Eutrophication

Eutrophication (from Greek eutrophos, "well-nourished"),[1] or hypertrophication, is when a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of algae.[2] This process may result in oxygen depletion of the water body.[3] One example is an "algal bloom" or great increase of phytoplankton in a water body as a response to increased levels of nutrients. Eutrophication is often induced by the discharge of nitrate or phosphate-containing detergents, fertilizers, or sewage into an aquatic system.

Potomac green water
The eutrophication of the Potomac River is evident from the bright green water, caused by a dense bloom of cyanobacteria.
Orange like Autumn
Eutrophication in a canal

Mechanism of eutrophication

Eutrophication most commonly arises from the oversupply of nutrients, most commonly as nitrogen or phosphorus, which leads to overgrowth of plants and algae in aquatic ecosystems. After such organisms die, bacterial degradation of their biomass results in oxygen consumption, thereby creating the state of hypoxia.

According to Ullmann's Encyclopedia, "the primary limiting factor for eutrophication is phosphate." The availability of phosphorus generally promotes excessive plant growth and decay, favouring simple algae and plankton over other more complicated plants, and causes a severe reduction in water quality. Phosphorus is a necessary nutrient for plants to live, and is the limiting factor for plant growth in many freshwater ecosystems. 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.[4] However, numerous literature report that nitrogen is the primary limiting nutrient for the accumulation of algal biomass.[5]

The sources of these excess phosphates are phosphates in detergent, industrial/domestic run-offs, and fertilizers. With the phasing out of phosphate-containing detergents in the 1970s, industrial/domestic run-off and agriculture have emerged as the dominant contributors to eutrophication.[6]

Sodium tripolyphosphate
Sodium triphosphate, once a component of many detergents, was a major contributor to eutrophication.
Eutrophicationmodel
1. Excess nutrients are applied to the soil. 2. Some nutrients leach into the soil where they can remain for years. Eventually, they get drained into the water body. 3. Some nutrients run off over the ground into the body of water. 4. The excess nutrients cause an algal bloom. 5. The algal bloom blocks the light of the sun from reaching the bottom of the water body. 6. The plants beneath the algal bloom die because they cannot get sunlight to photosynthesize. 7. Eventually, the algal bloom dies and sinks to the bottom of the lake. Bacteria begins to decompose the remains, using up oxygen for respiration. 8. The decomposition causes the water to become depleted of oxygen. Larger life forms, such as fish, suffocate to death. This body of water can no longer support life.

Cultural eutrophication

Cultural eutrophication is the process that speeds up natural eutrophication because of human activity.[7] Due to clearing of land and building of towns and cities, land runoff is accelerated and more nutrients such as phosphates and nitrate are supplied to lakes and rivers, and then to coastal estuaries and bays. Extra nutrients are also supplied by treatment plants, golf courses, fertilizers, farms (including fish farms), as well as untreated sewage in many countries.[8]

Lakes and rivers

Wfm mono lake landsat
The eutrophication of the Mono Lake which is a cyanobacteria rich Soda lake.

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. The dead algae and the organic load carried by the water inflows in to the lake settle at its bottom and undergoes anaerobic digestion releasing greenhouse gases like methane and CO2. Some part of methane gas is consumed by the anaerobic methane oxidation bacteria which in turn works as food source to the zooplankton.[9] In case the lake is not deficit of dissolved oxygen at all depths the aerobic methane oxidation bacteria like Methylococcus capsulatus can consume most of the methane by releasing CO2 which in turn aid the production of algae. Thus a self-sustaining biological process can take place to generate primary food source for the phytoplankton and zooplankton depending on availability of adequate dissolved oxygen in the water bodies which are subjected to higher organic pollution loads.[10] As algae enhances the dissolved oxygen by releasing oxygen from photosynthesis during the sunshine and consume oxygen by emitting CO2 from its respiration during the absence of sunlight, adequate dissolved oxygen availability in water bodies is very crucial for fisheries production and elimination of green house gas emissions especially during the absence of sunlight in eutrophic water bodies. The CO2 released by the algae during the absence of sunlight is stored in the water by reducing the water alkalinity and pH for its use during the sunshine.

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.[11]

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 1950 and 1995, an estimated 600,000,000 tonnes of phosphorus was applied to Earth's surface, primarily on croplands.[12]

Natural eutrophication

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.[13][14] The main difference between natural and anthropogenic eutrophication is that the natural process is very slow, occurring on geological time scales.[15]

Coastal waters

Eutrophication is a common phenomenon in coastal waters. In contrast to freshwater systems where phosphorus is often the limiting nutrient, nitrogen is more commonly the key limiting nutrient of marine waters; thus, nitrogen levels have greater importance to understanding eutrophication problems in salt water[16]. Estuaries, as the interface between freshwater and saltwater, can be both phosphorus and nitrogen limited and commonly exhibit symptoms of eutrophication. Eutrophication in estuaries often results in bottom water hypoxia/anoxia, leading to fish kills and habitat degradation[16]. 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 to coastal waters include seacage fish farming and discharges of ammonia from the production of coke from coal.

The World Resources Institute has identified 375 hypoxic coastal zones in the world, concentrated in coastal areas in Western Europe, the Eastern and Southern coasts of the US, and East Asia, particularly Japan.[17]

In addition to runoff from land, fish farming wastes and industrial ammonia discharges, atmospheric fixed nitrogen can be an important nutrient source in the open ocean. A study in 2008 found that this could account for around one third of the ocean's external (non-recycled) nitrogen supply, and up to 3% of the annual new marine biological production.[18] It has been suggested that accumulating reactive nitrogen in the environment may prove as serious as putting carbon dioxide in the atmosphere.[19]

Terrestrial ecosystems

Terrestrial ecosystems are subject to similarly adverse impacts from eutrophication.[20] Increased nitrates in soil are frequently undesirable for plants. Many terrestrial plant species are endangered as a result of soil eutrophication, such as the majority of orchid species in Europe.[21] Meadows, forests, and bogs are characterized by low nutrient content and slowly growing species adapted to those levels, so they can be overgrown by faster growing and more competitive species. 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 N2, a gaseous form of nitrogen, is very stable and unavailable directly to higher plants. Terrestrial ecosystems rely on microbial nitrogen fixation to convert N2 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.[22] This is also the case with increased levels of phosphorus. 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.[23]

Ecological effects

Caspian Sea from orbit
Eutrophication is apparent as increased turbidity in the northern part of the Caspian Sea, imaged from orbit.

Eutrophication was recognized as a water pollution problem in European and North American lakes and reservoirs in the mid-20th century.[24] Since then, it has become more widespread. Surveys showed that 54% of lakes in Asia are eutrophic; in Europe, 53%; in North America, 48%; in South America, 41%; and in Africa, 28%.[25] In South Africa, a study by the CSIR using remote sensing has shown more than 60% of the dams surveyed were eutrophic.[26] Some South African scientists believe that this figure might be higher [27] with the main source being dysfunctional sewage works that produce more than 4 billion liters a day of untreated, or at best partially treated, sewage effluent that discharges into rivers and dams.[28]

Many ecological effects can arise from stimulating primary production, but there are three particularly troubling ecological impacts: decreased biodiversity, changes in species composition and dominance, and toxicity effects.

Decreased biodiversity

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.[29] In extreme cases, anaerobic conditions ensue, promoting growth of bacteria. Zones where this occurs are known as dead zones.

New species invasion

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[30] 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.

Toxicity

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.[31] Freshwater algal blooms can pose a threat to livestock. When the algae die or are eaten, neuro- and hepatotoxins are released which can kill animals and may pose a threat to humans.[32][33] An example of algal toxins working their way into humans is the case of shellfish poisoning.[34] Biotoxins created during algal blooms are taken up by shellfish (mussels, oysters), leading to these human foods acquiring the toxicity and poisoning 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.

Sources of high nutrient runoff

Characteristics of point and nonpoint sources of chemical inputs ([12] modified from Novonty and Olem 1994)
Point sources
  • Wastewater effluent (municipal and industrial)
  • Runoff and leachate from waste disposal systems
  • Runoff and infiltration from animal feedlots
  • Runoff from mines, oil fields, unsewered industrial sites
  • Overflows of combined storm and sanitary sewers
  • Runoff from construction sites less than 20,000 m² (220,000 ft²)
  • Untreated sewage


Nonpoint sources

  • Runoff from agriculture due to fertilizers and pesticides /irrigation
  • Runoff from pasture and range
  • Urban runoff from unsewered areas
  • Septic tank leachate
  • Runoff from construction sites >20,000 m² (220,000 ft²)
  • Runoff from abandoned mines
  • Atmospheric deposition over a water surface
  • Other land activities generating contaminants

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

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 sources

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,[35][36] including the amount of development.[30] Ploughing in agriculture and development are activities that contribute most to nutrient loading. There are three reasons that nonpoint sources are especially troublesome:[23]

Soil retention

Nutrients from human activities tend to accumulate in soils and remain there for years. It has been shown[37] 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.

Runoff to surface water

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[38] or pastures. Regulations aimed at minimising nutrient exports from agriculture are typically far less stringent than those placed on sewage treatment plants[12] 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.[39]

Atmospheric deposition

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.[40] Atmospheric deposition (e.g., in the form of acid rain) can also affect nutrient concentration in water,[41] especially in highly industrialized regions.

Other causes

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.[42]

Prevention and reversal

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. Cleanup measures have been mostly, but not completely, successful. Finnish phosphorus removal measures started in the mid-1970s and have targeted rivers and lakes polluted by industrial and municipal discharges. These efforts have had a 90% removal efficiency.[43] Still, some targeted point sources did not show a decrease in runoff despite reduction efforts.

Shellfish in estuaries: unique solutions

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.[44] Filter feeding activity is considered beneficial to water quality[45] by controlling phytoplankton density and sequestering nutrients, which can be removed from the system through shellfish harvest, buried in the sediments, or lost through denitrification.[46][47] Foundational work toward the idea of improving marine water quality through shellfish cultivation was conducted by Odd Lindahl et al., using mussels in Sweden.[48] In the United States, shellfish restoration projects have been conducted on the East, West and Gulf coasts.[49] See nutrient pollution for an extended explanation of nutrient remediation using shellfish.

Seaweed farming

Seaweed (kelp, ...) also absorbs phosphorus and nitrogen[50] and is thus useful to remove nutrients from overfertilised parts of the sea.[51]

Minimizing nonpoint pollution: future work

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.

Riparian buffer zones

Studies show that intercepting non-point pollution between the source and the water is a successful means of prevention.[12] Riparian buffer zones are interfaces between a flowing body of water and land, and have been created near waterways in an attempt to filter pollutants; sediment and nutrients are deposited here instead of in water. Creating buffer zones near farms and roads is another possible way to prevent nutrients from traveling too far. Still, studies have shown[52] 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.

Prevention policy

Laws regulating the discharge and treatment of sewage have led to dramatic nutrient reductions to surrounding ecosystems,[23] 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.[53] Thus, it is not unreasonable to command livestock owners to clean up animal waste—which when left stagnant will leach into ground water.

Policy concerning the prevention and reduction of eutrophication can be broken down into four sectors: Technologies, public participation, economic instruments, and cooperation.[54] The term technology is used loosely, referring to a more widespread use of existing methods rather than an appropriation of new technologies. 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.[55] Waste disposal technology constitutes another factor in eutrophication prevention. 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.[56] The technology to safely and efficiently reuse waste water, both from domestic and industrial sources, should be a primary concern for policy regarding eutrophication.

The role of the public is a major factor for the effective prevention of eutrophication. In order for a policy to have any effect, the public must be aware of their contribution to the problem, and ways in which they can reduce their effects. Programs instituted to promote participation in the recycling and elimination of wastes, as well as education on the issue of rational water use are necessary to protect water quality within urbanized areas and adjacent water bodies.

Economic instruments, "which include, among others, property rights, water markets, fiscal and financial instruments, charge systems and liability systems, are gradually becoming a substantive component of the management tool set used for pollution control and water allocation decisions."[54] Incentives for those who practice clean, renewable, water management technologies are an effective means of encouraging pollution prevention. By internalizing the costs associated with the negative effects on the environment, governments are able to encourage a cleaner water management.

Because a body of water can have an effect on a range of people reaching far beyond that of the watershed, cooperation between different organizations is necessary to prevent the intrusion of contaminants that can lead to eutrophication. Agencies ranging from state governments to those of water resource management and non-governmental organizations, going as low as the local population, are responsible for preventing eutrophication of water bodies. In the United States, the most well known inter-state effort to prevent eutrophication is the Chesapeake Bay.[57]

Nitrogen testing and modeling

Soil Nitrogen Testing (N-Testing) is a technique that helps farmers optimize the amount of fertilizer applied to crops. By testing fields with this method, farmers saw a decrease in fertilizer application costs, a decrease in nitrogen lost to surrounding sources, or both.[58] By testing the soil and modeling the bare minimum amount of fertilizer are needed, farmers reap economic benefits while reducing pollution.

Organic farming

There has been a study that found that organically fertilized fields "significantly reduce harmful nitrate leaching" over conventionally fertilized fields.[59] However, a more recent study found that eutrophication impacts are in some cases higher from organic production than they are from conventional production.[60]

Dredging

Dredging helps in reduction of soil contamination that was caused by sewage sludge (like fecal sludge), wilted plants, or chemical spill.

Geo-engineering in lakes

Application of a phosphorus sorbent to a lake - The Netherlands
Application of a phosphorus sorbent to a lake - The Netherlands

Geo-engineering is the manipulation of biogeochemical process, mainly phosphorus cycle, to achieve a desire an ecological response in the ecosystem [61]. Geo-engineering technique typically uses materials able to chemically inactivate the phosphorus available for the organism (i.e. phosphate) in the water column and also block the phosphate release from the sediment (internal loading) [62]. Phosphate is one of the main contributing factors to algal growth, mainly cyanobacteria, so once phosphate is reduced the algal is not able to overgrowth [63]. Thus, geo-engineering materials is used to speed-up the recovery of eutrophic water bodies and manage algal bloom [64]. There are several phosphate sorbents in the literature, from metal salts (e.g. Alum, aluminium sulphate[65]), minerals, natural clays and local soils, industrial waste products, modified clays (e.g.Lanthanum modified bentonite) and others. [66] [67]. The phosphate sorbent is commonly applied in the surface of the water body and it sinks to the bottom of the lake reducing phosphate, such sorbents have been applied worldwide to manage eutrophication and algal bloom [68] [69] [70] [71] [72] [73].

See also

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Ammersee kilch

The Ammersee kilch (Coregonus bavaricus) is a species of freshwater whitefish endemic to Lake Ammersee in the German state of Upper Bavaria. A small, silver-colored fish, it typically lives between 60–85 m (197–279 ft) deep, though shallower in the summer months. In the early 20th century the Ammersee kilch was an important commercial species, but its population declined drastically in the 1930s onward due to overfishing and eutrophication of the only lake in which it is found. Today it is listed as Critically Endangered by the International Union for the Conservation of Nature (IUCN) and may be on the verge of extinction.

Anoxic waters

Anoxic waters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen and are a more severe condition of hypoxia. The US Geological Survey defines anoxic groundwater as those with dissolved oxygen concentration of less than 0.5 milligrams per litre. This condition is generally found in areas that have restricted water exchange.

In most cases, oxygen is prevented from reaching the deeper levels by a physical barrier as well as by a pronounced density stratification, in which, for instance, heavier hypersaline waters rest at the bottom of a basin. Anoxic conditions will occur if the rate of oxidation of organic matter by bacteria is greater than the supply of dissolved oxygen.

Anoxic waters are a natural phenomenon, and have occurred throughout geological history. In fact, some postulate that the Permian–Triassic extinction event, a mass extinction of species from world's oceans, resulted from widespread anoxic conditions. At present anoxic basins exist, for example, in the Baltic Sea, and elsewhere (see below). Recently, there have been some indications that eutrophication has increased the extent of the anoxic zones in areas including the Baltic Sea, the Gulf of Mexico, and Hood Canal in Washington State.

Coregonus confusus

Coregonus confusus is a freshwater whitefish from Switzerland. It is also known by its native Swiss German common name, spelled pfärrit, pfarrig, and pfärrig. It was described as Coregonus annectens confusus by Victor Fatio in 1885 from syntypes which have been lost in 1902. The species is rare and only known with certainty from Lake Biel. There is also a possibility that it might occur in Lake Neuchâtel. It vanished from Lake Murten in the 1960s due to eutrophication and water level management.

Coregonus vandesius

Coregonus vandesius, the vendace, is a freshwater whitefish found in the United Kingdom. Population surveys since the 1960s have revealed a steady decline and the fish is no longer present in some of its previous haunts but is still present in Bassenthwaite Lake and Derwent Water. The main threats it faces are eutrophication and the introduction of alien species of fish which eat its eggs and fry. The International Union for Conservation of Nature has rated its conservation status as "endangered".

Cultural eutrophication

Cultural eutrophication is the process that speeds up natural eutrophication because of human activity. Due to clearing of land and building of towns and cities, land runoff is accelerated and more nutrients such as phosphates and nitrate are supplied to lakes and rivers, and then to coastal estuaries and bays. Extra nutrients are also supplied by treatment plants, golf courses, and agricultural practices through the use of fertilizers. Human activities, including the ones previously listed, can be responsible for an increase in nutrients, therefore, cultural eutrophication is more pronounced in non-polar ecosystems which have higher levels of human activity. Polar regions have less human activity and subsequently less cultural eutrophication.

One response to added amounts of nutrients in the aquatic ecosystem is the rapid growth of microscopic algae, also known as an algal bloom. In freshwater systems, the formation of floating algal blooms are commonly nitrogen-fixing cyanobacteria (blue-green algae). This outcome is favoured when nitrogen inputs are reduced and phosphorus inputs are increased.

Large amounts of algae reduce the amount of dissolved oxygen available in the water for other organisms, which increases fish mortality rates. These areas affected by algal blooms are known as dead zones, and are found where rivers empty into oceans. Nutrient pollution is a major cause of algal blooming however, the excess nutrients also facilitate the growth of other aquatic plants. Following this, overcrowding occurs and plants compete for sunlight, space, and oxygen. Overgrowth of water plants also blocks sunlight and oxygen for aquatic life in the water, which threatens their survival. Increased competition for the added nutrients can cause potential disruption to entire ecosystems and food webs, as well as a loss of habitat, and biodiversity of species.The Experimental Lakes Area (ELA), Ontario, Canada is a fully equipped, year-round, permanent field station that uses the whole ecosystem approach and long-term, whole-lake investigations of freshwater focusing on cultural eutrophication. ELA is currently cosponsored by the Canadian Departments of Environment and Fisheries and Oceans, with a mandate to investigate the aquatic effects of a wide variety of stresses on lakes and their catchments.

Eustrongylidosis

Eustrongylidosis is a parasitic disease that mainly affects wading birds worldwide; however, the parasite’s complex, indirect life cycle involves other species such as aquatic worms and fish. Moreover, this disease is zoonotic which means the parasite can transmit disease from animals to humans. Eustrongylidosis is named after the causative agent Eustrongylides and typically occurs in eutrophicated waters where concentrations of nutrients and minerals are high enough to provide ideal conditions for the parasite to thrive and persist. Because eutrophication has become a common issue due to agricultural runoff and urban development, cases of Eustrongylidosis are becoming prevalent and hard to control. Eustrongylidosis can be diagnosed before or after death by observing behavior, clinical signs and performing fecal flotations and necropsies. Methods to control Eustrongylidosis include preventing eutrophication and providing hosts with uninfected food sources in aquaculture farms. Parasites are known to be indicators of environmental health and stability and should therefore be studied further to better understand the parasite’s life cycle and how it affects predator-prey interactions and improve conservation efforts.

Hardy Pond

Hardy Pond is a 45-acre (180,000 m2) pond located in Waltham, Massachusetts. Originally almost twice the size, in recent times the pond level was lowered in an inappropriate approach to controlling flooding. The quality of the water has degraded due to eutrophication caused by run-off from roads, fertilizers, and storm drain inputs. The pond is contiguous with 35 acres (140,000 m2) of adjoining wetlands. It is a popular site for bird sightings, with over 140 species listed.

Human impact on the nitrogen cycle

Human impact on the nitrogen cycle is diverse. Agricultural and industrial nitrogen (N) inputs to the environment currently exceed inputs from natural N fixation. As a consequence of anthropogenic inputs, the global nitrogen cycle (Fig. 1) has been significantly altered over the past century. Global atmospheric nitrous oxide (N2O) mole fractions have increased from a pre-industrial value of ~270 nmol/mol to ~319 nmol/mol in 2005. Human activities account for over one-third of N2O emissions, most of which are due to the agricultural sector. This article is intended to give a brief review of the history of anthropogenic N inputs, and reported impacts of nitrogen inputs on selected terrestrial and aquatic ecosystems.

Hydrobiology

Hydrobiology is the science of life and life processes in water. Much of modern hydrobiology can be viewed as a sub-discipline of ecology but the sphere of hydrobiology includes taxonomy, economic biology, industrial biology, morphology, physiology etc. The one distinguishing aspect is that all relate to aquatic organisms. Much work is closely related to limnology and can be divided into lotic system ecology (flowing waters) and lentic system ecology (still waters).

One of the significant areas of current research is eutrophication. Special attention is paid to biotic interactions in plankton assemblage including the microbial loop, the mechanism of influencing water blooms, phosphorus load and lake turnover. Another subject of research is the acidification of mountain lakes. Long-term studies are carried out on changes in the ionic composition of the water of rivers, lakes and reservoirs in connection with acid rain and fertilisation. One goal of current research is elucidation of the basic environmental functions of the ecosystem in reservoirs, which are important for water quality management and water supply.

Much of the early work of hydrobiologists concentrated on the biological processes utilised in sewage treatment and water purification especially slow sand filters. Other historically important work sought to provide biotic indices for classifying waters according to the biotic communities that they supported. This work continues to this day in Europe in the development of classification tools for assessing water bodies for the EU water framework directive.

Jakarta Bay

Jakarta Bay (Indonesian: Teluk Jakarta) is a bay north of North Jakarta city. The Thousand Islands are located in Jakarta Bay. 13 rivers flow into the bay. The majority of the bay's coastal communities consist of people living below the poverty line, in conditions of poor sanitation. Nutrient inputs from agricultural runoff, industrial pollution, and wastewater have led to eutrophication, which in turn led to changes in the area's biodiversity. Harmful algal blooms have been observed.

Lort River

Lort River is a river located in the Goldfields-Esperance region and the Eastern Mallee sub-region of Western Australia.

The headwaters of the Lort River begin in the Peak Charles National Park and its surrounding vacant Crown land. The river flows in a south-westerly direction and enters farmland area for a distance of 45 kilometres (28 mi) with a reserve that is an average of 500 metres (1,640 ft) wide containing riparian vegetation. The river then enters the Stokes National Park before discharging into Stokes Inlet.

Both the river and the inlet were named by John Septimus Roe while exploring and surveying the area in 1848 after his friend Admiral John Lort Stokes.The catchment of the river has been extensively cleared for Agricultural purposes. It is estimated that 60% of the catchment has been cleared; this has led to increased sedimentation, eutrophication and salinity levels of the river.

Multi-effect Protocol

The 1999 Gothenburg Protocol to Abate Acidification, Eutrophication and Ground-level Ozone (known as the Multi-effect Protocol or the Gothenburg Protocol) is a multi-pollutant protocol designed to reduce acidification, eutrophication and ground-level ozone by setting emissions ceilings for sulphur dioxide, nitrogen oxides, volatile organic compounds and ammonia to be met by 2010. As of August 2014, the Protocol had been ratified by 26 parties, which includes 25 states and the European Union.The Protocol is part of the Convention on Long-Range Transboundary Air Pollution. The Convention is an international agreement to protect human health and the natural environment from air pollution by control and reduction of air pollution, including long-range transboundary air pollution.

The geographic scope of the Protocol includes Europe, North America and countries of Eastern Europe, Caucasus and Central Asia (EECCA).

On May 4, 2012, at a meeting at the United Nations Office at Geneva, the Parties to the Gothenburg Protocol agreed on a substantial number of revisions, most important are the inclusion of commitments of the Parties to further reduce their emissions until 2020. These amendments now need to be ratified by Parties in order to make them binding.

Nutrient pollution

Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from septic tanks and feedlots, and emissions from combustion. Excess nutrients have been summarized as potentially leading to:

Population effects: excess growth of algae (blooms);

Community effects: species composition shifts (dominant taxa);

Ecological effects: food web changes, light limitation;

Biogeochemical effects: excess organic carbon (eutrophication); dissolved oxygen deficits (environmental hypoxia); toxin production;

Human health effects: excess nitrate in drinking water (blue baby syndrome); disinfection by-products in drinking water;

Biodiversity effects: excessive algae blooms (biodiversity loss).In a 2011 United States Environmental Protection Agency (EPA) report, the agency's Science Advisory Board succinctly stated: “Excess reactive nitrogen compounds in the environment are associated with many large-scale environmental concerns, including eutrophication of surface waters, toxic algae blooms, hypoxia, acid rain, nitrogen saturation in forests, and global warming.”

Oreti River

The Oreti River is one of the main rivers of Southland, New Zealand, and is 170 kilometres (110 mi) long. The river has been identified as an Important Bird Area by BirdLife International because, for much of its length, it supports breeding colonies of black-billed gulls.The Oreti has its headwaters close to the Mavora Lakes between Lake Te Anau and Lake Wakatipu, and flows south across the Southland Plains to its outflow into Foveaux Strait at the southeastern end of Oreti Beach. En route, it runs through the towns of Lumsden and Winton, before passing through the city of Invercargill, close to the river's estuary.

For the final part of the river's length, around the city of Invercargill and the river's estuary just south of the city, it is known as the New River, a name occasionally encountered to refer to the whole river. It shares this estuary with several smaller rivers, most notably the Waihopai River.

The New River Estuary, which meets the end of the Oreti River before it reaches the sea, is in decline. Recent science reports show that regions of the upper estuary are under stress and showing eutrophication. There is excessive macroalgal growth including sediment quality decline and high concentrations of chlorophyll-a in the water column. Chlorophyll-a was used as an indicator of eutrophic conditions in the water column, and is a colour pigment present in many types of algae that can give an indication of how much algae is present in the water column.The Invercargill Rowing Club relocated to the river in 1958.

Phosphorus cycle

The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth. The production of phosphine gas occurs in only specialized, local conditions. Therefore, the phosphorus cycle should be viewed from whole Earth system and then specifically focused on the cycle in terrestrial and aquatic systems.

On the land, phosphorus gradually becomes less available to plants over thousands of years, since it is slowly lost in runoff. Low concentration of phosphorus in soils reduces plant growth, and slows soil microbial growth - as shown in studies of soil microbial biomass. Soil microorganisms act as both sinks and sources of available phosphorus in the biogeochemical cycle. Locally, transformations of phosphorus are chemical, biological and microbiological: the major long-term transfers in the global cycle, however, are driven by tectonic movements in geologic time.Humans have caused major changes to the global phosphorus cycle through shipping of phosphorus minerals, and use of phosphorus fertilizer, and also the shipping of food from farms to cities, where it is lost as effluent.

Preston River

The Preston River is a river in the South West region of Western Australia.

The river has a total length of 84 kilometres (52 mi) and rises near Goonac siding then flows in a north-westerly direction until discharging into the Leschenault Estuary.

The headwaters are 80 kilometres (50 mi) inland within the Darling Range and run across the Blackwood Plateau and the Swan Coastal Plain.

The majority of the river catchment has been cleared for agriculture although some remnant forest vegetation exists at the headwaters.

The towns of Donnybrook and Boyanup are on the shores of the Preston River.

The major tributaries of the river include the Ferguson River and Joshua Creek. Minor tributaries include Thomson Brook, Crooked Brook, Charley Creek, Waterfall Gully, Mininup Brook, Millbrook and Gavin Guly. The Glen Mervyn Dam is along the Preston River.

The river basin is monitored routinely as a result of eutrophication problems within the Leschenault Inlet. The water quality is fresh in many places and generally low in nutrients although some areas are slightly enriched with nitrogen.

Sodium triphosphate

Sodium triphosphate (STP), also sodium tripolyphosphate (STPP), or tripolyphosphate (TPP),) is an inorganic compound with formula Na5P3O10. It is the sodium salt of the polyphosphate penta-anion, which is the conjugate base of triphosphoric acid. It is produced on a large scale as a component of many domestic and industrial products, especially detergents. Environmental problems associated with eutrophication are attributed to its widespread use.

The Broads

The Broads (known for marketing purposes as The Broads National Park) is a network of mostly navigable rivers and lakes in the English counties of Norfolk and Suffolk. The lakes, known as broads, were formed by the flooding of peat workings. The Broads, and some surrounding land, were constituted as a special area with a level of protection similar to a national park by the Norfolk and Suffolk Broads Act 1988. The Broads Authority, a special statutory authority responsible for managing the area, became operational in 1989.The area is 303 square kilometres (117 sq mi), most of which is in Norfolk, with over 200 kilometres (120 mi) of navigable waterways. There are seven rivers and 63 broads, mostly less than 4 metres (13 ft) deep. Thirteen broads are generally open to navigation, with a further three having navigable channels. Some broads have navigation restrictions imposed on them in autumn and winter, although the legality of the restrictions is questionable.Although the terms Norfolk Broads and Suffolk Broads are used to identify specific areas within the two counties respectively, the whole area is frequently referred to as the "Norfolk Broads". The Broads has similar status to the national parks in England and Wales; the Broads Authority has powers and duties akin to the national parks, but is also the third-largest inland navigation authority. Because of its navigation role the Broads Authority was established under its own legislation on 1 April 1989. The Broads Authority Act 2009, which was promoted through Parliament by the authority, is intended to improve public safety on the water.

Xenophagy

Xenophagy (Greek "strange" + "eating") and allotrophy (Greek "other" + "nutrient") are changes in established patterns of biological consumption, by individuals or groups.

• In entomology, xenophagy is a categorical change in diet, such as an herbivore becoming carnivorous, a predator becoming necrophagous, a coprophage becoming necrophagous or carnivorous, or a reversal of such changes. Allotrophy is a less extreme change in diet, such as in the case of the seven-spot ladybird, which can diversify a diet of aphids to sometimes include pollen. There are several apparent cases of allotrophy in Israeli Longitarsus beetles.• In microbiology, xenophagy is the process by which a cell directs autophagy against pathogens, as reflected in the study of antiviral defenses. Cellular xenophagy is an innate component of immune responses, though the general importance of xenophagy is not yet certain.• In ecology, allotrophy is also reflected in eutrophication, being a change in nutrient source such as an aquatic ecosystem that starts receiving new nutrients from drainage of the surrounding land.

Aquatic ecosystems
Air pollution
Water pollution
Soil contamination
Radioactive contamination
Other types of pollution
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