About » The Baltic Sea as a particularly vulnerable sea region


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Part-financed by the European Union

The Baltic Sea is a landlocked (intra-continental), shallow (average depth of 52.3 m, and maximum depth of 459 m, Landsort Deep) brackish sea with hardly any tide (around 24 cm in Copenhagen) in the northern part of Europe. The surface area of the Baltic Sea is 415,266 square km; it holds 21,721 cubic km of water.

The Baltic is geologically young - it is estimated to be 12-13 thousand years old.The sea, as we know it today, dates back to around 3000 years ago. It extends 1,500 km from west to east, which explains the relatively high diversification of climatic conditions between the southern and the northern part of the Baltic (long winters with heavy snow falls and large ice cover in the north, and short winters, little snow and small ice cover in the south).

The Baltic Sea consists of the Gulf of Bothnia (divided into Bothnian Bay, Bothnian Sea and the Archipelago Sea), the Gulf of Finland, the Gulf of Riga and the Baltic Proper in the centre. The Baltic Sea and the Northern Sea are connected by the Danish straits (Oresund, Great Betl and Little Belt) and Kattegat and Skagerrak (the Belts).

Due to restricted water exchange between the Baltic and the Northern Sea, the residence time of water is 25-30 years.The Baltic Sea is fed by around 250 rivers, and the combined average water flow rate of all the Baltic Sea catchment rivers is about 15,190 m3/s, or 497 km3 annually (plus precipitation water supply); the biggest rivers are: Neva, Vistula, Neman, Daugava, Oder, Gota, and Kemi.Due to limited free water exchange and high riverine water discharges (the Baltic Sea level is 10-36 cm higher than that of the Northern Sea), the Baltic Sea is the largest brackish (mesohaline) water reservoir in the world of low salinity of up to 7 prom. (medium salinity of ocean water is 35 prom.) (in the Baltic Sea, the salinity diminishes in the north-east direction and increases with depth).

Another consequence of riverine water discharges that blend with heavier saline water from the Ocean in the bottom layer is the vertical stratification of salinity, which further restrains vertical water diffusion, ventilation and oxygenation. The Baltic Sea has a very sharp gradient on oxygen concentration (oxycline), below which water oxygenation is heavily reduced (deepwater oxygenation can be down to zero at the depth of 140 m); instead, hydrogen sulphide is present, a by-product of microbiological and chemical processes taking place at anaerobic conditions.

The Baltic Sea (photo by NASA, 1999)

All of these factors translateinto a compromise between conditions which are optimum for fresh water and saltwater species. The biocenotic diversity of the Baltic Sea is lower (around 30macrofaunal species/10 km2) as compared to open (non-enclosed) seas(as many as 800 macrofaunal species/10 km2 in the most diversifiedsea ecosystems) or fresh water ecosystems.It is estimated that the Baltic Sea has around several thousand species,the majority of which are plankton organisms.

The Baltic Sea has a highlydiversified coastline - from sandy flat beaches and dunes, to rocky skerries,spits, lagoons, fjords, sandbars, cliffs, as well as human-changed coastsaffected by anthropogenic factors. The coastline of the Baltic Sea is around8100 km long and is made up of numerous gulfs, lagoons, bays, spits,peninsulas, lakes, islands and archipelagos (there are around 25,000 islands inthe archipelago in the Stockholm area).

The distinctive characteristicsof the Baltic Sea (shallow, semi-enclosed, brackish water, coastline diversity,cold climate, heavy traffic, ecological vulnerability, intensive fishery, highrecreation value, undiscovered risk from chemical weapons dumped into theBaltic Sea during World War II, low biodiversity, oxygen stratification,limited water exchange with the World Ocean) make it a maritime ecosystem whichis unique worldwide, but make the natural water self-purification processesmuch less effective as compared to open sea and ocean waters. In considerationof the high population density, high industrialisation and intensiveagricultural activities in the Baltic Sea catchment area, the Baltic isconsidered one of the most heavily polluted seas in the world.

In consideration of the foregoing,the International Maritime Organization (IMO) and the United Nations agendanamed the Baltic Sea a Particularly Sensitive Sea Area (PSSA). A Particularly Sensitive Sea Area (PSSA) isan area that needs special protection because of its significance forrecognized ecological, cultural, socio-economic or scientific reasons and whichmay be vulnerable to damage by international maritime activities (the volume ofmaritime traffic in the Baltic Sea is one of the highest in the world). TheBaltic Sea is counted among the most precious and most environmentallyvulnerable sea ecosystems in the world, among the Galapagos Islands, the GreatBarrier Reef, and the Canary Islands.

With the PSSA status, theBaltic has been covered by special protection standards, such as closure ofroutes to certain types of vessels or cargoes, seasonal closures to protectanimals, speed restrictions, recommendations for open sea routes. Thesemeasures are aimed at limiting the risk of maritime accidents and the resultingoil spills.

Selected coastline landscapes of the Baltic Sea (photo by Wilson M.A., Wikipedia)

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Coalition Clean Baltic
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Project Industrial animal farms in the Baltic Sea Region - sustainable practices to reduce nutrient loads is a part of a long-term campaign of the Coalition Clean Baltic and Green Federation "GAJA", aiming to reduce the negative impact of large-scale animal production on the environment and local communities in the Baltic Sea Region, particularly by reducing nutrient run-off into the sea. The project is part-financed by the European Union. This website reflects only the view of the Coalition Clean Baltic. The Executive Agency for Small and Medium-sized Enterprises (EASME) is not responsible for any use that may be made of the information it contains.