The species of the Baltic Sea are unique

The Baltic Sea is home to many resilient organisms. Its flora and fauna include both marine and freshwater species, alien species, and sometimes completely new acquaintances. Check out the inhabitants of the Baltic Sea!

The species is the basic unit for classifying biota. Individuals of any one species are capable of breeding with one another and producing fertile offspring.

Although species identification is usually based on the physical characteristics of each species, comparing only external features is not enough to reliably distinguish all species from each other. In such cases, identification depends on genetic differences instead.

New species have been found even in recent years

Species evolve and change as they multiply. They spread to new areas on their own or with human assistance. While the well-established species of the Baltic Sea are quite well known, new species have been found even in recent years, particularly among smaller organisms.

An invasive species is one that is new to the Baltic Sea or to Finnish coastal waters but is believed to have spread naturally to the area. Species that have travelled greater distances with human assistance are called alien species.

New species compete regionally with established species for both space and food. They can cause changes in local food chains and sometimes even in environmental conditions.

The species of the Baltic Sea are special

The species of the Baltic Sea are unique in many ways. First, as a sea, the Baltic is very isolated. The natural species migration to the Finnish shores occurs mainly through the narrow Danish straits, or from freshwater lakes in the catchment area.

Second, the water in the Baltic Sea is brackish, i.e. the salt content is too low to be seawater but too high to be considered freshwater. The Baltic Sea is at its most saline off the coasts of Sweden, Denmark, and Germany, from where salinity then decreases moving north and east. In the inner reaches of the Bay of Bothnia, the water has almost no salt whatsoever.

The third peculiarity of the Baltic Sea is related to temperature: almost the entire northern Baltic Sea, including the Finnish coast, freezes during winter. This sets specific demands upon the biota. For a species to survive in Finnish marine areas, it must first reach the place and then adapt to a brackish environment that is periodically covered by an ice sheet. A surprisingly large number of species can achieve this!