The Baltic Sea is unique!

The Baltic Sea is one of a kind: geologically young, one of the largest bodies of brackish water, severely disturbed, but at the same time precious with a unique mixture of sea and freshwater species. This valuable area host over 85 million people.

The state of the Baltic Sea is alarming. The most concerning problem is eutrophication, but also alien species, and oil and chemical freighting present serious threats to the region. There is a common concern about the state and the future of the Baltic Sea, and some political steps to react to the challenge have been taken.

The value of the Baltic Sea is innumerable. The sea offers many ecosystem services, such as regulation of climate and water circulation, pollution control and maintain of biodiversity. Besides the ecosystem services, the Baltic Sea´s value consist e.g. of:

• economical value
• cultural value
• aesthetic value
• intrinsic value

Lakish sea

The Baltic Sea is a curiosity among the seas: it is more a giant lake than a sea. Compared to oceans, the Baltic Sea has practically no tidal variation in the sea level. Most notably, the salt concentration is low. Salinity varies from 20 psu (35 psu in the oceans; practical salinity unit, parts per thousand, 20 psu means 2,0 % salt concentration) to 6-7 psu in the Baltic Proper and almost fresh water with 1-3 psu in the back ends of the Bothnian Bay and the Gulf of Finland.

The Baltic Sea remain low in salinity due to constant runoff from over 250 major rivers. Without episodic supplement of salty water from the North Sea through shallow Danish Straits, the Baltic Sea would turn eventually into a lake.

Sea living on the edge

The Baltic Sea is not homogenously “lakish”. There are many gradients and physical barriers. These are the key to understanding the nature and the behaviour the sea.

Salinity and temperature gradients from south to north, from west to east, and from bottoms to the surface layers define which organisms inhabit the area. The Baltic Sea is a unique mixture of sea and freshwater species. The number of species tolerating the brackish water and a highly variable environment is low, though. And those marine species which live on the edge of their tolerance limits, remain smaller in size compared to ocean conditions.

The most polluted sea in the world?

The special characteristics of the Baltic Sea, such as shallowness, poor turnover of the water, and bottom sills, make it vulnerable to pollution and other human disturbances. The sea is truly a sink to many pollutants and nutrients originating from the agriculture.

The most alarming problem arises from eutrophication – an excess of nutrients causing high algal production with many side effects. But also alien species intruding the “natural” biocommunities, and oil and chemical freighting present serious threats.

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