In the archipelago, people have always lived in close relationship with the sea. Considering its size, geology, nature and history, the Archipelago Sea is a unique place on Earth. The sea area extends from the Åland’s largest island to the Finnish mainland. The sea is shallow and has brackish water with a low salinity, which strongly affects both the species composition and the condition.
The bladderwrack belt, the blue mussel reef and the seagrass meadows are three crucial environments in the Archipelago Sea. Like in the forests above the water’s surface, the bladderwrack below the surface is teeming with life. In addition to fish, a large variety of animals such as Baltic isopods, gammarid amphipods, Baltic prawns, mussels and snails live among the bladderwrack. These animals use the seaweed both as protection and as a place to find food. The bladderwrack, the largest algae in the Baltic Sea, is also an indicator species that reflects the state of the Baltic Sea. Blue mussels live in large colonies, which cover areas from a few square metres to several hectares, and they are estimated to filter an amount of water equivalent to the entire water volume of the Baltic Sea each year. The blue mussel is a good indicator of changes in water quality, as it absorbs nutrients and pollutants from water. Seagrass meadows are important for the diversity of nature. They offer a habitat and safety for a number of different species. Seagrass meadows can bind 35 times more carbon dioxide than the corresponding area of rainforest.
The Archipelago Sea is currently facing many challenges. An overload of nutrients leads to strong algal blooms, large occurrences of blue-green algae, a change in the balance between different species, as well as dead seabeds. Invasive alien species, which establish themselves and compete with the native species, also affect the balance.
Can you balance like this?
Did you know? The white-fingered mud crab, commonly called the Harris mud crab (Rhithropanopeus harrisii), came to Finland from North America by cargo ship and can therefore be seen as an alien species in the Baltic Sea. The crab was found for the first time in Naantali in 2009.
To be able to protect the Archipelago Sea, knowledge is needed. There are two marine biological research stations in the biosphere reserve. Åbo Akademi University has one in the Korpoström Archipelago Centre and the University of Turku has one on Själö in Nagu.