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River Basin Ecosystems
River basin ecosystems consist of rivers, floodplains, lakes, coastal mangroves, mangrove swamps, saltmarshes, freshwater marshes, ponds, coastal lagoons, coastal waters, deltas, estuaries, mudflats, reservoirs and dams. And according to the Ramsar Convention, all these ecosystems are also known as wetlands. Ramsar defines wetlands as: "areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water, the depth of which at low tide does not exceed six metres".
News Articles Floodplain Reforestation Efforts Lack Diversity Books Discover European Wetlands by N. LeRoy Poff (Colorado State University ), Mark M. Brinson (East Carolina University) & John W. Day, Jr. (Louisiana State University)
.bmp) Coastal Lagoons
Coastal Lagoons is shallow sounds, ponds, or lakes generally near but separated from or communicating with the open sea, with a brackishwater environment. One of the coastal lagoons in India is Chilika Lagoon. It is the largest brackish water lagoon with estuarine character that sprawls along the east coast. It is the largest wintering ground for migratory waterfowl found anywhere on the Indian sub-continent. It is one of the hotspot of biodiversity in the country, and some rare, vulnerable and endangered species listed in the IUCN Red List of threatened Animals inhabit the Lake area for at least a part of their life cycle. The total number of fish species are reported to be 225 (Dean and Saaltink, 1991). Along with a variety of phytoplankton, algae and aquatic plants, the Lake region also supports over 350 species of non-aquatic plants (Panda and Pattnaik, 1988). A survey of the fauna of Chilika Lake carried out by the Zoological Survey of India in 1985-87 recorded over 800 species in and around the lagoon. This list includes a number of rare, threatened and endangered species, including the Barakudia limbless skink.
The Lagoon is a highly productive ecosystem, with rich fishery resources. The rich fishing ground sustain the livelihood of more than 1,00,000 fisher folk who live in and around the Lake. Based on its rich biodiversity and socio-economic importance, Chilika Lake was designated by the government of India as a Ramsar Site in 1981, under the Ramsar Convention on Wetlands. It is also included in the list of wetlands selected for intensive conservation and management by the Ministry of Environment and Forests, Government of India.
The Nalaban Island within the Lake is notified as a Bird Sanctuary under Wildlife (Protection) Act, the lagoon is also identified as a priority site for conservation and management by the National Wetland coral reefs Committee of Ministry ofEnvironment & Forests, Government of India.
The waterspread area of the Lake varies between 1165 to 906 sq km during the monsoon and summer respectively. A 32 km long, narrow, outer channel connects the main lagoon to the Bay of Bengal, near the village Arakhakuda. The mouth connecting the channel to the sea is close to the north eastern end of the Lake. High tides near this inlet mouth drive in salt water through the channel during the dry months, from December to June. With the onset of the rains, the rivers falling into the northern zone are in spate, causing fresh water currents which gradually push the sea water out. As a result of these dynamics the inlet mouth constantly changes position.
Chilika supports the largest congregation of aquaticbirds in the country, particularly during the winter. Flocks of migratory water-fowl arrive from as far as the Caspian Sea, Lake Baikal, Aral Sea, remote parts of Russia, Kirghiz steppes of Mongolia, Central and South East Asia, Ladakh and the Himalayas,tofeed and breed in its fertile waters. In 1989-90 an estimated two million birds visited the lake.
Deltas and estuaries
Estuary
An estuary is a semi-enclosed coastal body of water which has a free connection with the open sea and within which sea water mixes with fresh water. Estuaries are protected from the full force of the ocean by mudflats, sandspits and barrier islands. The key feature of an estuary is that it is a mixing place for sea water and a significantly-sized river to supply fresh water. A tide is a necessary component to maintain a dynamic relationship between the two waters. Though something in the nature of an estuary can exist in a non-tidal sea, such areas go by names such as lagoon, étang or laguna. In non-tidal seas, the rivers naturally form deltas rather than estuaries.
Every estuary is unique; each individual ecosystem has different components that complete the estuarine habitat. One estuary may be enclosed by marshes and barrier islands, while another estuary's borders are the coastline and reefs. Bodies of water that may be estuaries are: sloughs, bays, harbors, sounds, inlets and bayous.
A plethora of organisms can be found in estuaries, organisms specially adapted to the "brackish" estuarine waters. Estuaries are homes to all kind of terrestrial or land-based plants and animals, such as wood storks, pelicans, coniferous and deciduous trees and butterflies. Estuaries are also homes to unique aquatic plants and animals, such as sea grass, sea turtles and sea lions.
Estuaries are among the most biologically productive ecosystems on the planet. More than two thirds of the fish and shellfish we eat spend some part of their lives in estuaries. These ecosystems also provide many other important ecological functions; they act as filters for terrestrial pollutants and provide protection from flooding. Estuaries also have economic importance. These dynamic bodies of water provide us with an important source of food, but are also a popular tourist destination. Millions of people visit the nation's estuaries each year to boat, swim, bird watch and fish.
The fragile balance of these productive estuarine environments may be easily destroyed by human activities. Changes in water quality or alterations, by dredging and construction, to the multiple components of estuaries can result in harmful changes in the ecosystem. The purpose of National Estuaries Day is to promote the need to protect these important areas and to learn how we can safeguard these irreplaceable resources.
Delta
A delta is the mouth of a river where it flows into an ocean, sea, or lake, building outwards (as a deltaic deposit) from sediment carried by the river and deposited as the water current is dissipated. Deltaic deposits of larger, heavily-laden rivers are characterised by the river channel dividing into multiple streams (distributaries), these divide and come together again to form a maze of active and inactive channels.
Delta formation
At the final course of a river, when it enters the sea, it mixes with the surrounding water, and its velocity of flow is checked, causing it to deposit its load of gravel, sand, silt and clay. The first materials deposited are the gravel and sand, as they are by far the heaviest and coarsest. Next to be dropped is the silt. Because it is fine, the clay is transported in suspension quite far out in the sea. When salt water causes the clay to flocculate, it becomes heavier and sinks. As layers upon layers of alluvial materials are deposited, a platform of alluvium is built up and it eventually rises above the water, which can now be called the delta. The water then overflows the banks into different channels called distributaries, which build up their own levees. The vegetation that later grows on the alluvium stabilizes the delta.
The most famous delta is that of the Nile River, and it is this delta from which the term is derived, because the Nile delta has a very characteristic triangular shape, like the (upper-case) Greek letter delta (Δ). Other rivers with notable deltas include the Ganges/Brahmaputra combination (this delta spans most of Bangladesh and West Bengal), the Niger, the Amazon, the Mississippi, the Sacramento-San Joaquin, the Rhine, the Rhône, the Danube, the Ebro, the Volga, the Lena, the Tigris-Euphrates, the Indus, the Krishna-Godavari, the Kaveri, the Irrawaddy, and the Mekong.
In rare cases the river delta is located inside of a large valley and is called an inverted river delta. Sometimes a river will divide into multiple branches in an inland area, only to rejoin and continue to the sea; such an area is known as an inland delta, and often occur on former lake beds. The Niger Inland Delta is the most famous example; another is the Danube Inland Delta on the Little Alföld.
Coastal Waters
Coastal water is same meaning as marine coastal waters.
Lakes and Ponds
Lakes and ponds are permanently wet year round. The main difference between a lake and a pond is the size. A lake is usually defined as a body of water large enough to have at least one wind-swept beach; ponds usually are not large enough for winds to blow across the water and create waves to wash away the plants that may be trying to take root. A lake is too deep for rooted plants to grow except near the shore.
Ponds are inland bodies of fresh water that are usually less than six or seven feet deep. Ponds have plants growing on the bottom of them from one side to the other.There are two types of ponds, permanent and temporary. Permanent ponds exist year-round. Temporary or vernal ponds usually develop in the spring, when rain and melting snow fill in depressions in the ground, and dry up in the summer. Vernal ponds are often breeding grounds for frogs and other amphibians. Some organisms in vernal ponds are adapted to survive through the dry season. Some algae and protozoa dig into the mud and make a cyst or hard cover out of slime! This protects the organisms until water fills the pond in the spring.
Ponds form when water begins to fill in a depression in the ground. Early plants or pioneers start growing on the bottom of the pond. Eventually plants called emergents start to grow on the edge of the pond. Over time the plants in and around a pond grow and die and decompose. As the plants decompose, layers of soil build up and the pond becomes shallower and shallower. As the pond becomes more shallow, the plants on the edge of the pond may begin to grow in the pond. When this happens, the pond becomes a marsh. As the marsh plants grow and die and decompose, trees may begin to grow in the marsh. Now the marsh is a swamp. Over time, if the swamp dries up, the land may become a forest or grassland! All of this happens over hundreds of years!
Lakes and ponds are sometimes classified by the amounts and kinds of organic materials produced and decayed from the processes of photosynthesis and decomposition. Lakes and ponds, where there is a good balance between photosynthesis and decomposition, are said to be oligotrophic. The middle of Lake Michigan can be classified as oligotrophic. When the balance is upset between these two processes, either too much organic material accumulates without getting decomposed adequately or too many bacteria are present and an overabundance of decomposition occurs. Eutrophic lakes and ponds have an abundance of nutrients, and an abundance of decay-causing organisms to break down all the organic material being produced. Their bottoms fill up with rich sediment. Sometimes there are so many bacteria, that oxygen is depleted and the waters become stagnant. Most inland lakes are eutrophic. In dystrophic lakes and ponds there is a lack of decomposition from bacteria and the nutrients build up.
Lakes By the Numbers
There are about 30,000 cubic miles (48,270 cubic kilometers) of lake water in the world. Lake water makes up about 0.4 percent of all the world's fresh water! About 80 percent of all the lake water in the world can be found in 40 large lakes and 70 percent of all the lake water in the world is found in North America, Africa, and Asia. Close to half of all the world's lakes are in Canada! The deepest freshwater lake in the world is Lake Baikal in Siberia. It is 5371 feet (1637 meters) deep! Lake Superior is the largest freshwater lake in the world. It has a surface area of 31,700 square miles (51,005 square kilometers) and is over 380 miles (611 kilometers) long and at its widest part, 160 miles across (257 kilometers)! Parts of Lake Superior are in Michigan, Minnesota, Wisconsin and Ontario, Canada.
Mangroves & Marshes
Predominantly tropical or subtropical brackish/marine swamps. Saltmarshes have an excess of sodium chloride as their main environmental feature.
Peatlands
Peatlands represent over half of the world’s wetland area and a significant proportion of the global peatland area occurs in the tropical and sub-tropical region. Andriesse (1988) gave the total are of tropical and sub-tropical peatland of 35.8 Million ha of which 57% of it is located in the region of Southeast Asia.
Peat are partially decomposed organic matters accumulated over a period of time under saturated condition. They show a wide range in degree of decomposition. Peat has high field moisture content (>200%), low bulk density of <1.0 Mg/m3 and generally low pH of 3-5. Another intrinsic characteristic of peat is irreversible drying. Intensive drying of peat soil would leads to irreversible drying. After exposure to sun, the materials become very difficult to re-wet, hence losing its water holding capability. Peatlands are classified as marginal land for agriculture development due to its low fertility and its acidic nature. Amount of nutrients isextremely little. Cultivation of peatland for crop would require high input of fertilizer and liming.
The functions of Peatlands such as Peat Swamp include regulation and controlling of the hydrology of entire catchment; acting as natural filters by removing toxic compounds from the environment and also as a buffer zone between the salt and fresh water systems. Besides the regulating functions, peatswamp produces valuable timber trees such as Ramin and Merbau. It is a unique ecosystem harbouring many indigenous and endemic species of flora and fauna.
Read more on peatlands here.
Ponds
Pond is a small natural body of standing fresh water filling a surface depression, usually smaller than a lake .
Reservoirs and dams
A pond or lake built for the storage of freshwater, usually by the construction of a dam across a river.
Rivers and floodplains
Rivers comprise large, natural freshwater surface streams having a permanent or seasonal flow and moving toward a sea, lake, or another river in a definite channel, and flood plains are the relatively smooth valley floors adjacent to and formed by alluvia.
To read more issues about river basin ecosystems go to: Wetlands Help-line
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