This is a project for a student who only intends to do a 30 credits Master project. The project is part of the FunkVeg project within Baltic Bridge, the Stockholm - Helsinki universities collaboration. In the FunkVeg project, we try to resolve the functional role of free-living bladderwrack, combining ecological and genetic methods.

Bladderwrack (Fucus vesiculosus) is one of the most important species in the coastal areas of the Baltic Sea. Just like trees in a forest, they provide food and shelter for many small animals, fish and other algae at 0,5-5 metres depth.

Typically, bladderwrack grows attached to hard surfaces under water, such as rocks and boulders. It is therefore usually considered a ‘rocky shore organism’. It is therefore very interesting that free-living, unattached, bladderwrack also exist. These are found mainly in sheltered bays, lying loose on soft sediment bottoms, where we expect to find the rooted vascular plant communities. In the Askö area in Sweden and Tvärminne area in western Gulf of Finland, free-living populations of bladderwrack have been recorded during the last 20 years. They can be extensive (100-1000m2) and seem to occur year after year at the same sites.

So, what role does the free-living bladderwrack play in the Baltic Sea ecosystem? A major one or just “person in crowd”?

The free living bladderwrack forms a perennial structure on soft bottoms. We hypothesize that this will increase the amount of fine particles in the sediment below the bladderwrack, as the bladderwrack structure will slow down the water current and act as a sediment trap. We also hypothesize that the sediment will have a higher content of nutrients (C,N,P) than sediment without bladderwrack.

The field experiment to test these hypotheses were performed in the summer 2017 at Askö laboratory. The free-living bladderwrack treatment was compared to one of loose lying bladderwrack, which is torn off parts beginning to decay, and a control treatment. The sediment was sampled before and after five weeks in the field.

Proposed master project:

Performing analyses on sediment grain size and prepare for CNP-analyses, which will be done by the marine laboratory at DEEP. If the student wishes to expand the study, field sampling of benthic fauna is a possible add-on to the project. Duration: 10-20 weeks depending on student.


Ellen Schagerström