The Baltic Sea and its state

The Baltic Sea is a young and ecologically very sensitive marine area. In terms of volume, it is the world’s second largest inland body of brackish water, and in addition to the Baltic Sea itself, it includes large bays such as the Gulf of Bothnia, the Gulf of Finland and the Gulf of Riga.

Turun kaupungin kuvapankki Sirke Niemelä
Photo: City of Turku, Sirke Niemelä.
In addition to its unique nature, the Baltic Sea is unfortunately also one of the most polluted bodies of brackish water. The Baltic Sea’s susceptibility to pollution and to poisons is due to its shallowness and shape, the small volume of water, and the poor water exchange. The average depth of the Baltic Sea is just 55 metres and it is estimated that a complete exchange of water takes around 30 years.

Eutrophication is regarded as being one of the greatest and most serious threats. The most visible signs of this are the plentiful algae blooms that occur almost every summer, and the slime that gets on beaches and fishing nets. Eutrophication is mainly due to the high loading coming from the catchment area, which is around four times the size of the surface area of the sea. There are 14 countries and around 90 million residents in the catchment area. There is a great deal of industry and agriculture in all the surrounding countries, and therefore both nutrients and environmental poisons have entered the sea over several decades.

As a result of eutrophication, the dead algae that sinks to the seabed consumes oxygen as it decomposes, and there has been an increase in the seabed areas where oxygen is depleted. Up to a third of the entire Baltic seabed suffers from oxygen depletion. In these conditions of oxygen depletion, more nutrients dissolve in the water, which leads to even further eutrophication. Even as the external loading decreases, the internal loading will continue for a long time, and the improvement in the state of the sea is slow.

The Gulf of Finland is the area where eutrophication is greatest, and it will not be able to withstand its current nutrient loading, which is three times greater than that of other areas of the Baltic Sea. According to the latest research results, in summer 2006 the oxygen-depleted area of the Gulf of Finland was exceptionally large, and the state of the seabed was worse than it has ever been during the 2000s. Furthermore, there was hydrogen sulphide in the water close to the seabed over the whole area of the Gulf of Finland. Oxygen depletion will always cause the internal phosphorous loading to start up, when the stratification of water masses create favourable conditions for this.

Although it has been possible to reduce the loading of organic material, nutrients and various environmental poisons entering into the Baltic Sea, especially during the last two decades, the nutrient loading from Finland as well as from the other surrounding countries is still too high in terms of ecological balance.

The last decades have also shown that there have been great changes in the Baltic Sea and the waters have worsened over the entire Baltic Sea area. Achieving a permanent improvement calls for a significant reduction in phosphorous and nitrogen loading over the entire Baltic Sea catchment area.