Under brackish water refers to sea water or sea water with a salt content ( salinity ) of 0.1% to 1%.
In the Anglo-Saxon region, a salt content between 0.05% and 1.8%, sometimes even 3%, is assumed. Water with a lower salt content is called fresh water , water with a higher salt content is called salt water . Brackish water differs from fresh water mainly in that it contains too much salt (despite its comparatively low salinity) to be drinkable for humans.
In the area of river mouths in the sea, the mixing of the sweet river water with the salty sea water creates the so-called brackish water zone . This intertidal zone is characterized by a permanently changing salt content and therefore places high demands on the regulation of their water and salt balance ( osmoregulation ) on the organisms living there due to the changing osmotic pressure . Here - depending on the salinity - freshwater-tolerant species from the sea and saltwater-tolerant species from freshwater meet. Some animal and plant species have developed the ability to survive in the brackish water conditions, such as
- Fish : flounder , pike , pikeperch , smelt , archer fish , stickleback
- Crabs : Chinese mitten crab , mud shrimp ( Corophium volutator ), barnacle ( Balanus improvisus ), shrimp ( Palaemon longirostris and Palaemonetes varians ), marine isopod ( Jaera albifrons )
- Tortoises : diamond tortoise
- Mollusks : Blue mussel ( Mytilus edulis )
- Polychaetes : sea ringworm ( Nereis diversicolor )
- Oligochaetes : Nais elinguis
- Flowering plants : common beach ledges ( Bolboschoenus maritimus )
- Floating beetles (Dytiscidae): Large water beetles
The brackish water zones are generally populated by only a few highly specialized species, but with a high population density. In this ecosystem there is a high density of individuals with a relative poverty of species (low biodiversity ).
Brackish water zones can be found in the area of practically all river mouths . Typical brackish water zones can be found in Europe
- in the eastern part of the Baltic Sea , especially in the Gulf of Finland and the Gulf of Bothnia .
- in the southern part of the Baltic Sea, the Pomeranian lagoon landscape, in particular the Darß-Zingster lagoon chain and the northern Rügen lagoon .
- especially pronounced in the mouth areas of the tidal rivers such as Elbe , Weser , Ems , Stör , Eider , Rhine , Severn , Seine or Thames ; here the brackish water zone can extend over a length of more than 50 kilometers.
- in the lowest estuary areas of lowland rivers such as Oder ( Stettiner Haff ) and Vistula ( Frisches Haff ), which flow into the Baltic Sea, which is hardly influenced by the tide .
- in the vicinity of submarine springs (for example on the Adriatic coast in Croatia ).
- The Lexicon of the Earth: Brackish Water .