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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. Soil Nitrogen Testing N-Testing is a technique that helps farmers optimize the amount of fertilizer applied to crops. 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. Please use one of the following formats to cite this article in your essay, paper or report: See Vitamin , Mineral nutrient , Protein nutrient. If a plant, with its root system intact, is provided with a known amount of radioactive ions like 35 SO4 or 32 P for about 30 minutes, it is possible to determine the total amount of ions taken up by the root system by measuring the amount of radioactivity left in the exogenously provided solution.
Phosphate adheres tightly to soil, so it is mainly transported by erosion. Once translocated to lakes, the extraction of phosphate into water is slow, hence the difficulty of reversing the effects of eutrophication. Cultural eutrophication is the process that speeds up natural eutrophication because of human activity. Extra nutrients are also supplied by treatment plants, golf courses, fertilizers, farms including fish farms , as well as untreated sewage in many countries.
When algae die, they decompose and the nutrients contained in that organic matter are converted into inorganic form by microorganisms. This decomposition process consumes oxygen, which reduces the concentration of dissolved oxygen.
The depleted oxygen levels in turn may lead to fish kills and a range of other effects reducing biodiversity. Nutrients may become concentrated in an anoxic zone and may only be made available again during autumn turn-over or in conditions of turbulent flow. Enhanced growth of aquatic vegetation or phytoplankton and algal blooms disrupts normal functioning of the ecosystem, causing a variety of problems such as a lack of oxygen needed for fish and shellfish to survive. The water becomes cloudy, typically coloured a shade of green, yellow, brown, or red.
Eutrophication also decreases the value of rivers, lakes and aesthetic enjoyment. Health problems can occur where eutrophic conditions interfere with drinking water treatment. Human activities can accelerate the rate at which nutrients enter ecosystems. Runoff from agriculture and development, pollution from septic systems and sewers , sewage sludge spreading, and other human-related activities increase the flow of both inorganic nutrients and organic substances into ecosystems.
Elevated levels of atmospheric compounds of nitrogen can increase nitrogen availability. Phosphorus is often regarded as the main culprit in cases of eutrophication in lakes subjected to "point source" pollution from sewage pipes. The concentration of algae and the trophic state of lakes correspond well to phosphorus levels in water.
Studies conducted in the Experimental Lakes Area in Ontario have shown a relationship between the addition of phosphorus and the rate of eutrophication. Humankind has increased the rate of phosphorus cycling on Earth by four times, mainly due to agricultural fertilizer production and application. Between and , an estimated ,, tonnes of phosphorus was applied to Earth's surface, primarily on croplands.
Although eutrophication is commonly caused by human activities, it can also be a natural process, particularly in lakes. Eutrophy occurs in many lakes in temperate grasslands, for instance. Paleolimnologists now recognise that climate change, geology, and other external influences are critical in regulating the natural productivity of lakes.
Some lakes also demonstrate the reverse process meiotrophication , becoming less nutrient rich with time. Eutrophication is a common phenomenon in coastal waters. In contrast to freshwater systems, nitrogen is more commonly the key limiting nutrient of marine waters; thus, nitrogen levels have greater importance to understanding eutrophication problems in salt water. Estuaries tend to be naturally eutrophic because land-derived nutrients are concentrated where run-off enters a confined channel.
Upwelling in coastal systems also promotes increased productivity by conveying deep, nutrient-rich waters to the surface, where the nutrients can be assimilated by algae. Examples of anthropogenic sources of nitrogen-rich pollution include seacage fish farming and discharges of ammonia from the production of coke from coal. In addition to runoff from land, fish farming wastes and industrial ammonia discharges, atmospheric fixed nitrogen can enter the open ocean. Terrestrial ecosystems are subject to similarly adverse impacts from eutrophication.
Many terrestrial plant species are endangered as a result of soil eutrophication, such as the majority of orchid species in Europe. In meadows, tall grasses that can take advantage of higher nitrogen levels may change the area so that natural species may be lost. Species-rich fens can be overtaken by reed or reedgrass species.
Forest undergrowth affected by run-off from a nearby fertilized field can be turned into a nettle and bramble thicket. Chemical forms of nitrogen are most often of concern with regard to eutrophication, because plants have high nitrogen requirements so that additions of nitrogen compounds will stimulate plant growth. Nitrogen is not readily available in soil because N 2 , a gaseous form of nitrogen, is very stable and unavailable directly to higher plants.
Terrestrial ecosystems rely on microbial nitrogen fixation to convert N 2 into other forms such as nitrates. However, there is a limit to how much nitrogen can be utilized. Ecosystems receiving more nitrogen than the plants require are called nitrogen-saturated. Saturated terrestrial ecosystems then can contribute both inorganic and organic nitrogen to freshwater, coastal, and marine eutrophication, where nitrogen is also typically a limiting nutrient.
However, because phosphorus is generally much less soluble than nitrogen, it is leached from the soil at a much slower rate than nitrogen. Consequently, phosphorus is much more important as a limiting nutrient in aquatic systems. Eutrophication was recognized as a water pollution problem in European and North American lakes and reservoirs in the midth century. Many ecological effects can arise from stimulating primary production , but there are three particularly troubling ecological impacts: When an ecosystem experiences an increase in nutrients, primary producers reap the benefits first.
In aquatic ecosystems, species such as algae experience a population increase called an algal bloom. 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. 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 , otherwise called "nuisance algae" or "harmful algal blooms", are toxic to plants and animals. Toxic compounds they produce 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. 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 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.
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.
Iron mg Calories Clams, canned, drained, 3 oz Non-Dairy Food Sources of Calcium ranked by milligrams of calcium per standard amount; also calories in the standard amount.
The bioavailability may vary. Some plant foods have calcium that is well absorbed, but the large quantity of plant foods that would be needed to provide as much calcium as in a glass of milk may be unachievable for many.
Many other calcium-fortified foods are available, but the percentage of calcium that can be absorbed is unavailable for many of them. Food Sources of Calcium ranked by milligrams of calcium per standard amount; also calories in the standard amount.
Food Sources of Magnesium ranked by milligrams of magnesium per standard amount; also calories in the standard amount. Food Sources of Dietary Fiber ranked by grams of dietary fiber per standard amount; also calories in the standard amount. Foods are from single nutrient reports, which are sorted either by food description or in descending order by nutrient content in terms of common household measures. Mixed dishes and multiple preparations of the same food item have been omitted.
Food Sources of Vitamin C ranked by milligrams of vitamin C per standard amount; also calories in the standard amount.