When fresh water meets salty water | NIWA
Inside the natural feature named estuary, an amazing phenomenon happens continuously, which is the interaction of river fresh water and the. Brackish water is water that has more salt than freshwater, but not as much as seawater. Brackish water condition commonly occurs when fresh water meets seawater. In fact, the most extensive brackish water habitats worldwide are. It's not fresh water mixing with ocean water it's actually an outlet of a .. I mean its clearly and blatantly not salt water and fresh water meeting.
Among the most specialised residents of mangrove forests are mudskippersfish that forage for food on land, and archer fishperch-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 snappershalfbeaksand tarpon spawning or maturing among them.
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Besides fish, numerous other animals use mangroves, including such species as the saltwater crocodileAmerican crocodileproboscis monkeydiamondback terrapinand the crab-eating frogFejervarya cancrivora formerly Rana cancrivora. Mangroves represent important nesting site for numerous birds groups such as herons, storks, spoonbills, ibises, kingfishers, shorebirds and seabirds.
Although often plagued with mosquitoes and other insects that make them unpleasant for humans, mangrove swamps are very important buffer zones between land and sea, and are a natural defense against hurricane and tsunami damage in particular.
Brackish seas and lakes[ edit ] 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 Pleistocenesince then 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 denser 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.
The Caspian Sea is the world's largest lake and contains brackish water with a salinity about one-third that of normal seawater.
NOAA's National Ocean Service Education: Estuaries
The Caspian is famous for its peculiar animal fauna, including one of the few non-marine seals the Caspian seal and the great sturgeonsa major source of caviar. The Hudson Bay is a brackish marginal sea of the arctic oceanit remains brackish due its limited connections to the open ocean, very high levels freshwater surface runoff input from the large Hudson Bay drainage basinand low rate of evaporation due to being completely covered in ice for over half the year.
The five major types of estuaries classified according to their water circulation include salt-wedgefjordslightly stratifiedvertically mixedand freshwater Levinson, ; USEPA, Water movements in estuaries transport organisms, circulate nutrients and oxygen, and transport sediments and wastes.
Once or twice a day, high tides create saltwater currents that move seawater up into the estuary. Low tides, also once or twice a day, reverse these currents. In some estuaries, the mixing of fresh water from rivers and saltwater from the sea is extensive; in others it is not. In the Hudson River in New York, for example, tidal currents carry saltwater over km upstream. Fjords are typically long, narrow valleys with steep sides that were created by advancing glaciers.
Click the image for more details and to view a large animation. The daily mixing of fresh water and saltwater in estuaries leads to variable and dynamic chemical conditions, especially salinity.
When fresh water and saltwater meet in an estuary, they do not always mix very readily.
Because fresh water flowing into the estuary is less salty and less dense than water from the ocean, it often floats on top of the heavier seawater.