An estuary is a partially enclosed brackish water body with one or more streams or streams flowing into it, and with a free open sea connection.
Estuary forms a transition zone between the river environment and the maritime environment. They are subject to the influence of the sea - such as tides, waves, and the influx of salt water - and to the influence of rivers - such as freshwater flow and sediment. Mixing of seawater and fresh water provides high levels of nutrients both in the water column and in the sediments, making the estuary among the world's most productive natural habitats.
Most estuaries formed during the Holocene epoch with flooded valleys are covered by glacial river or valley when sea level began to rise about 10,000-12,000 years ago. Estuaries are usually classified according to their geomorphological features or water circulation patterns. They can have many different names, such as bay, harbor, lagoon, inlet, or sound, although some of these water bodies do not strictly meet the definition of the estuary above and may be completely copied.
The banks of many estuaries are among the most populous regions of the world, with about 60% of the world's population living along the estuary and coast. As a result, many estuaries suffer degradation from a variety of factors including: sedimentation from soil erosion from deforestation, overgrowing, and other poor farming practices; overfishing; drainage and filling of wetlands; eutrophication due to excessive nutrients from waste and animal waste; pollutants including heavy metals, polychlorinated biphenyls, radionuclides and hydrocarbons from waste inputs; and diking or dammed for flood control or water diversion.
Video Estuary
Definisi
The word "estuary" comes from the Latin aestuarium which means the inlet of the sea tide, which itself comes from the term aestus , which means pairs. There are many definitions proposed to describe an estuary. The most widely accepted definition is: "semi-enclosed seawater bodies, which have free open sea connections, and where measurable sea water is diluted with fresh water derived from soil drainage". However, this definition does not include a number of coastal water bodies such as coastal lagoons and brackish marine. A more comprehensive definition of the estuary is "a semi-closed water body connected to the sea as far as the boundary of the tide or limits of salt intrusion and receiving freshwater runoff, but freshwater flow may not last, recedes can be ignored ". This broad definition also includes fjords, lagoons, river estuaries, and tidal creeks. Estuary is a dynamic ecosystem that has connections to the open sea through which sea water passes by tidal rhythms. The sea water entering the estuary is dissolved by fresh water flowing from rivers and streams. The dilution pattern varies between different estuaries and depends on freshwater volume, tidal range, and water evaporation rate at the estuary.
Maps Estuary
Classification by geomorphology
sinking river valley
The drowning river valley is also known as the shores of the coastal plain. In places where the sea level rises relative to the land, sea water is increasingly penetrating into the river valley and the estuary topography remains similar to the river valley. This is the most common type of estuary in temperate climates. Well-studied estates include Muara Severn in the United Kingdom and Ems Dollard along the Dutch-German border.
This estuary width-to-depth ratios are usually large, appearing in a wedge shape (in cross section) on the inside and extending and deepening toward the sea. The depth of water rarely exceeds 30 m (100 ft). Examples of this type of estuary in the US are the Hudson River, Chesapeake Bay, and Delaware Bay along the Atlantic coast, and Galveston Bay and Tampa Bay along the Gulf Coast.
Type-Lagoon or bar-built
Estates built in bars are found in sedimentary sediments that keep pace with rising sea levels so that the estuaries are shallow and separated from the sea by the murmur of sand or barrier islands. They are relatively common in tropical and subtropical locations.
The estuary is semi-insulated from the waters of the sea by barrier beaches (barrier islands and spit barriers). The formation of a partial barrier beach encloses the estuary, with only a narrow opening that allows contact with sea water. Established estuaries are usually built on a gentle slope located along the tectonic continental edges and tense edges of the seaside. They are widespread along the Atlantic coast and the Gulf of America in areas with sedimentary sedimentation of sedimentary beaches and where tidal ranges are less than 4 m (13 ft). The barrier beach that includes the built estuary bar is built in several ways:
- builds offshore bars with wave action, where the sand from the seabed is deposited in longitudinal bars parallel to the shoreline,
- reworking sedimentary effluents from rivers with waves, currents, and winds to shore, overwash, and sand dunes,
- swallowed the coastal ridges (mountains evolved from the erosion of coastal sedimentary plains about 5000 years ago) due to rising sea levels and resulted in violations of mountains and coastal lowland floods, forming shallow lagoons, and li>
- elongation of salivary obstacles from tanjung erosion due to longshore action currents, with saliva growing toward coastal aberrations.
Barrier beaches are formed in shallow waters and generally align with coastlines, producing long and narrow estates. The average water depth is usually less than 5 m (16 ft), and rarely exceeds 10 m (33 ft). Examples of bar-built estates are Barnegat Bay, New Jersey; Laguna Madre, Texas; and Pamlico Sound, North Carolina.
Fjord-type
Fjords are formed where the pleistocene glacier deepens and extends the existing river basin so that they become U-shaped in the cross section. In their mouths there are usually stones, rods or glacial sediment sills, which have the effect of modifying estuarine circulation.
Estuary type fjord formed in a deeply eroded valley formed by glaciers. This U-shaped estuary usually has steep sides, stone base, and underwater sacs contoured by glacial motion. The estuary is the most shallow in its mouth, where the glacial morain or rock bar terminals form a frame that limits the flow of water. In the upper reaches of the estuary, the depth may exceed 300 m (1,000 ft). The width-to-depth ratio is generally small. At very shallow estuaries, tidal oscillation only affects water down to the depth of the window sill, and the deeper water from it can remain stagnant for a very long time, so only occasional water exchange occurs in the estuary. with the ocean. If the depth of the threshold is deep, the water circulation is less restricted, and there is a slow but steady exchange of water between the estuary and the ocean. Fjord-type estuaries can be found along the Alaska coast, Puget Sound region in western Washington state, British Columbia, eastern Canada, Greenland, Iceland, New Zealand and Norway.
produced tectonically
The estuary is formed by a sink or ground cut from the ocean by a movement of soil associated with a fault, a volcano, and a landslide. Flooding from rising sea levels eustatic during the Holocene Epoch has also contributed to the formation of this estuary. There are only a small number of estuaries produced tectonically; one example is the San Francisco Bay, formed by the crust movement of the San Andreas fault system that causes flooding downstream of the Sacramento and San Joaquin rivers.
Classification by water circulation
Salt wedge
In this type of estuary, river output greatly exceeds sea input and tidal effects have little importance. Freshwater floats above sea water in layers that gradually thin out as it moves toward the sea. The denser seawater moves to the mainland along the bottom of the estuary, forming a thinner wedge-shaped layer as it approaches the land. As the difference in velocity develops between the two layers, the shear forces produce internal waves at the interface, blending the seawater upward with fresh water. An example of a salt wedge estuary is the Mississippi River.
Partially mixed
As tidal eaters rise, the river output becomes less than the sea input. Here, the current induced turbulence causes the mixing of the entire water column so that the salinity varies more longitudinally than vertically, leading to moderately stratified conditions. Examples include Chesapeake Bay and Narragansett Bay.
Well-mixed
The tidal mixing forces exceed the river output, resulting in well-mixed water columns and loss of vertical salinity gradients. The freshwater-water barrier is removed due to the intense mixing and eddy turbulent effects. The lower parts of Delaware Bay and the Raritan River in New Jersey are examples of homogeneous vertical estuaries.
Inverse
The inverse estuary occurs in dry climates where evaporation greatly exceeds freshwater inflow. The maximum salinity zone is formed, and the flow of rivers and ocean waters closes to the surface towards this zone. This water is pushed down and spread along the bottom either toward the sea and the land direction. An example of an upside estuary is Spencer Gulf, South Australia.
Intermittent
This type of estuary varies dramatically depending on freshwater input, and is able to change from fully embayment of the sea to one of the other estuary types.
Physiochemical variations
The most important variable characteristics of estuary water are the concentration of dissolved oxygen, salinity and sediment load. There is extreme spatial diversity in salinity, with a range close to zero at the tidal boundary of tributary rivers up to 3.4% at the mouth of the estuary. At each point the salinity will vary over time and season, making it a harsh environment for the organism. Sediments often settle in the intertidal mud that is very difficult to colonize. There is no point of attachment to algae, so vegetation-based habitats are not formed. Sediments can also clog feeding and species respiratory structures, and special adaptations exist within mudflate species to address this problem. Finally, the variation of dissolved oxygen can cause problems for life forms. Nutrient-rich sediments from manmade sources can increase the life cycle of primary production, which may cause decay to eventually dissolve dissolved oxygen from water; thus hypoxic or anoxic zones may develop.
Implications for marine life
Estuaries provide habitat for a large number of organisms and support very high productivity. Estuary provides habitat for many breeding fish, depending on their location in the world, such as salmon and sea fish. Also, migratory bird populations, such as the black tailed goddess, make important use of the estuary.
The two main challenges of estuary life are salinity and sedimentation variability. Many species of fish and invertebrates have various methods to control or adjust to shifting salt concentrations and are called osmoconformers and osmoregulators. Many animals also dig to avoid predation and live in a more stable sedimentary environment. However, large numbers of bacteria are found in sediments that have very high oxygen demand. This reduces oxygen levels in sediments that often result in partial anoxic conditions, which can be further aggravated by limited water flux.
Phytoplankton is a major prime producer in the estuary. They move with bodies of water and can be pounded in and out with ups and downs. Their productivity is largely dependent on the turbidity of the water. The main phytoplankton presentation is the diatoms and dinoflagellates that are abundant in the sediments.
It is important to remember that the main source of food for many estuarine organisms, including bacteria, is the detritus of the sedimentation settlement.
Human impact
Of the thirty-two largest cities in the world in the early 1990s, twenty-two were in the estuary.
As an ecosystem, estuaria is threatened by human activities such as pollution and overfishing. They are also threatened by waste, coastal settlements, land clearing and more. Estuary is influenced by events far upstream, and concentrates materials such as pollutants and sediments. Industrial and agricultural, agricultural and domestic runoff and waste enter the river and discharge to the estuary. Contaminants can be introduced that are not destroyed 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 mud of the bay: the geological record of human activity in the last century. The composition of the biofilm element reflects the estuary area affected by human activity, and over time can shift the basic composition of the ecosystem, and changes that can be changed or can not be altered in the abiotic and biotic parts of the system from the ground up.
For example, Chinese and Russian industrial pollution, such as phenols and heavy metals, has destroyed fish stocks in the Amur River and damaged estuarine soils.
Estates tend to be natural eutrophic because water runoff discharges nutrients to the estuary. With human activities, soil runoff also now includes many of the chemicals used as fertilizers in agriculture as well as waste from livestock and humans. Excess oxygen that drains oxygen in the water can cause hypoxia and the formation of dead zones. This can result in degradation of water quality, fish, and other animal populations. Overfishing also occurs. Chesapeake Bay once had a population of oysters that had almost disappeared due to overfishing. Oysters filter out these pollutants, and eat them or form them into small packets stored at the bottom where they are harmless. Historically, oysters filtered the entire volume of excess water from the estuary every three or four days. Today the process takes almost a year, and sediment, nutrients, and algae can cause problems in the local waters.
Example
See also
References
External links
- An animated documentary about NOAA's Chesapeake Bay.
- "Habitat: Estuary - Characteristics". www.onr.navy.mil. Archived from the original on 2009-05-17 . Retrieved 2009-11-17 .
- The Estuary Guide (Based on experience and R & D in the UK)
Source of the article : Wikipedia
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