Baltic Sea

The Baltic Sea is a marginal sea of the northeastern Atlantic Ocean, with limited water exchange between the two water bodies. It is considered one of the largest brackish water bodies in the world and its salinity is significantly lower than of the ocean water, defining its inherent low biodiversity. As saltwater is denser than freshwater, the bottom of the Baltic Sea is saltier than the surface. This creates a vertical stratification of the water column, a halocline, that represents a barrier to the exchange of oxygen and nutrients and fosters distinct marine environments. Valuable fisheries for demersal and pelagic fishes are supported, with many countries exploiting the area. The Baltic Sea is a well-studied ecosystem with many stock assessments available that geographically cover the sub- basins of the entire sea. The status and dynamics of several ecosystem components have been studied in the Baltic Sea including alien species, fisheries, and climate change.