B. KARTHIK CLASS “C” E. V. S PROJECT Problems nutrients, such as nitrogen in the form of nitrates and ammonia can intensify this fertilizing effect, especially in nutrient poor rivers in remote areas as well as estuaries or coastal areas. * runoff from land cleared for agriculture, especially where fertilizers and manure have been applied in quantities that exceed nutritional requirements of crops * runoff from forestry and urban expansion * industrial emissions to soils and water (e. g. ulp and paper and mining) municipal and household wastewater discharge, including septic systems lown dust from bare soils. Excess phosphorus can result in abundant growth of aquatic plants. This can lead to a shift in the assemblages of fish and invertebrates toward less desirable species, including pollution tolerant ones which may include invasive species. blue green algae can form blooms under certain conditions, such as high nutrient loadings and warm temperatures, and cause unpleasant taste and odour problems in drinking water.
Some of these bacteria can release toxins in the water which can pose health risks to humans and animals Decaying and unsightly algal and aquatic plant growths an also clog intake pipes and impair navigation reducing the aesthetic and recreational value of aquatic ecosystems. Additionally, fish kills can occur as a result of concurrent declines in dissolved oxygen. THE END Wetlands, rivers, lakes, and coastal estuaries are all aquatic ecosystems”critical elements of Earth’s dynamic processes and essential to human economies and health.
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Wetlands connect land and water, serving as natural filters, reducing pollution, controlling floods, and acting as nurseries for many aquatic species. Rivers, lakes, and estuaries serve as important transportation, recreation, and wildlife hubs. Coral reefs deliver ecosystem services to tourism, fisheries and shoreline protection. The annual global economic value of coral reefs was estimated at IJS$ 375 billion in 2002. However, coral reefs are fragile ecosystems, partly because they are very sensitive to water temperature.
They are under threat from climate change, oceanic acidification, blast fishing, cyanide fishing for aquarium fish, overuse of reef resources, and harmful land-use practices, including urban and agricultural runoff and water pollution, which can harm reefs by encouraging excess algal growth. [5 7] The banks of many estuaries are amongst the most heavily populated areas of the world, with about 60% of the world’s population living along estuaries and the coast.
As a result, many 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, polychlorinated biphenyls, radionuclides and hydrocarbons from sewage inputs; and diking or damming for flood control or water diversion. ] Wetlands are among the most productive ecosystems in the world, comparable to rain forests and coral reefs. An immense variety of species of microbes, plants, insects, amphibians, reptiles, birds, fish, and mammals can be part of a wetland ecosystem. Physical and chemical features such as climate, landscape shape (topology), geology, and the movement and abundance of water help to determine the plants and animals that inhabit each wetland. The complex, dynamic relationships among the organisms inhabiting the wetland environment are referred to as food webs.
Wetlands play an ntegral role in the ecology of the watershed. The combination of shallow water, high levels of nutrients, and primary productivity is ideal for the development of organisms that form the base of the food web and feed many species of fish, amphibians, shellfish, and insects. Many species of birds and mammals rely on wetlands tor t , water, and shelter, especially during migration and breeding. Wetlands’ microbes, plants, and wildlife are part of global cycles for water, nitrogen, and sulfur.
Furthermore, scientists are beginning to realize that atmospheric maintenance may be an additional wetlands function. Wetlands store carbon within their plant communities and soil instead of releasing it to the atmosphere as carbon dioxide. Thus wetlands help to moderate global climate conditions. Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny animals found in marine waters that contain few nutrients.
Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps belong to a group of animals known as Cnidaria, which also includes sea anemones and Jellyfish. Unlike sea anemones, coral polyps secrete hard arbonate exoskeletons which support and protect their bodies. Reefs grow best in warm, shallow, clear, sunny and agitated waters. often called “rainforests of the sea”, coral reefs form some of the most diverse ecosystems on Earth.
They occupy less than 0. 1% of the world’s ocean surface, about half the area of France, yet they provide a home for 25% of all marine including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates and other cnidarians.  Paradoxically, coral reefs flourish even though they are surrounded by ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, ut deep water and cold water corals also exist on smaller scales in other areas.
An estuary is a partly 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. [l] Estuaries form a transition zone between river environments and maritime 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 inflows of both sea water and fresh water provide high levels of nutrients in both the water olumn and sediment, making estuaries among the most productive natural habitats in the world. 2] Most existing estuaries were formed during the Holocene epoch by the flooding of river-eroded or glacially scoured valleys when the sea level began to rise about 10,000-12,000 years ago.  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 some of these water bodies do not strictly meet the above definition of an estuary and may be fully saline.
The ecosystem of a river is the river viewed as a system operating in its natural environment, and includes biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions.  River ecosystems are prime examples of lotic ecosystems. Lotic refers to flowing water, from the Latin lotus, washed. Lotic waters range from springs only a few centimeters wide to major rivers kilometers in width.  Much of this article applies to lotic ecosystems in general, including related lotic systems such as streams and springs.
Lotic ecosystems can be contrasted with lentic ecosystems, which involve relatively still terrestrial waters such as lakes and ponds. Together, these two fields form the more general study area of freshwater or aquatic ecology. The following unifying characteristics make the ecology of running waters unique from that of other aquatic habitats.  * Flow is unidirectional. * There is a state ot continuous physical change. * There is a high degree of spatial and temporal heterogeneity at all scales (microhabitats). * Variability between lotic systems is quite high. * The biota is specialized to live with flow conditions.