NOAA's National Ocean Service Education: Estuaries
Dec 16, From a physicist's point of view, the density difference between fresh and salt When river water meets sea water, the lighter fresh water rises up and N.Y. The Algonquin Indians called the river Mohicanituk, “the river that. Short answer: When fresh water meets salt water and they mix, the result The process of converting salt water to fresh water is called desalination and there is . Water with lower salinity is called brackish water, while where a body of salt water meets a body of freshwater (i.e. a river to the ocean) is called an estuary. Anonymous · 1 An estuary is the place where they meet. If they mix.
The continual bottom flow provides an effective ventilation system, drawing in new oceanic water and expelling brackish water. This circulation system leads to incredible ecological productivity. Nutrients and dissolved oxygen are continually resupplied from the ocean, and wastes are expelled in the surface waters. This teeming population of plankton provides a base for diverse and valuable food webs, fueling the growth of some of our most prized fish, birds, and mammals—salmon, striped bass, great blue heron, bald eagles, seals, and otters, to name a few.
The vigor of the circulation depends in part on the supply of river water to push the salt water back.
- The transition from salt to fresh water is turbulent, vulnerable, and incredibly bountiful
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- Classifying Estuaries - By Water Circulation
The San Francisco Bay area has become a center of controversy in recent years because there are many interests competing for the fresh water flowing into the Bay—principally agriculture and urban water supplies extending to Southern California.
Estuarine circulation is also affected by the tides; stronger tides generally enhance the exchange and improve the ecological function of the system. The Hudson estuary, for example, is tidal for miles inland to Troy, N. Some are self-inflicted; some are caused by the abuses of human habitation. An estuary, with all of its dynamic stirrings, has one attribute that promotes its own destruction: When suspended mud and solids from a river enter the estuary, they encounter the salt front.
Unlike fresh water, which rides up and over the saline layer, the sediment falls out of the surface layer into the denser, saltier layer of water moving into the estuary. As it drops, it gets trapped and accumulates on the bottom. Slowly, the estuary grows muddier and muddier, shallower and shallower. Occasionally a major flood will push the salt right out of the estuary, carrying the muddy sediment along with it. Sediment cores in the Hudson River indicate that sediment may accumulate for 10, 20, or even 50 years, laying down layers every year like tree rings.
But then a hurricane or big snowmelt floods the river, wipes out the layers of sediment, and sends the mud out to sea. It is good because a big storm can keep an estuary from getting too shallow too fast. In fact, it appears that over the last 6, years, the natural dredging by large storms has maintained nearly constant water depth in the Hudson estuary. Environmental regulations are far stricter now than they were 50 years ago, and we have stopped using many chemicals that play havoc with the environment.
For instance, polychlorinated biphenyls PCBs were banned in the s because they were shown to be toxic to fish and wildlife, and to the humans who consume them.
What is an Estuary? The Areas Where Fresh & Salt Water Meet Are Known As Estuaries
Trickle-down effects Billions of dollars are now being spent to clean up American estuaries contaminated by industrial pollution. The Superfund program of the U. Environmental Protection Agency collects and spends billions of dollars more to remediate estuaries. Often the remediation strategies are complex and controversial.
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 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. 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.
A semi-enclosed coastal body of water which has a free connection with the open sea.
The seawater is usually measurably diluted with freshwater. A place where fresh and salt water mix, such as a bay, salt marsh, or where a river enters an ocean. Semi-enclosed body of water that has a free connection with open seas and within which the seawater is measurably diluted with fresh water derived from land drainage.
What is it called when fresh water meets salt water?
The salinity of an estuary exceeds 0. Partially enclosed body of water where fresh water from rivers and streams mixes with salt water from the ocean. It is an area of transition from land to sea.
Formation of water resulting from the discharge of low-salinity water into marine waters of the ocean, forming a distinct layer of water on top of the seawater due to its lower density.