Hi Keith!
The map is a V-E-R-Y generalized surface salinity. For much better resolution, check out Feistel et al. 2010. If you know (or know someone who does know) Swedish, there is a lot of such data available from http://www.smhi.se the Swedish weather site, and also on the collective site for all things marine/brackish http://www.havet.nu. Also, try some of the HELCOm publications, I seem to remember a map of the halocline stratifiaction somewhere…. Sorry to not be of much help.
Cheers
Ellen