The Baltic Sea
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 but the average depth is only about 55 m. A complete exchange of water takes around 30 years.
Due to the low saline brackish water, the biota is living close to its tolerance limits. This coupled with a strong vertical stratification and slow exchange of the water, depletion of oxygen is a commonly occurring stress factor for the biota.
The combination of the factors above makes the nature of the Baltic Sea unique; however, it also make the Baltic Sea vulnerable. Unfortunately the sea is one of the most polluted water bodies in the world. Due to its shallowness and shape, the small volume of water, and the poor water exchange, it is particularly susceptibility to additional environmental stresses such as nutrient enrichment (eutrophication), pollution and toxic or harmful substances.
At present, the Baltic Sea is being burdened most by the nutrient loadings and by hazardous substances, and also by the greatly increased amount of shipping.