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

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 fishes cannot live below 30% DO saturation. A "healthy" aquatic environment should seldom experience DO less than 80%. 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. ... Jump to: navigation, search Statistics State: Schleswig-Holstein District: Independent city Area: 113. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Oxygen saturation is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. ... For other uses of the word underwater, see Underwater (disambiguation) An underwater scene just beneath the surface Underwater, sometimes shortened as U/W, is a term describing the realm below the surface of water where the water exists in a natural feature (called a body of water) such as an... Anaerobic is a technical word which literally means without air. ... A reducing environment is one chacterized by little or no free oxygen (dissolved or as a gas). ...

Causes of oxygen depletion

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 a highly detrimental 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. Pollution is the release of harmful environmental contaminants, or the substances so released. ... Jump to: navigation, search 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. ... Jump to: navigation, search Diagrams of some typical phytoplankton Phytoplankton refers to the autotrophic component of the plankton that drifts in the water column. ... A red tide resulting from a dinoflagellate bloom discoloring the water on the right 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. ... WORM means Write Once, Read Many. ... CLAMS Maxima clam (Tridacna maxima) Clams are shelled marine or freshwater molluscs belonging to the class Bivalvia. ...

Underwater video frame of the sea floor covered with dead or dying crabs, fish and clams attributed to oxygen depletion

A graphic (below, left) shows oxygen depletion in the open ocean, a consequence of too much input of oxygen consuming chemicals and bioactive nutrients from the Hudson, Raritan, and Mullica rivers into the Atlantic Ocean off New York and Atlantic City, New Jersey, USA. 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. ... Jump to: navigation, search The worlds oceans as seen from the South Pole Ocean (from Okeanos, a Greek god of sea and water; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth, and nearly half of the worlds marine waters are over 3000 m deep. ... Hudson may refer to: Hudson Bay, a body of water in northern Canada Hudson River, a river in the eastern U.S. Mount Hudson, a volcano in Chile Hudsons Bay, a 1940 film Hudson Soft, a Japanese video game developer Hudson Motor Car, an automobile manufacturing company Lockheed Hudson... The Raritan people were a tribe of Lenape Indians who inhabited the areas around the present Raritan Bay in northern New Jersey and Staten Island, New York. ... Mullica Township is a township located in Atlantic County, New Jersey. ... Jump to: navigation, search State nickname: The Empire State Other U.S. States Capital Albany Largest city New York City Governor George Pataki (R) Senators Charles Schumer (D) Hillary Rodham Clinton (D) Official languages None (English is de facto) Area 141,205 km² (27th)  - Land 122,409 km²  - Water 18... Alternate meanings: See Atlantic City (disambiguation) Atlantic City is a city located in USA. As of the 2000 census, the city had a total population of 40,517. ... Jump to: navigation, search State nickname: The Garden State Other U.S. States Capital Trenton Largest city Newark Governor Richard Codey (D) Acting Senators Jon Corzine (D) Frank Lautenberg (D) Official languages None defined Area 22,608 km² (47th)  - Land 19,231 km²  - Water 3,378 km² (14. ...

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. 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. ... 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.

Oxygen-depleted areas are in red

Oxygen depletion

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. Download high resolution version (770x740, 20 KB)oxygen depletion map ocean File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Download high resolution version (770x740, 20 KB)oxygen depletion map ocean File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Jump to: navigation, search Image File history File links Oxygen_depletion. ... Jump to: navigation, search 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. ... ... Sunset at sea Look up Sea on Wiktionary, the free dictionary Look up maritime in Wiktionary, the free dictionary. ... Behavior (or behaviour) refers to the actions or reactions of an object or organism, usually in relation to the environment. ... Jump to: navigation, search Groups Conodonta Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi (early jawless fish) Thelodonti Anaspida Cephalaspidomorphi (early jawless fish) Galeaspida Pituriaspida Osteostraci Gnathostomata (jawed vertebrates) Placodermi Chondrichthyes (cartilaginous fish) Acanthodii Osteichthyes (bony fish) Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) A fish is a poikilothermic... 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. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

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
• Oxygen saturation
• Winkler test for dissolved oxygen — for instructions on how to determine the amount of oxygen dissolved in fresh water.

An anoxic event occurs when the Earths oceans become completely depleted of O2 below the surface levels. ... This page is about the oceanic phenomenon; see The Dead Zone for the novel by Stephen King. ... Oxygen saturation is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. ... The Winkler test is used to determine the level of dissolved oxygen in fresh water samples. ...

External link

• Hypoxia in the Gulf of Mexico