Brackish water

In brackish water is understood lake or sea water with a salinity of 0.1 % to 1 %.

In the Anglo -Saxon is a salt content (salinity ) between 0.05 % and 1.8 %, set partly also 3%. Water with lower salinity means fresh water, water with higher salinity salt water. Brackish water differs from fresh water, especially in that it contains (despite its comparatively low salinity) too much salt to be drinkable for people.

The word brackish water derives from the Low German word Brack. This denotes a body of water that was created by a dike breach and subsequent cratering.

Ecology

In the area of estuaries in the sea caused by the mixing of the sweet river water with the salty sea water, the so-called brackish water zone. This is characterized by a constantly changing salinity and thus represents the organisms that live there because of the changing osmotic pressure greatly increased demands on the regulation of their water and salt balance ( osmoregulation ). Meet here - depending on the salinity - freshwater tolerant species from the sea and salt water tolerant species from the freshwater. Some plant and animal species have developed the ability to survive in the brackish water conditions, such as

• Fish: flounder, pike, perch, smelt
• Crabs: Chinese mitten crab, mud shrimp ( Corophium volutator ), barnacle ( Balanus improvisus ), shrimp ( Palaemon longirostris and Palaemonetes varians ), marine isopod ( Jaera albifrons )
• Turtle: Diamondback Terrapin
• Molluscs: Mussel (Mytilus edulis)
• Polychaetes: the marine annelid worm ( Nereis diversicolor )
• Oligochaeta: Nais elinguis
• Flowering plants: Ordinary beach ledges ( Bolboschoenus maritimus )
• Diving beetles ( Dytiscidae ): Big bank wet beetle

The brackish water zones are inhabited, usually by a few highly specialized species, but in a high population density. In this ecosystem, so there is a high density of individuals at a relative low species diversity (low biodiversity).

Occurrence

Typical brackish water zones one finds

• In the eastern part of the Baltic Sea, particularly in the Gulf of Finland and the Gulf of Bothnia
• In the southern part of the Baltic Sea, the Pomeranian Bodden landscape, in particular the Darß- Zingster Boddenkette and the North Rügen Bodden.
• Particularly pronounced in the estuary areas of Tidenflüsse such as the Elbe, Weser, Ems, sturgeon, Eider, Rhine, Severn, Seine or Thames; here, the brackish water zone may extend over a length of more than 50 kilometers.
• In the lowest estuary areas of lowland rivers such as the Oder ( Szczecin Lagoon ), and Weichsel ( Vistula Lagoon ), which open into the barely influenced by the tide Baltic Sea.
• In the area of submarine sources ( for example, on the Adriatic coast in Croatia)

Even in the tropics brackish water zones form in the sphere of influence of estuaries; they are often characterized by extensive mangrove swamps.

In the interior, it may result in the formation of brackish water by leaching of salt deposits. This can be done of course as by humans (mining waste water from salt mines ). In this way the Werra and Weser were in the second half of the 20th century in the upper and middle reaches to temporarily brackish rivers.