An estuary is a partly enclosed coastal The coast is defined as where the land meets the sea. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs. Both the terms coast and coastal are often used to body of water Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state, water vapor or steam with one or more rivers A river is a natural watercourse, usually freshwater, flowing toward an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and rill; there is no or streams A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, crick, kill, lick, rill, river syke, bayou, rivulet, streamage, wash, run or runnel. In some countries or communities a stream may be defined by flowing into it, and with a free connection to the open sea A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, the term refers to a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean. It is also used sometimes to describe a large saline lake that lacks a natural outlet, such as the Caspian Sea.[1]

Estuaries form a transition zone between river environments and ocean environments and are subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment. The inflow of both seawater and freshwater provide high levels of nutrients in both the water column and sediment, making estuaries among the most productive natural habitats in the world [2]

Most modern-day estuaries were formed during the Holocene The Holocene is a geological epoch which began approximately 12,000 years ago . According to traditional geological thinking, the Holocene continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words ὅλος (holos, whole or entire) and καινός (kainos, new), meaning "entirely recent" epoch by the flooding of river-eroded or glacially-scoured valleys when sea level began to rise about 10,000-12,000 years ago.[3] Estuaries are typically classified by their geomorphological features or by water circulation patterns and can be referred to by many different names, such as bays, harbors, lagoons, inlets, or sounds, although sometimes these water bodies do not necessarily meet the above criteria of an estuary and may be fully saline.

Estuaries are amongst the most heavily populated areas throughout the world, with about 60% of the world’s population living along estuaries and the coast. As a result, estuaries are suffering degradation by many factors, including sedimentation from soil erosion from deforestation; overgrazing and other poor farming practices; overfishing; drainage and filling of wetlands; eutrophication due to excessive nutrients from sewage and animal wastes; pollutants including heavy metals, PCBs, radionuclides and hydrocarbons from sewage inputs; and diking or damming for flood control or water diversion.[3]

River Exe estuary River Nith estuary Estuary mouth located in Darwin Darwin is the capital city of the Northern Territory, Australia. Situated on the Timor Sea, Darwin has a population of 124,800, making it by far the largest and most populated city in the sparsely populated Northern Territory, but the least populous of all Australia's capital cities. It is the smallest and most northerly of the Australian capital, Northern Territory The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions. It shares borders with Western Australia to the west , South Australia to the south (26th parallel south), and Queensland to the east (138th meridian east), Australia For at least 40,000 years before European settlement in the late 18th century, Australia was inhabited by indigenous Australians, who belonged to one or more of the roughly 250 language groups. After sporadic visits by fishermen from the immediate north and discovery by Dutch explorers in 1606, Australia's eastern half was claimed by the British Estuary mouth Río de la Plata The Río de la Plata – always rendered River Plate in British English and the Commonwealth, and occasionally rendered [La] Plata River in other English-speaking countries – is the river formed by the combination of the Uruguay River and the Paraná River. It is a funnel-shaped indentation on the southeastern coastline of South America, estuary Estuary mouth of the Yachats River in Yachats, Oregon Amazon The Amazon River (Portuguese: Rio Amazonas; Spanish: Río Amazonas; pronounced /ˈæməzɒn/ ; /ˈæməzən/ (UK)) of South America is the largest river in the world with a total river flow greater than the next ten largest rivers combined. The Amazon, which has the largest drainage basin in the world, accounts for approximately one-fifth of the estuary

Contents

Definition of an 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 semi-enclosed coastal body of water, which has a free connection with the open sea, and within which sea water is measurably diluted with freshwater derived from land drainage.” [1] However, this definition excludes a number of coastal water bodies such as coastal lagoons and brackish seas. A more thorough definition of an estuary would be “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.” [3] This definition includes classical estuaries as well as fjords Geologically, a fjord (pronounced /ˈfjɔrd/ or /ˈfiː.ɔrd/) is a long, narrow inlet with steep sides, created in a valley carved by glacial activity, lagoons A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier, river mouths, and tidal creeks. Estuaries are a dynamic ecosystem An ecosystem consists of all the organisms living in a particular area, as well as all the nonliving, physical components of the environment with which the organisms interact, such as air, soil, water, and sunlight. It is all the organisms in a given area, along with the nonliving factors with which they interact; a biological community and its with a connection with the open sea through which the seawater Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every kilogram, or every litre, of seawater has approximately 35 grams of dissolved salts (mostly, but not entirely, the ions of sodium chloride: Na+, Cl−). The average density of seawater at the ocean surface is 1.025 enters accordingly to the rhythm of the tides Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. The tides occur with a period of approximately 12 hours and 25 minutes, and with an amplitude that is influenced by the alignment of the sun and moon and the shape of the near-shore. The seawater entering the estuary is diluted by the freshwater Freshwater or fresh water is naturally occurring water on the Earth's surface in bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Freshwater is characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludes seawater and flowing from rivers and streams. The pattern of dilution varies in different estuaries and is dependent on the volume of freshwater, tidal amplitude range, and the extent of evaporation from the water within the estuary. [2]

Classification of estuaries

Estuaries have been classified according to many different schemes. Most commonly, estuaries are classified according to their geomorphology Geomorphology is the scientific study of landforms and the processes that shape them. Geomorphologists seek to understand why landscapes look the way they do: to understand landform history and dynamics, and predict future changes through a combination of field observation, physical experiment, and numerical modeling. Geomorphology is practiced or water circulation.

Classification based on geomorphology

Drowned river valleys

Many drowned river valley estuaries were formed between about 15,000 and 6000 years ago following the end of the Wisconsin (or 'Devensian') glaciation The last glacial period was the most recent glacial period within the current ice age occurring during the Pleistocene from ~110,000—10,000 years ago, a period of ~0.1 million years when a eustatic Mean sea level is a measure of the average height of the ocean's surface (such as the halfway point between between the mean high tide and the mean low tide); used as a standard in reckoning land elevation rise in sea level Mean sea level is a measure of the average height of the ocean's surface (such as the halfway point between the mean high tide and the mean low tide); used as a standard in reckoning land elevation of 100 m to 130 m, flooded river valleys that were cut into the landscape when sea level was lower, creating the estuarine systems. Additionally, the general subsidence Subsidence is the motion of a surface as it shifts downward relative to a datum such as sea-level. The opposite of subsidence is uplift, which results in an increase in elevation. Ground subsidence is of concern to geologists, structural engineers and surveyors of coastal regions contributed to the development of drowned river valleys. Well developed drowned river valleys are generally found on coastlines with low, wide coastal plains A coastal plain is an area of flat, low-lying land adjacent to a seacoast and separated from the interior by other features. One of the world's longest coastal plains is located in western South America. The southwestern coastal plain of North America is notable for its species diversity. The Gulf Coastal Plain of North America extends northwards. Their width-to-depth ratio is typically large, appearing wedge-shaped in the inner part and broadening and deepening seaward. Water depths rarely exceed 30 meters. Examples of this type of estuary include the Chesapeake Bay The Chesapeake Bay is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Maryland and Virginia. The Chesapeake Bay's drainage basin covers 64,299 square miles (166,534 km2) in the District of Columbia and parts of six states: New York, Pennsylvania, Delaware, Maryland, Virginia, and West Virginia. More than 150 and Delaware Bay Delaware Bay is a major estuary outlet of the Delaware River on the Northeast seaboard of the United States whose fresh water mixes for many miles with the waters of the Atlantic Ocean. It is 782 square miles in area. The bay is bordered by the State of New Jersey and the State of Delaware. It was the first site classified in the Western, along the U.S. mid-Atlantic coast, and along the U.S. Gulf coast The Gulf Coast of the United States, sometimes referred to as the Gulf South or South Coast, comprises the coasts of American states that are on the Gulf of Mexico. These states are Texas, Louisiana, Mississippi, Alabama, and Florida and are known as the Gulf States. All Gulf States are located in the Southern region of the United States, Galveston Bay The bay has been historically important during Texas' history. The island of Galveston was home to eastern and coastal Texas' earliest major settlement and, during the later 19th century, it was Texas' largest city. The island's port, on the bay side, became one of the top ports in the U.S. During the 20th century as the oil boom in Texas took and Tampa Bay Tampa Bay is a large natural harbor and estuary along the Gulf of Mexico on the west central coast of Florida, comprising Hillsborough Bay, Old Tampa Bay, Middle Tampa Bay, and Lower Tampa Bay[4].

Lagoon-type or bar-built estuaries

These estuaries are semi-isolated from ocean waters by barrier beaches (barrier islands Barrier islands, a coastal landform and a type of barrier system, are relatively narrow strips of sand that parallel the mainland coast. They usually occur in chains, consisting of a few islands or more than a dozen. Excepting the tidal inlets that separate the islands, a barrier chain may extend uninterrupted for over a hundred kilometers. The and barrier spits A spit or sandspit is a deposition landform found off coasts. At one end, spits connect to land, while at the far end they exist in open water. A spit is a type of bar or beach that develops where a re-entrant occurs, such as at cove's headlands, by the process of longshore drift. Longshore drift occurs due to waves meeting the beach at an oblique). 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.S. in areas with active coastal deposition of sediments and where tidal ranges are less than 4 meters. The barrier beaches that enclose bar-built estuaries have been developed in several ways: 1) upbuilding of offshore bars from wave action, in which sand from the seafloor is deposited in elongate bars parallel to the shoreline, 2) reworking of sediment discharge from rivers by wave, current, and wind action into beaches, overwash flats, and dunes, 3) engulfment of mainland beach ridges (ridges developed from the erosion of coastal plain sediments approximately 5,000 years ago) due to sea level rise and resulting in the breaching of the ridges and flooding of the coastal lowlands, forming shallow lagoons, 4) elongation of barrier spits from the erosion of headlands, with the spit growth occurring in the direction of the littoral drift due to the action of longshore currents. Barrier beaches form in shallow water and are generally parallel to the shoreline, resulting in long, narrow estuaries. The average water depth is usually less than 5 m, and rarely exceed 10 m. Examples of bar-built estuaries include Barnegat Bay Barnegat Bay is a small brackish arm of the Atlantic Ocean, approximately 30 miles long, along the coast of Ocean County, New Jersey in the United States. It is essentially a long estuary formed by Barnegat Peninsula, a long barrier peninsula, as well as by the north end of Long Beach Island. The bay is fed by several small rivers, including the, New Jersey The area was inhabited by Native Americans for more than 2,800 years, with historical tribes such as the Lenape along the coast. In the early 1600s, the Dutch and the Swedes made the first European settlements. The English later seized control of the region, naming it the Province of New Jersey. It was granted as a colony to Sir George Carteret, Laguna Madre The Laguna Madre is a long shallow hypersaline bay along the western coast of the Gulf of Mexico in Nueces, Kenedy, Kleberg, Willacy and Cameron counties in Texas, United States. It is separated by the roughly 20-mile long Saltillo Flats land bridge into Upper and Lower bays. The two are joined by the Intracoastal Waterway, which has been dredged, Texas Houston is the largest city in Texas and the fourth-largest in the United States, while San Antonio is the second largest in the state and seventh largest in the United States. Dallas–Fort Worth and Greater Houston are the fourth and sixth largest United States metropolitan areas, respectively. Other major cities include El Paso and Austin—the, and Pamlico Sound Pamlico Sound in North Carolina, is the largest lagoon along the U.S. East Coast, being 129 km (80 miles) long and 24 to 48 km (15 to 30 miles) wide. It is a body of water separated from the Atlantic Ocean by the Outer Banks, a row of low, sandy barrier islands, including Cape Hatteras. The Neuse and Pamlico rivers (the latter is the estuary of, North Carolina Spanish colonial forces were the first Europeans to make a permanent settlement in the area, when the Juan Pardo-led Expedition built Fort San Juan in 1567. This was sited at Joara, a Mississippian culture regional chiefdom near present-day Morganton in the western interior. This was 20 years before the English established their first colony at.

Fjord-type estuaries

Fjord Geologically, a fjord (pronounced /ˈfjɔrd/ or /ˈfiː.ɔrd/) is a long, narrow inlet with steep sides, created in a valley carved by glacial activity type estuaries are formed in deeply eroded valleys formed by glaciers A glacier is a perennial mass of ice which moves over land. A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years. The word glacier comes from French via the Vulgar Latin glacia, and ultimately from Latin glacies meaning ice. The corresponding area of study is called glaciology. These U-shaped estuaries typically have steep sides, rock bottoms, and underwater sills contoured by glacial movement. The shallowest area of the estuary occurs at the mouth, where terminal glacial deposits or rock bars form sills that restrict water flow. In the upper reaches of the estuary, the depth can exceed 300 meters. The width-to-depth ratio is generally small. When estuaries contain very shallow sills, tidal oscillations only affect near surface waters to sill depth, and waters below sill depth may remain stagnant for very long periods of time, resulting in 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 a slow, but steady exchange of water from the estuary and the ocean occur. Fjord-type estuaries can be found along the coasts of Alaska Alaska was purchased from the Russian Empire on March 30, 1867, for $7.2 million at about two cents per acre . The land went through several administrative changes before becoming an organized territory on May 11, 1912, and the 49th state of the U.S. on January 3, 1959, eastern Canada The land occupied by Canada was inhabited for millennia by various groups of Aboriginal peoples. Beginning in the late 15th century, British and French expeditions explored, and later settled, along the Atlantic coast. France ceded nearly all of its colonies in North America in 1763 after the Seven Years' War. In 1867, with the union of three, Greenland b. ^ Greenland, the Faeroes and Iceland were formally Norwegian possessions until 1814 despite 400 years of Danish monarchy beforehand, Iceland b. ^ Iceland, the Faeroes and Greenland were formally Norwegian possessions until 1814 despite 400 years of Danish monarchy beforehand, New Zealand New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori language name for New Zealand is Aotearoa, commonly translated as The Land of the Long White Cloud. The Realm of New Zealand also, and Norway After World War II, Norway experienced rapid economic growth, with the first two decades due to the Norwegian shipping and merchant marine and domestic industrialization, and from the early 1970s, a result of exploiting large oil and natural gas deposits that had been discovered in the North Sea and the Norwegian Sea. Today, Norway ranks as the.

Tectonically produced estuaries

These estuaries are formed by subsidence or land cut off from the ocean by land movement associated with faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement. Large faults within the Earth's crust result from the action of tectonic forces. Energy release associated with rapid movement on active faults is the cause of most earthquakes, volcanoes A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, ash and gases to escape from below the surface, and landslides A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing. Inundation A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, from eustatic sea level rise during the Holocene The Holocene is a geological epoch which began approximately 12,000 years ago . According to traditional geological thinking, the Holocene continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words ὅλος (holos, whole or entire) and καινός (kainos, new), meaning "entirely recent" Epoch An epoch is in geology a division of the geologic timescale. Epochs are subdivisions of periods and are themselves subdivided into ages has also contributed to the formation of these estuaries. There are only a small number of tectonically produced estuaries; one example is the San Francisco Bay, which was formed by the crustal movements of the San Andreas fault system causing the inundation of the lower reaches of the Sacramento and San Joaquin rivers.[5]

Classification based on water circulation

Salt wedge estuaries

In this type of estuary, river output greatly exceeds marine input and tidal effects have a minor importance. Fresh water floats on top of the seawater in a layer that gradually thins as it moves seaward. The denser seawater moves landward along the bottom of the estuary, forming a wedge-shaped layer that is thinner as it approaches land. As a velocity difference develops between the two layers, shear forces generate internal waves at the interface, mixing the seawater upward with the freshwater. An example of a salt wedge estuary is the Mississippi River. [5]

Partially mixed estuaries

As tidal forcing increases, river output becomes less than the marine input. Here, current induced turbulence causes mixing of the whole water column such that salinity varies more longitudinally rather than vertically, leading to a moderately stratified condition. Examples include the Chesapeake Bay and Narragansett Bay. [5]

Vertically homogenous estuaries

Tidal mixing forces exceed river output, resulting in a well mixed water column and the disappearance of the vertical salinity gradient. The freshwater-seawater boundary is eliminated due to the intense turbulent mixing and eddy effects. The lower reaches of the Delaware Bay and the Raritan River in New Jersey are examples of vertically homogenous estuaries. [5]

Inverse estuary

Inverse estuaries occur in dry climates where evaporation greatly exceeds the inflow of fresh water. A salinity maximum zone is formed, and both riverine and oceanic water flow close to the surface towards this zone.[6] This water is pushed downward and spreads along the bottom in both the seaward and landward direction. [3] An example of an inverse estuary is Spencer Gulf, South Australia.

Intermittent estuaries

Estuary type varies dramatically depending on freshwater input, and is capable of changing from a wholly marine embayment to any of the other estuary types. [7] [8]

(See also Estuarine water circulation)

Implications for marine life

Estuaries provide habitats for a large number of organisms and support very high productivity. Estuaries provide habitats for many fish nurseries, depending upon their locations in the world, such as salmon and sea trout[9]. Also, migratory bird populations, such as the black-tailed godwit, Limosa limosa islandica[10] make essential use of estuaries.

Two of the main challenges of estuarine life are the variability in salinity and sedimentation. Many species of fish and invertebrates have various methods to control or conform to the shifts in salt concentrations and are termed osmoconformers and osmoregulators. Many animals also burrow to avoid predation and to live in the more stable sedimental environment. However, large numbers of bacteria are found within the sediment which have a very high oxygen demand. This reduces the levels of oxygen within the sediment often resulting in partially anoxic conditions, which can be further exacerbated by limited water flux.

Plankton are key primary producers in estuaries. They move with the water bodies and can be flushed in and out with the tides. Their productivity is largely dependant upon the turbidity of the water. The main plankton present are diatoms and dinoflagellates which are abundant in the sediment.

It is important to remember that a primary source of food for many organisms on estuaries, including bacteria, is detritus from the settlement of the sedimentation.

Human impacts

Of the 32 largest cities in the world, 22 are located on estuaries.[11] For example, New York City is located at the orifice of the Hudson River estuary.[12]

As ecosystems, estuaries are under threat from human activities such as pollution and overfishing. They are also threatened by sewage, coastal settlement, land clearance and much more. Estuaries are affected by events far upstream, and concentrate materials such as pollutants and sediments[13]. Land run-off and industrial, agricultural, and domestic waste enter rivers and are discharged into estuaries. Contaminants can be introduced which do not disintegrate rapidly in the marine environment, such as plastics, pesticides, furans, dioxins, phenols and heavy metals.

Such toxins can accumulate in the tissues of many species of aquatic life in a process called bioaccumulation. They also accumulate in benthic environments, such as estuaries and bay muds: a geological record of human activities of the last century.

For example, Chinese and Russian industrial pollution, such as phenols and heavy metals, in the Amur River have devastated fish stocks and damaged its estuary soil.[14]

Estuaries tend to be naturally eutrophic because land runoff discharges nutrients into estuaries. With human activities, land run-off also now includes the many chemicals used as fertilizers in agriculture as well as waste from livestock and humans. Excess oxygen depleting chemicals in the water can lead to hypoxia and the creation of dead zones.[15] It can result in reductions in water quality, fish, and other animal populations.

Overfishing also occurs. Chesapeake Bay once had a flourishing oyster population which has been almost wiped out by overfishing. Historically the oysters filtered the estuary's entire water volume of excess nutrients every three or four days. Today that process takes almost a year,[16] and sediment, nutrients, and algae can cause problems in local waters. Oysters filter these pollutants, and either eat them or shape them into small packets that are deposited on the bottom where they are harmless.

Notable examples

See also

Water portal
Environment portal

References

  1. ^ a b Pritchard, D. W. (1967) What is an estuary: physical viewpoint. p. 3–5 in: G. H. Lauf (ed.) Estuaries, A.A.A.S. Publ. No. 83, Washington, D.C.
  2. ^ a b McLusky, D.S. and Elliott, M. (2004) "The Estuarine Ecosystem: ecology, threats and management." New York: Oxford University Press Inc. ISBN 0-19-852508-7
  3. ^ a b c d Wolanski, E. (2007) "Estuarine Ecohydrology." Amsterdam, The Netherlands: Elsevier. ISBN 978-0-444-53066-0
  4. ^ Kunneke, J.T., and T.F. Palik, 1984. "Tampa Bay environmental atlas", U.S. Fish Wildl. Serv. Biol. Rep. 85(15), page 3. Retrieved January 12, 2010.
  5. ^ a b c d Kennish, M.J. (1986) "Ecology of Estuaries. Volume I: Physical and Chemical Aspects." Boca Raton, FL: CRC Press, Inc. ISBN: 0-8493-5892-2
  6. ^ Wolanski, E. (1986). "An evaporation-driven salinity maximum zone in Australian tropical estuaries" Estuarine, Coastal, and Shelf Science 22, 415-424.
  7. ^ Tomczak, M (2000) "Oceanography Notes Ch. 12: Estuaries. Retrieved 30 November 2006.
  8. ^ Day, J.H. (1981) "Estuarine Ecology." Rotterdam, The Netherlands: A.A. Balkema. ISBN: 90-6191-205-9.
  9. ^ Bronwyn M. Gillanders, Evidence of connectivity between juvenile and adult habitats for mobile marine fauna: an important component of nurseries. 2003. Marine Ecology Progress Series
  10. ^ Jennifer A. Gill, The buffer effect and large-scale population regulation in migratory birds. 2001. Nature 412, 436-438
  11. ^ Ross, D A (1995) Introduction to Oceanography. New York: Harper Collins College Publishers. ISBN 978-0-673-46938-0
  12. ^ NOAA Estuaries tutorial Revised March 25, 2008
  13. ^ G.Branch, Estuarine vulnerability and ecological impacts, TREE vol. 14, no. 12 Dec. 1999
  14. ^ "Indigenous Peoples of the Russian North, Siberia and Far East: Nivkh" by Arctic Network for the Support of the Indigenous Peoples of the Russian Arctic]
  15. ^ Gerlach: Marine Pollution, Springer, Berlin (1975)
  16. ^ "Oyster Reefs: Ecological importance". US National Oceanic and Atmospheric Administration. http://habitat.noaa.gov/restorationtechniques/public/habitat.cfm?HabitatID=2&HabitatTopicID=11. Retrieved 2008-01-16.

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Sat Jul 24 07:03:59 2010
'Estuary' Blogs
Dutra DC Wins Los Angeles River Estuary Dredging Contract (USA)
dredgingtoday.com
Dutra DC Wins Los Angeles River Estuary Dredging Contract (USA)

Dredging Today

Sun, 04 Jul 2010 08:13:53 GM

USACE awarded recovery project of Los Angeles . estuary. dredging at Long Beach to Dutra Dredging company. Contract award date is June 30, 2010, value of contract is $1289127.00. Modification is issued to provide all labor, equipment and ...

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Wed Jul 21 14:10:03 2010
'Estuary' Answers
How do you make an estuary experiment?
Q. i need to make an experiment for science. and it doesnt have to be particular i just need an experiment on how water mixes in an estuary. helpp?!?!?!??!
Asked by Lisa - Mon Sep 29 15:14:39 2008 - - 1 Answers - 0 Comments

A. The thing that would be interesting to make is called a halocline - a layer of freshwater on top of the (denser) saltwater (first link.) Second link below is an excerpt from a book that discusses this. I've scuba dived in a halocline - in an inland cenote (underwater cave) in Mexico. Very bizarre.
Answered by more slack - Tue Sep 30 16:54:40 2008

Yahoo Answers Search: Estuary,
Mon Jul 19 14:45:53 2010
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