Chislock, Today, the main control mechanism of the eutrophic process is based on prevention techniques, namely removal of the nutrients that are introduced into water bodies from the water. It would be sufficient to reduce the concentrations of one of the two main nutrients nitrogen and phosphorus , in particular phosphorus which is considered to be the limiting factor for the growth of algae, acting on localised loads loads associated with waste water and widespread loads phosphorus loads determined by diffuse sources such as land and rain.
The load is the quantity milligrams, kilograms, tons, etc. The possible activities to be undertaken to prevent the introduction of nutrients and to limit phosphorus loads can be summarised as follows www3. Conclusions Water is not a commercial product like any other but rather a heritage which must be defended and protected, especially in the presence of a global decline in the availability of drinking water and increase in its demand.
Despite the considerable efforts made to improve the water quality by limiting nutrient enrichment, cultural eutrophication and the resulting algal blooms continue to be the main cause of water pollution. The prevention and protection action that countries must adopt to safeguard the quality of surface water as requested not only by the scientific community and other experts, but to an increasing extent also by citizens and environmental organisations, is therefore increasingly important ec. Management of the eutrophic process is a complex issue that will require the collective efforts of scientists, policy makers and citizens.
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Home page News What is eutrophication? Causes, effects and control. All the topics All the topics facts News and events reports. This is particularly true of stratified systems such as, for instance, lakes during summer when concentrations of molecular oxygen may reach levels of less than about one milligram per litre—a threshold for various biological and chemical processes. Low oxygen levels can be further exacerbated by water blooms that often accompany nutrient loading of waters and may poison wildlife. In the Black Sea and elsewhere, hypoxic waters from cultural eutrophication have resulted in massive fish kills, with rippling effects throughout the food chain and local economies.
Coastal marine systems also may be affected by this process. On a global scale, the input of organic matter by rivers into the oceans today is twice the input in prehuman times, and the flux of nitrogen, together with that of phosphorus, has more than doubled. This excess loading of carbon, nitrogen, and phosphorus has led to cultural eutrophication of numerous marine systems, including several polluted eastern U. Much of the phosphorus in streams and lakes is delivered from agriculture, both through soil erosion and fertilizer runoff.
Nitrogen from municipal sewage treatment plants and the direct runoff from animal feedlots are serious problems in many places. Pollution control and improved municipal, industrial, and agricultural practices could do much to curb the cultural eutrophication of inland and coastal waters.
You are using an outdated browser. Please upgrade your browser to improve your experience and security. Article Media. Info Print Cite. Algal blooms limit the sunlight available to bottom-dwelling organisms and cause wide swings in the amount of dissolved oxygen in the water. Oxygen is required by all aerobically respiring plants and animals and it is replenished in daylight by photosynthesizing plants and algae. Under eutrophic conditions, dissolved oxygen greatly increases during the day, but is greatly reduced after dark by the respiring algae and by microorganisms that feed on the increasing mass of dead algae.
When dissolved oxygen levels decline to hypoxic levels, fish and other marine animals suffocate. As a result, creatures such as fish, shrimp, and especially immobile bottom dwellers die off.
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Zones where this occurs are known as dead zones. Eutrophication may cause competitive release by making abundant a normally limiting nutrient. This process causes shifts in the species composition of ecosystems. For instance, an increase in nitrogen might allow new, competitive species to invade and out-compete original inhabitant species. This has been shown to occur  in New England salt marshes. In Europe and Asia, the common carp frequently lives in naturally Eutrophic or Hypereutrophic areas, and is adapted to living in such conditions.
The eutrophication of areas outside its natural range partially explain the fish's success in colonising these areas after being introduced.
Some algal blooms resulting from eutrophication, otherwise called "harmful algal blooms", are toxic to plants and animals. Toxic compounds can make their way up the food chain , resulting in animal mortality. When the algae die or are eaten, neuro - and hepatotoxins are released which can kill animals and may pose a threat to humans. Examples include paralytic , neurotoxic, and diarrhoetic shellfish poisoning.
Learn more about Eutrophication
Other marine animals can be vectors for such toxins, as in the case of ciguatera , where it is typically a predator fish that accumulates the toxin and then poisons humans. In order to gauge how to best prevent eutrophication from occurring, specific sources that contribute to nutrient loading must be identified. There are two common sources of nutrients and organic matter: point and nonpoint sources.
Point sources are directly attributable to one influence.
In point sources the nutrient waste travels directly from source to water. Point sources are relatively easy to regulate. Nonpoint source pollution also known as 'diffuse' or 'runoff' pollution is that which comes from ill-defined and diffuse sources. Nonpoint sources are difficult to regulate and usually vary spatially and temporally with season , precipitation , and other irregular events. It has been shown that nitrogen transport is correlated with various indices of human activity in watersheds,   including the amount of development.
There are three reasons that nonpoint sources are especially troublesome: . Nutrients from human activities tend to accumulate in soils and remain there for years. It has been shown  that the amount of phosphorus lost to surface waters increases linearly with the amount of phosphorus in the soil.
Thus much of the nutrient loading in soil eventually makes its way to water. Nitrogen, similarly, has a turnover time of decades. Nutrients from human activities tend to travel from land to either surface or ground water. Nitrogen in particular is removed through storm drains , sewage pipes, and other forms of surface runoff. Nutrient losses in runoff and leachate are often associated with agriculture. Modern agriculture often involves the application of nutrients onto fields in order to maximise production.
However, farmers frequently apply more nutrients than are taken up by crops  or pastures. Regulations aimed at minimising nutrient exports from agriculture are typically far less stringent than those placed on sewage treatment plants  and other point source polluters. It should be also noted that lakes within forested land are also under surface runoff influences. Runoff can wash out the mineral nitrogen and phosphorus from detritus and in consequence supply the water bodies leading to slow, natural eutrophication. Nitrogen is released into the air because of ammonia volatilization and nitrous oxide production.
The combustion of fossil fuels is a large human-initiated contributor to atmospheric nitrogen pollution.
Atmospheric nitrogen reaches the ground by two different processes, the first being wet deposition such as rain or snow, and the second being dry deposition which is particles and gases found in the air. Any factor that causes increased nutrient concentrations can potentially lead to eutrophication. In modeling eutrophication, the rate of water renewal plays a critical role; stagnant water is allowed to collect more nutrients than bodies with replenished water supplies.
It has also been shown that the drying of wetlands causes an increase in nutrient concentration and subsequent eutrophication blooms. Eutrophication poses a problem not only to ecosystems , but to humans as well. Reducing eutrophication should be a key concern when considering future policy, and a sustainable solution for everyone, including farmers and ranchers, seems feasible.
What is eutrophication?
While eutrophication does pose problems, humans should be aware that natural runoff which causes algal blooms in the wild is common in ecosystems and should thus not reverse nutrient concentrations beyond normal levels. Cleanup measures have been mostly, but not completely, successful. Finnish phosphorus removal measures started in the mids and have targeted rivers and lakes polluted by industrial and municipal discharges.
One proposed solution to eutrophication in estuaries is to restore shellfish populations, such as oysters and mussels. Oyster reefs remove nitrogen from the water column and filter out suspended solids, subsequently reducing the likelihood or extent of harmful algal blooms or anoxic conditions. Seaweed kelp, Nonpoint pollution is the most difficult source of nutrients to manage. The literature suggests, though, that when these sources are controlled, eutrophication decreases. The following steps are recommended to minimize the amount of pollution that can enter aquatic ecosystems from ambiguous sources.
Studies show that intercepting non-point pollution between the source and the water is a successful means of prevention. Creating buffer zones near farms and roads is another possible way to prevent nutrients from traveling too far. Still, studies have shown  that the effects of atmospheric nitrogen pollution can reach far past the buffer zone. This suggests that the most effective means of prevention is from the primary source.
Laws regulating the discharge and treatment of sewage have led to dramatic nutrient reductions to surrounding ecosystems,  but it is generally agreed that a policy regulating agricultural use of fertilizer and animal waste must be imposed. In Japan the amount of nitrogen produced by livestock is adequate to serve the fertilizer needs for the agriculture industry.
Policy concerning the prevention and reduction of eutrophication can be broken down into four sectors: Technologies, public participation, economic instruments, and cooperation. As mentioned before, nonpoint sources of pollution are the primary contributors to eutrophication, and their effects can be easily minimized through common agricultural practices. Reducing the amount of pollutants that reach a watershed can be achieved through the protection of its forest cover, reducing the amount of erosion leeching into a watershed.
Also, through the efficient, controlled use of land using sustainable agricultural practices to minimize land degradation, the amount of soil runoff and nitrogen-based fertilizers reaching a watershed can be reduced. Because a major contributor to the nonpoint source nutrient loading of water bodies is untreated domestic sewage, it is necessary to provide treatment facilities to highly urbanized areas, particularly those in underdeveloped nations, in which treatment of domestic waste water is a scarcity.