Brackish water 3336 224369822 2008-07-08T15:36:19Z Tewapack 1370770 /* Notable brackish bodies of water (by type, in alphabetical order) */ {{redirect|Brackish|the Kittie song|Brackish (song)}} '''Brackish water''' (less commonly '''brack water''') is water that has more [[salinity]] than [[fresh water]], but not as much as [[seawater]]. It may result from mixing of seawater with fresh water, as in [[estuary|estuaries]], or it may occur in brackish fossil [[aquifer]]s. The word comes from the [[Middle Dutch]] root ''"brak,"'' meaning "salty." Certain human activities can produce brackish water, in particular certain [[civil engineering]] projects such as [[Dike (construction)|dikes]] and the flooding of coastal marshland to produce brackish water pools for [[freshwater prawn farm]]ing. Brackish water is also the primary waste product of the [[blue energy]] process. Because brackish water is hostile to the growth of most terrestrial plant species, without appropriate management it is damaging to the environment (see article on [[Shrimp farm#Ecological impacts|shrimp farms]]). Technically, brackish water contains between 0.5 to 30 grams of [[salt]] per [[litre]]&mdash;more often expressed as 0.5 to 30 parts per thousand (ppt or ‰). Thus, ''brackish'' covers a range of [[Salinity#Systems of classification of water bodies based upon salinity|salinity regimes]] and is not considered a precisely defined condition. It is characteristic of many brackish surface waters that their salinity can vary considerably over space and/or time. {| style="margin-left:auto; margin-right:auto;" |- ! style="background:#B8E0F6" colspan="4" | Water salinity based on dissolved salts in parts per thousand (ppt) |- ! style="background:#87CEFA" | [[Fresh water]] ! style="background:#87CEFA" | '''Brackish water''' ! style="background:#87CEFA" | [[Saline water]] ! style="background:#87CEFA" | [[Brine]] |- ! style="background:#00BFFF" | < 0.5 ! style="background:#00BFFF" | 0.5 - 35 ! style="background:#00BFFF" | 35 - 50 ! style="background:#00BFFF" | > 50 |} ==Brackish water habitats== ===Estuaries=== [[Image:Monodactylus argenteus.JPG|thumb|A brackish water fish: ''Monodactylus argenteus'']] Brackish is a mixture of sea water and fresh water. An estuary is a body of water with fresh and salt water.The most important brackish water habitats are estuaries, where a river meets the sea. The River [[Thames]] flowing through [[London]] is one of the most familiar of river estuaries. The town of [[Teddington]] a few miles west of London marks the limit of the tidal part of the Thames, although it is still a freshwater river about as far east as [[Battersea]] insofar as the average salinity is very low and the fish fauna consists predominantly of freshwater species such as [[roach]], [[dace]], [[carp]], [[perch]], and [[pike (fish)|pike]]. The Thames Estuary becomes truly brackish between Battersea and [[Gravesend, Kent|Gravesend]], and the diversity of freshwater fish species present is smaller, primarily roach and dace, [[euryhaline]] marine species such as [[flounder]], [[European seabass]], [[mullet (fish)|mullet]], and [[smelt]] become much more common. Further east, the salinity increases and the freshwater fish species are completely replaced by euryhaline marine ones, until the river reaches Gravesend, at which point conditions become fully marine and the fish fauna resembles that of the adjacent [[North Sea]] and includes both euryhaline and [[stenohaline]] marine species. A similar pattern of replacement can be observed with the aquatic plants and invertebrates living in the river [http://www.the-river-thames.co.uk/thames.htm], [http://www.the-river-thames.co.uk/wildlife.htm]. This type of [[ecological succession]] from a freshwater to marine [[ecosystem]] is typical of river estuaries. River estuaries form important staging points during the migration of [[Fish migration|anadromous and catadromus]] fish species, such as [[salmon]] and [[eel]]s, giving them time to form social groups and to adjust to the changes in salinity. Salmon are anadromous, meaning they live in the sea but ascend rivers to spawn; eels are catadromous, living in rivers and streams, but returning to the sea to breed. Besides the species that migrate through estuaries, there are many other fish that use them as "nursery grounds" for spawning or as places young fish can feed and grow before moving elsewhere. [[Herring]] and [[plaice]] are two commercially important species that use the Thames Estuary for this purpose. Estuaries are also used as fishing grounds and as places for fish farming or ranching. [[Atlantic salmon]] farms are often located in estuaries, for example, though this has caused controversy because in doing so, fish farmers expose migrating wild fish to large numbers of external [[parasites]] such as [[sea lice]] that escape from the pens the farmed fish are kept in [http://www.saveourseatrout.com/]. ===Mangroves=== Another important brackish water habitat is the [[mangrove swamp]] or '''mangal'''. Many, though not all, mangrove swamps fringe estuaries and lagoons where the salinity changes with each tide. Among the most specialised residents of mangrove forests are [[mudskippers]], fish that forage for food on land, and [[archer fish]], perch-like fish that "spit" at insects and other small animals living in the trees, knocking them into the water where they can be eaten. Like estuaries, mangrove swamps are extremely important breeding grounds for many fish, with species such as [[snapper]]s, [[halfbeak]]s, and [[tarpon]] spawning or maturing among them. Besides fish, numerous other animals use mangroves, including such specialists as the [[American crocodile]], [[proboscis monkey]], [[diamondback terrapin]], and the [[Crab-eating frog]], ''Fejervarya cancrivora formerly Rana cancrivora''. Although often plagued with [[mosquitoes]] and other insects that make them unpleasant places to visit, mangrove swamps are very important buffer zones between land and sea, and are a natural defense against hurricane and tsunami damage in particular [http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=1823&language=1]. ===Brackish seas and lakes=== Some seas and lakes are brackish. The [[Baltic Sea]] is a brackish sea adjoining the [[North Sea]]. Originally the [[confluence]] of two major river systems prior to the [[Pleistocene]], since that it has been flooded by the North Sea but still receives so much freshwater from the adjacent lands that the water is brackish. Because the salt water coming in from the sea is more dense than freshwater, the water in the Baltic is stratified, with salt water at the bottom and freshwater at the top. Limited mixing occurs because of the lack of tides and storms, with the result that the fish fauna at the surface is freshwater in composition while that lower down is more marine. [[Cod]] are an example of a species only found in deep water in the Baltic, while pike are confined to the less saline surface waters [http://www.internat.naturvardsverket.se/index.php3?main=/documents/nature/nacatego/marine/marine.htm]. The [[Caspian Sea]] is the world's largest lake and contains brackish water with a salinity about one-third that of normal seawater. The Caspian is famous for its peculiar animal fauna, including one of the few non-marine seals (the [[Caspian seal]]) and the great [[sturgeon]]s, a major source of [[caviar]]. In the [[Black sea]] the surface water is brackish with an average salinity of about 18 parts per thousand compared to 30 to 40 for the oceans. The deep, [[anoxic event|anoxic]] water of Black sea originates from warm, salty water of the [[Mediterranean]] ==Notable brackish bodies of water (by type, in alphabetical order)== '''Brackish seas''' *[[Baltic Sea]] (the world’s largest pool of brackish water) *[[Black Sea]] *[[Caspian Sea]] (world’s largest lake) '''Brackish water lakes''' [[Image:Chilka lake.png|right|thumb|200px|Map of [[lake Chilka]]. It is [[India]]'s largest lake and classified as brackish water body.]] *[[Lake Charles (Louisiana)|Lake Charles]] in [[Lake Charles, Louisiana|Lake Charles]], [[Louisiana]], [[United States|U.S.]] *[[Chilka Lake]], in [[Orissa]] state, [[India]] *[[Lake Maracaibo]], in [[Zulia]] state, [[Venezuela]] *[[Lake Monroe (Florida)|Lake Monroe]] in [[Florida]], U.S. *[[Pangong Tso]] in [[Ladakh]], [[Jammu and Kashmir]] state, [[Pakistan]] *[[Lake Van]] '''Coastal lagoons, marshes, and deltas''' *The [[Burgas Lakes]] near the [[Bulgarian Black Sea Coast]] *The [[The Fleet|Fleet]] [[lagoon]], [[Dorset]], [[England]] *[[Kaliveli Lake]], near [[Pondichery]], [[India]] *[[Kerala Backwaters]], Series of lagoons and lakes in Kerala *[[Lagos Lagoon]] in Lagos, Nigeria *[[Lake Pontchartrain]], north of [[New Orleans, Louisiana|New Orleans]], [[Louisiana]], [[United States|U.S.]] *[[Pulicat Lake]], north of [[Chennai]], [[India]] *The [[Rann of Kutch]], on the border of [[India]] and [[Pakistan]] *Parts of the [[Rhône River|Rhône]] Delta, [[France]]: An area known as the [[Camargue]] *[[Widewater]], and [[land-locked]] [[lagoon]] near [[Lancing]], [[England]] '''Estuaries''' *[[Amazon River]], empties so much freshwater into the [[Atlantic Ocean]] that it reduces the salinity of the sea for hundreds of miles *[[Chesapeake Bay]], in [[Maryland]], [[United States|U.S.]] *[[Delaware Bay]], an extension of the [[Delaware River]] in [[New Jersey]] and [[Delaware]], USA *[[Hampton Roads]], [[Virginia]], USA *Lower [[Hudson River]], in [[New York]] and [[New Jersey]], [[United States|U.S.]] *[[Lingding Yang]], [[Guangdong]], the [[People's Republic of China]] *[[Port Royal Sound]] part of Beaufort County, [[South Carolina]], USA [http://www.lowcountryestuarium.org] *[[Saint Lawrence River|Saint Lawrence]] and [[Saguenay River|Saguenay]] Rivers, the part downstream from [[Quebec City|Québec]] and [[Saguenay, Quebec|Saguenay]] respectively *[[San Francisco Bay]] and [[San Pablo Bay]] adjacent to [[San Francisco]] in [[California]], [[U.S.]] *The [[Thames Estuary]] in South East [[England]] ==See also== *[[Biosalinity]] *[[Brackish water aquarium]] *[[Desalination]] *[[Permian Sea]] *[[Slough (wetland)|Slough]] [[Category:Liquid water]] [[Category:Aquatic ecology]] [[ar:ماء مسوس]] [[cs:Brakická voda]] [[da:Brakvand]] [[de:Brackwasser]] [[et:Riimvesi]] [[es:Agua salobre]] [[eo:Saleta akvo]] [[fr:Saumâtre]] [[id:Air payau]] [[is:Ísalt]] [[he:מים מליחים]] [[nl:Brakwater]] [[ja:汽水域]] [[no:Brakkvann]] [[nn:Brakkvatn]] [[nds:Brackwater]] [[pl:Woda brachiczna]] [[pt:Água salobra]] [[simple:Brackish water]] [[sk:Brakická voda]] [[sl:Somornica]] [[fi:Murtovesi]] [[sv:Bräckt vatten]] [[zh:汽水 (水域)]]