Marine habitats
Estuary of Klamath River in Northern California
	Littoral zone
	Intertidal zone
	Estuaries
	Kelp forests
	Coral reefs
	Ocean banks
	Continental shelf
	Neritic zone
	Straits
	Pelagic zone
	Oceanic zone
	Seamounts
	Hydrothermal vents
	Cold seeps
	Demersal zone
	Benthic zone
v t e

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open 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 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]

Definition[link]

Hudson River estuary waterways around New York City, USA: 1. Hudson River, 2. East River, 3. Long Island Sound, 4. Newark Bay, 5. Upper New York Bay, 6. Lower New York Bay, separated from Upper New York Bay by the Verrazano Narrows strait, 7. Jamaica Bay, and 8. Atlantic Ocean. River Exe estuary River Nith estuary Estuary mouth located in Darwin, Northern Territory, Australia Estuary mouth Río de la Plata estuary File:Yachats River estuary mouth.jpg Estuary mouth of the Yachats River in Yachats, Oregon 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 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, lagoons, river mouths, and tidal creeks. Estuaries are a dynamic ecosystem with a connection with the open sea through which the seawater enters accordingly to the rhythm of the tides. The seawater entering the estuary is diluted by the freshwater 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 based on geomorphology[link]

Drowned river valleys[link]

Many drowned river valley estuaries were formed between about 15,000 and 6000 years ago following the end of the Wisconsin (or 'Devensian') glaciation when a eustatic rise in sea level of 100 to 130 m (330 to 430 ft) flooded river valleys that were cut into the landscape when sea level was lower, creating the estuarine systems. Additionally, the general subsidence of coastal regions contributed to the development. Well-developed drowned river valleys are generally found on coastlines with low, wide coastal plains. 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 m (98 ft). Examples of this type of estuary include the Hudson River, Chesapeake Bay, and Delaware Bay along the U.S. Mid-Atlantic coast; and along the U.S. Gulf coast, Galveston Bay and Tampa Bay.^[4]

Lagoon-type or bar-built[link]

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.S. in areas with active coastal deposition of sediments and where tidal ranges are less than 4 m (13 ft). 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, and 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 (16 ft), and rarely exceed 10 m (33 ft). Examples of bar-built estuaries include Barnegat Bay, New Jersey, Laguna Madre, Texas, and Pamlico Sound, North Carolina.

Fjord-type[link]

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 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 m (980 ft). 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, the Puget Sound region of western Washington state, eastern Canada, Greenland, Iceland, New Zealand, and Norway.

Tectonically produced[link]

These estuaries are formed by subsidence or land cut off from the ocean by land movement associated with faulting, volcanoes, and landslides. Inundation from eustatic sea level rise during the Holocene Epoch 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[link]

Salt wedge[link]

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[link]

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[link]

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[link]

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[link]

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)

Physiochemical variation[link]

Estuary variables consist predominantly of fluctuations in dissolved oxygen, salinity and sediment load within the water. There is extreme spatial variability in salinity, with a range of near 0 at the river end to 34 ‰ at the estuary mouth. At any one point the salinity will vary considerably over time and seasons, making it a harsh environment for organisms. Sediment often settles in intertidal mudflats which are extremely difficult to colonize. No points of attachment exist for algae so vegetation based habitat is not established. Sediment can also clog feeding and respiratory structures of species, so special adaptations exist within mudflat species to cope with this problem. Lastly, dissolved oxygen variation can limit the livability of the habitat. With the impact of nutrient rich sediment from anthropogenic sources, primary production life cycles thrive and eventual decay removing the dissolved oxygen from the water, hypoxic or anoxic zones can develop.^[9]

Implications for marine life[link]

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.^[10] Also, migratory bird populations, such as the black-tailed godwit, Limosa limosa islandica^[11] 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.

Phytoplankton 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 phytoplankton 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[link]

22 of the world's largest cities are located on estuaries.^[12] For example, New York City is located at the orifice of the Hudson River estuary.^[13]

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.^[14] 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.^[15]

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.^[16] 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,^[17] 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[link]

See also[link]

	Water portal
	Environment portal

References[link]

External links[link]

Wikimedia Commons has media related to: Estuaries

Look up estuary in Wiktionary, the free dictionary.

• Animated documentary on Chesapeake Bay NOAA.
• "Habitats: Estuaries - Characteristics". www.onr.navy.mil. http://www.onr.navy.mil/Focus/ocean/habitats/estuaries1.htm. Retrieved 2009-11-17
• The Estuary Guide (Based on experience and R&D within the UK). 

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Tom Harrell
Background information
Born	(1946-06-16) June 16, 1946 (age 66)
Origin	Urbana, Illinois, U.S.
Instruments	Trumpet, Flugelhorn
Associated acts	Stan Kenton, Woody Herman, Azteca, Horace Silver, many others
Website	www.tomharrell.com

Tom Harrell (born June 16, 1946) is a renowned American post-bop jazz trumpeter, flugelhornist, composer and arranger.

Harrell has won numerous awards and grants, including multiple Trumpeter of the Year awards from Down Beat magazine,^[1][2] SESAC Jazz Award, BMI (Broadcast Music Incorporated) Composers Award, and Prix Oscar du Jazz. He also received a Grammy nomination for his big band album, Time's Mirror.

He has been recorded on over 260 albums (according to the discography on his website) and continues to actively compose, record and tour extensively around the world.^[3]

Biography[link]

Tom Harrell was born in Urbana, Illinois, but moved to the San Francisco Bay Area at the age of five. He started playing trumpet at eight and within five years, started playing gigs with local bands. In 1969 he graduated from Stanford University with a music composition degree^[4] and joined Stan Kenton's orchestra, touring and recording with them throughout 1969.

After leaving Kenton, Harrell played with Woody Herman's big band (1970–1971), Azteca (1972), the Horace Silver^[5] Quintet (1973–1977), with whom he made five albums, the Sam Jones-Tom Harrell Big Band, the Lee Konitz Nonet (1979–1981), George Russell, and the Mel Lewis Orchestra (1981). From 1983 to 1989 he was a pivotal member of the Phil Woods Quintet and made seven albums with the group. In addition, he recorded albums with Vince Guaraldi for whom he also did some arranging for the Peanuts television specials, Bill Evans, Dizzy Gillespie, Ronnie Cuber, Bob Brookmeyer, Lionel Hampton, Bob Berg, Cecil Payne, Bobby Shew, Phillipe Catherine, Ivan Paduart, Joe Lovano, Charlie Haden's Liberation Orchestra, Art Farmer, Charles McPherson, David Sánchez, Sheila Jordan, Jane Monheit, King's Singers and Kathleen Battle among others.

Harrell is a prolific arranger and composer. He has arranged for Vince Guaraldi's work on Peanuts, Carlos Santana, the Metropole Orchestra, the Danish Radio Big Band, the Vanguard Jazz Orchestra, and Elisabeth Kontomanou with the Orchestre National de Lorraine, among others. His compositions have been recorded by other notable jazz artists including Ron Carter, Joe Lovano, Kenny Barron, Art Farmer, Chris Potter, Tom Scott, Steve Kuhn, Kenny Werner and Hank Jones. Harrell's composition and big band arrangement entitled "Humility" was recorded on the Grammy-winning album by Arturo O'Farrill's Afro-Latin Jazz Orchestra, Song for Chico.

Despite his well-documented schizophrenia, Harrell has successfully coped with the condition through medication and has become an influential figure as a jazz trumpeter and composer.^[6][7]

Tom Harrell Quintet[link]

Since 1989 Harrell has led his own groups, usually quintets but occasionally expanded ensembles such as chamber orchestras with strings, and big bands. He has appeared at virtually every major jazz club and festival venue, and recorded under his own name for such record labels as RCA, Contemporary, Pinnacle, Blackhawk, Criss Cross, SteepleChase, Chesky, and HighNote.

In contrast to his signature recordings during the RCA/BMG years (1996–2003), where much of his focus was on projects involving large ensembles, big bands and chamber orchestras, Harrell's more recent works demonstrate his skills as a leader of a tight, smaller unit. Harrell has made four albums with the current quintet of six years, which comprises tenor saxophonist Wayne Escoffery, pianist Danny Grissett, bassist Ugonna Okegwo (whom Harrell has employed consistently since 1997), and drummer Johnathan Blake.^[8] The group is noted for its strong chemistry between the musicians and the distinctive sound achieved primarily through Harrell's compositions that combine memorable and accessible melodies with complex but groove-based rhythms and sophisticated harmonic textures.^[9][10] Harrell's current quintet differs from previous editions of quintets he has formed and worked with, in the use of Fender Rhodes and acoustic piano.^[11] Harrell's 2011 recording, The Time of the Sun, received his sixth SESAC Jazz Award.^[12] In May 2012, the group's latest album, Number Five, will be released on Highnote Records.^[13][14]

Harrell's work as composer and jazz soloist has been published in a number of books by Hal Leonard,^[15]Jamey Aebersold,^[16] Sher Music,^[17][18] and Gerard and Sarzin.^[19]

Harrell is currently represented by Addeo Music International (AMI).

Discography[link]

As leader[link]

• 2012 : Number Five
• 2011 : The Time of the Sun
• 2010 : Roman Nights
• 2009 : Prana Dance
• 2007 : Light On
• 2007 : Humanity
• 2003 : Wise Children
• 2002 : Live at the Village Vanguard
• 2001 : Paradise
• 1999 : Time's Mirror
• 1998 : The Art of Rhythm
• 1996 : Labyrinth
• 1995 : Cape Verde
• 1994 : Upswing
• 1992 : Visions
• 1992 : Sail Away - live in Paris
• 1991 : Form
• 1991 : Moon and Sand
• 1990 : Form
• 1989 : Sail Away
• 1989 : Lonely Eyes
• 1988 : Stories
• 1987 : Open Air
• 1986 : Sundance
• 1985 : Moon Alley
• 1984 : Play of Light
• 1979 : Look to the Sky
• 1978 : Mind's ear
• 1976 : Aurora

As sideman[link]

This section requires expansion.

With George Gruntz

• Theatre (ECM, 1983)

With Charlie Haden

• The Montreal Tapes: Liberation Music Orchestra (Verve, 1989 [1999])

With Joe Lovano

• Village Rhythm (Soul Note, 1988)
• Quartets: Live at the Village Vanguard (Blue Note, 1994)

With Horace Silver

• Silver 'n Brass (Blue Note, 1975)^[20]

With Jacky Terrasson

• Moon and Sand (Jazz aux Remparts, 1995)

With Phil Woods

• Dizzy Gillespie Meets Phil Woods Quintet (Timeless, 1986) - with Dizzy Gillespie

References[link]

External links[link]

Wikimedia Commons has media related to: Tom Harrell

• Tom Harrell Official Website
• Official Twitter page
• Tom Harrell Official Facebook Page
• Official MySpace Page
• Tom Harrell Live at The Village Vanguard