Human population growth and rising sea levels have led to dramatic changes in ecosystems at the land-water interface. Forests have been replaced with housing, agriculture, and industries that increase nutrient, sediment, and contaminant loads to adjacent waters.
Amazon estuary The word "estuary" is derived from the Latin word aestuarium meaning tidal inlet of the sea, which in itself is derived from the term aestus, meaning tide. There have been many definitions proposed to describe an estuary. The most widely accepted definition is: A more comprehensive definition of an estuary is "a semi-enclosed body of water connected to the sea as far as the tidal limit or the salt intrusion limit and receiving freshwater runoff; however the freshwater inflow may not be perennial, the connection to the sea may be closed for part of the year and tidal influence may be negligible".
An estuary is a dynamic ecosystem having a connection to the open sea through which the sea water enters with the rhythm of the tides. The sea water entering the estuary is diluted by the fresh water flowing from rivers and streams.
The pattern of dilution varies between different estuaries and depends on the volume of fresh water, the tidal range, and the extent of evaporation of the water in the estuary. Ria Drowned river valleys are also known as coastal plain estuaries. In places where the sea level is rising relative to the land, sea water progressively penetrates into river valleys and the topography of the estuary remains similar to that of a river valley.
This is the most common type of estuary in temperate climates.
The width-to-depth ratio of these estuaries is typically large, appearing wedge-shaped in cross-section in the inner part and broadening and deepening seaward.
Examples of this type of estuary in the U. They are relatively common in tropical and subtropical locations. These estuaries are semi-isolated from ocean waters by barrier beaches barrier islands and barrier spits. Formation of barrier beaches partially encloses the estuary, with only narrow inlets allowing contact with the ocean waters.
Bar-built estuaries typically develop on gently sloping plains located along tectonically stable edges of continents and marginal sea coasts. They are extensive along the Atlantic and Gulf coasts of the U. The barrier beaches that enclose bar-built estuaries have been developed in several ways: Barrier beaches form in shallow water and are generally parallel to the shoreline, resulting in long, narrow estuaries.
Fjord-type[ edit ] Fjords were formed where pleistocene glaciers deepened and widened existing river valleys so that they become U-shaped in cross sections.
At their mouths there are typically rocks, bars or sills of glacial depositswhich have the effects of modifying the estuarine circulation.
Fjord -type estuaries are formed in deeply eroded valleys formed by glaciers. These U-shaped estuaries typically have steep sides, rock bottoms, and underwater sills contoured by glacial movement.
The estuary is shallowest at its mouth, where terminal glacial moraines or rock bars form sills that restrict water flow.
The width-to-depth ratio is generally small. In estuaries with very shallow sills, tidal oscillations only affect the water down to the depth of the sill, and the waters deeper than that may remain stagnant for a very long time, so there is only an occasional exchange of the deep water of the estuary with the ocean.
If the sill depth is deep, water circulation is less restricted, and there is a slow but steady exchange of water between the estuary and the ocean.Research of Dr. Rodney Rountree, a marine biologist specializing in ichthyology.
Research topics include marine biology, estuarine ecology, schooling behavior, soniferous behavior of fishes, fish food habits, fish sounds, bioacoustics, and various fisheries issues.
Mandela University Estuarine Ecology. likes. We are NMMU postgraduate students under the supervision of Professor Janine Adams. We specialise on 5/5(2).
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.  Estuaries form a transition zone between river environments and maritime environments.
Estuarine ecosystems are a key transition zone between freshwater and marine ecosystems, with particular importance to salmon recovery. The Watershed Program's estuarine research efforts range from basic food web research in the pelagic zone of Puget Sound to researching salmon and forage fish ecology in estuaries.
Estuarine Ecology, Second Edition, covers the physical and chemical aspects of estuaries, the biology and ecology of key organisms, the flow of organic matter through estuaries, and human interactions, such as the. The Marine & Estuarine Ecology Lab at SERC studies interactions among species and the ways that individual animals, communities and ecosystems respond to changes in the environment.