It has been suggested that Anoxic sea water, Oxygen minimum zone, and Hypoxic zone be merged into this article or section. (Discuss)

For other uses of the term "hypoxia", see hypoxia.

Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments as dissolved oxygen (DO; molecular oxygen dissolved in the water) becomes reduced in concentration to a point detrimental to aquatic organisms living in the system. Dissolved oxygen is typically expressed as a percentage of the oxygen that would dissolve in the water at the prevailing temperature and salinity (both of which affect the solubility of oxygen in water; see oxygen saturation and underwater). An aquatic system lacking dissolved oxygen (0% saturation) is termed anaerobic, reducing, or anoxic; a system with low DO concentration—in the range between 1 and 30% DO saturation—is called hypoxic. Most fish cannot live below 30% DO saturation. A "healthy" aquatic environment should seldom experience DO less than 80%. Image File history File links Please see the file description page for further information. ... Anoxic sea water refers to water depleted of oxygen. ... This page is about the oceanic phenomenon; see The Dead Zone for the novel by Stephen King. ... Pollution is the release of environmental contaminants. ... Before flue gas desulfurization was installed, the emissions from this power plant in New Mexico contained excessive amounts of sulfur dioxide. ... Acid rain (or more accurately acid precipitation)[1] occurs when sulfur dioxide and nitrogen oxides are emitted into the atmosphere, undergo chemical transformations and are absorbed by water droplets in clouds. ... An air quality measurement station in Edinburgh, Scotland The Air Quality Index (AQI) is a standardized indicator of the air quality in a given location. ... Atmospheric dispersion modeling is performed with computer programs that use mathematical equations and algorithms to simulate how pollutants in the ambient atmosphere disperse in the atmosphere. ... 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Aerosol pollution over Northern India and Bangladesh - Photo: NASA Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid (a smoke) or liquid (an aerosol) suspended in a gas. ... Victorian London was notorious for its thick smogs, or pea-soupers, a fact that is often recreated to add an air of mystery to a period costume drama. ... Roadway air dispersion is applied to highway segments Roadway air dispersion modeling is the study of air pollutant transport from a roadway or other linear emitter. ... Water pollution Water pollution is a large set of adverse effects upon water bodies (lakes, rivers, oceans, groundwater) caused by human activities. ... Eutrophication is apparent as increased turbidity in the northern part of the Caspian Sea, imaged from orbit. ... Pumping of highly toxic (dark black) sludge, much seeps back into the ocean in the form of particles. ... Ocean acidification is the name given to the ongoing decrease in the pH of the Earths oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. ... Volunteers cleaning up the aftermath of the Prestige oil spill An oil spill(also called a oil slick) is the unintentional release of oil (generally, petroleum) into the natural environment as a result of human activity. ... Ships can pollute the waterways and oceans in many ways. ... Runoff flowing into a stormwater drain Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component of the water cycle[1][2]. Runoff that occurs on surfaces before reaching a channel is also called overland flow. ... Fishkill from receiving waters Thermal pollution is a temperature change in natural water bodies caused by human influence. ... Wastewater is any water that has been adversely affected in quality by anthropogenic influence. ... Waterborne diseases, according to the World Health Organization, are those which generally arise from the contamination of water by feces or urine, infected by pathogenic viruses or bacteria, and which are directly transmitted when unsafe water is drunk or used in the preparation of food. ... Water quality is the chemical and physical characterization of water. ... Water stagnation occurs when water stops flowing. ... Excavation of leaking underground storage tank causing soil contamination Soil contamination is the presence of man made chemicals or other alteration to the natural soil environment. ... Bioremediation can be defined as any process that uses microorganisms, fungi, green plants or their enzymes to return the environment altered by contaminants to its original condition. ... This article or section does not cite its references or sources. ... A cropduster spreading pesticide. ... The radiation warning symbol (trefoil). ... 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A Clean Air Act describes one of a number of pieces of legislation relating to the reduction of smog and atmospheric pollution in general. ... The Clean Water Act, 33 U.S.C.A. § 1251 et seq. ... Kyoto Protocol Opened for signature December 11, 1997 in Kyoto, Japan Entered into force February 16, 2005. ... This act gave authority to Surgeon General to make programs to reduce or eliminate water pollution in rivers, underground rivers, and other waterways. ... This is a list of environmental organizations, organizations that preserve, analyze or monitor the environment in different ways. ... The Department for Environment, Food and Rural Affairs (Defra) is the United Kingdom government department responsible for environmental protection, food production and standards, agriculture, fisheries and rural communities. ... EPA redirects here. ... Global Atmosphere Watchs logo The Global Atmosphere Watch (GAW) is a worldwide system established by the World Meteorological Organization – a United Nations agency – to monitor trends in the Earths atmosphere. ... This article is becoming very long. ... The National Ambient Air Quality Standards (NAAQS) are standards established by the United States Environmental Protection Agency that apply for outdoor air throughout the country. ... This article does not cite its references or sources. ... Hypoxia may refer to: Hypoxia (medical), the lack of oxygen in tissues Hypoxia or Oxygen depletion, a reduced concentration of dissolved oxygen in a water body leading to stress or even death in aquatic organisms This is a disambiguation page: a list of articles associated with the same title. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... Oxygen saturation is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. ... An underwater scene just beneath the surface. ... A reducing environment is one chacterized by little or no free oxygen (dissolved or as a gas). ...

Causes of hypoxia

Decline of oxygen saturation to anoxia, measured during the night in Kiel Fjord, Germany. Depth = 5 m

Oxygen depletion could be the result of a number of factors including natural ones, but is of most concern as a consequence of pollution and as an outcome of a process known as eutrophication. Where plant nutrients enter a river, lake, or ocean, phytoplankton blooms are encouraged. While phytoplankton, through photosynthesis, will raise DO saturation during daylight hours, the dense population of a bloom reduces DO saturation during the night. When phytoplankton cells die, they sink towards the bottom and are decomposed by bacteria, a process that further reduces DO in the water column. If oxygen depletion progresses to hypoxia, fish kills can occur and invertebrates like worms and clams on the bottom may be killed as well. oxygen depletion 1 graphic Uwe Kils GFDL File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... oxygen depletion 1 graphic Uwe Kils GFDL File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Kiel ( ) is a city in northern Germany and the capital of the Bundesland Schleswig-Holstein. ... Pollution is the release of environmental contaminants. ... Eutrophication is apparent as increased turbidity in the northern part of the Caspian Sea, imaged from orbit. ... Nutrients and the body A nutrient is any element or compound necessary for or contributing to an organisms metabolism, growth, or other functioning. ... Diagrams of some typical phytoplankton Phytoplankton are the autotrophic component of the plankton that drift in the water column. ... An algal bloom is a relatively rapid increase in the population of (usually) phytoplankton algae in an aquatic system. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Earthworm A worm is an elongated soft-bodied invertebrate animal. ... Littleneck clams: Rocks with food inside. ...

Still frame from an underwater video of the sea floor. The floor is covered with crabs, fish, and clams apparently dead or dying from oxygen depletion.

Natural occurrences of hypoxia have been observed. Water flowing from a river into the sea is less dense than salt water. When this water does not mix with the underlying saline water, the oxygen concentration in the bottom layer may become low enough for hypoxia to occur. Hypoxia is particularly problematic in shallow waters of semi-enclosed bodies of water like the Waddenzee or the Gulf of Mexico where land runoff is substantial. In these areas, a so-called "dead zone" can be created. fishkill Baltic - image Uwe Kils GFDL File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... fishkill Baltic - image Uwe Kils GFDL File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The Wadden Sea (Wattenmeer in German, Waddenzee in Dutch, Waadsee in Frisian, Wattensee in Low Saxon, Vadehavet in Danish) is the name for a body of water and its associated coastal wetlands lying between a section of the coast of northwestern continental Europe and the North Sea. ... Gulf of Mexico in 3D perspective. ... This page is about the oceanic phenomenon; see The Dead Zone for the novel by Stephen King. ...

Solutions

To combat hypoxia, it is essential to reduce the amount of land-derived nutrients reaching rivers in runoff. Defensively this can be done by improving sewage treatment and by reducing the amount of fertilizers leaching into the rivers. Offensively this can be done by restoring natural environments along a river; marshes are particularly effective in reducing the amount of phosphorus and nitrogen (nutrients) in water.

Graphs of oxygen and salinity levels at Kiel Fjord in September 1998.

In a very short time the oxygen saturation can drop to zero when offshore blowing winds drive surface water out and anoxic depthwater rises up. At the same time a decline in temperature and a rise in salinity is observed (from the longterm ecological observatory in the seas at Kiel Fjord, Germany). New approaches of longterm monitoring of oxygen regime in the ocean observe online the behavior of fish and zooplankton, which changes drastically under reduced oxygen saturations (ecoSCOPE) and already at very low levels of water pollution. Image File history File links Oxygen_depletion. ... Image File history File links Oxygen_depletion. ... Oxygen saturation is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. ... ... Sea as seen from jetty in Frankston, Australia Look up maritime in Wiktionary, the free dictionary. ... For the Pet Shop Boys album of the same name see Behaviour Behavior or behaviour (see spelling differences) refers to the actions or reactions of an object or organism, usually in relation to the environment. ... A giant grouper at the Georgia Aquarium Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. ... Photomontage of plankton organisms Plankton is the aggregate community of weakly swimming but mostly drifting small organisms that inhabit the water column of the ocean, seas, and bodies of freshwater. ... Oxygen saturation is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. ... This article needs cleanup. ... Water pollution Water pollution is a large set of adverse effects upon water bodies (lakes, rivers, oceans, groundwater) caused by human activities. ...

Bog chemistry

In certain northern European sphagnum acidic bogs, a condition of hypoxia arises that prevents tissue decay by impeding micro-organisms in the soil and groundwater. Remarkable preservation of human mummies has occurred in some cases such as the discovery of Haraldskær Woman and Tollund Man in Jutland, Denmark. Species See text. ... Haraldskær Woman in glass covered coffin, Velje, Denmark The Haraldskær Woman (or Haraldskaer Woman) is a well-preserved Iron Age bog body naturally preserved in a bog in Jutland, Denmark. ... Tollund man. ... Jutland Peninsula Jutland (Danish: Jylland; German: Jütland; Frisian Jutlân; Low German Jötlann) is a peninsula in northern Europe that forms the only non-insular part of Denmark and also the northernmost part of Germany, dividing the North Sea from the Baltic Sea. ...

References

• Kils, U., U. Waller, and P. Fischer. 1989. The Fish Kill of the Autumn 1988 in Kiel Bay. International Council for the Exploration of the sea C M 1989/L:14
• Fischer P. and U. Kils. 1990. In situ Investigations on Respiration and Behaviour of Stickleback Gasterosteus aculeatus and the Eelpout Zoaraes viviparus During Low Oxygen Stress. International Council for the Exploration of the Sea C M 1990/F:23
• Fischer P., K. Rademacher, and U. Kils. 1992. In situ investigations on the respiration and behaviour of the eelpout Zoarces viviparus under short term hypoxia. Mar Ecol Prog Ser 88: 181-184

See also

• Anoxic event
• Dead zone (ecology)
• Dead zone in front of Atlantic City
• Oxygen saturation
• Wastewater quality indicators discusses both BOD and COD as measures of water quality.
• Winkler test for dissolved oxygen — for instructions on how to determine the amount of oxygen dissolved in fresh water.

Oceanic Anoxic Events occur when the Earths oceans become completely depleted of O2 below the surface levels. ... It has been suggested that this article or section be merged into Hypoxia (environmental). ... Oxygen saturation is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. ... Wastewater quality indicators such as the Biochemical oxygen demand (BOD) and the Chemical oxygen demand (COD) are essentially laboratory test measures of the amount of oxygen in a wastewater. ... Look up bod in Wiktionary, the free dictionary. ... Species Gadus morhua Gadus macrocephalus Gadus ogac Cod is the common name for the genus Gadus of fish, belonging to the family Gadidae, and is also used in the common name of a variety of other fishes. ... The Winkler test is used to determine the level of dissolved oxygen in fresh water samples. ...

External link

• Hypoxia in the Gulf of Mexico