Oxygen minimum zone


Oxygen minimum zone

The Oxygen minimum zone (OMZ), sometimes referred to as the shadow zone, is the zone in which oxygen saturation in seawater in the ocean is at its lowest. This zone occurs at depths of about 200 to 1,000 metres, depending on local circumstances.

Surface ocean waters generally have oxygen concentrations close to equilibrium with the Earth's atmosphere. In general, colder waters hold more oxygen than warmer waters. As this water moves out of the mixed layer into the thermocline it is exposed to a rain of organic matter from above. Aerobic bacteria feed on this organic matter; oxygen is used as part of the bacterial metabolic process lowering its concentration within the water. Therefore, the concentration of oxygen in deep water is dependent on the amount of oxygen it had when it was at the surface minus depletion by deep sea organisms.

The downward flux of organic matter decreases sharply with depth, with 80-90% being consumed in the top 1000m. The deep ocean thus has higher oxygen because rates of oxygen consumption are low compared with the supply of cold, oxygen-rich deep waters from polar regions. In the surface layers, oxygen is supplied by exchange with the atmosphere. Depths in between, however, have higher rates of oxygen consumption and (as discussed below) lower rates of advective supply of oxygen-rich waters.

The distribution of the open-ocean oxygen minimum zones is controlled by the large-scale ocean circulation. Essentially, waters that are part of the wind-driven subtropical gyre circulations are rapidly exchanged with the surface and never acquire a strong oxygen deficit. However, along the equatorial edge of the gyres, one finds a stagnant pool of water which has no direct connection to the ocean surface. As a result these "shadow zones" have very low oxygen concentrations-even though in regions such as the Eastern Tropical North Pacific there may be relatively little organic matter falling from the surface.

For those organisms, like the Vampire Squid, who live in the oxygen minimum zone, special adaptations are needed to either make do with lesser amounts of oxygen or to extract oxygen from the water more efficiently. One strategy used by some classes of bacteria in the oxygen minimum zones is to use nitrate rather than oxygen, thus drawing down the concentrations of this important nutrient. The oxygen minimum zones thus play an important role in regulating the productivity and ecological community structure of the global ocean (Deutsch et al., 2007). For example, giant bacterial mats floating in the oxygen minimum zone off the west coast of South America may may play a key role in the region's extremely rich fisheries as bacterial mats the size of Uruguay have been found there. [1]

See also

References

a.   *Deutsch, C., J. L. Sarmiento, D. M. Sigman, N. Gruber, and J. P. Dunne, 2007: Spatial coupling of nitrogen inputs and losses in the ocean. Nature, 445(7124), 163-167.

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Dead zone (ecology) — This article is about the oceanic phenomenon. For other uses, see Dead Zone (disambiguation). Red circles show the location and size of many dead zones. Black dots show dead zones of unknown size. The size and number of marine dead zones areas… …   Wikipedia

  • Convection zone — An illustration of the structure of the Sun: 1. Core 2. Radiative zone 3. Convective zone 4. Photosphere 5. Chromosphere 6. Corona 7. Sunspot 8. Granules 9. Prominence …   Wikipedia

  • OMZ — Oxygen Minimum Zone (Medical » Physiology) Oxygen Minimum Zone (Governmental » NASA) Oxygen Minimum Zone (Governmental » Military) Oxygen Minimum Zone (Academic & Science » Chemistry) * Aeropuerto Caracas, Oscar Machado Zuloaga International… …   Abbreviations dictionary

  • Cold seep — Marine habitats Tube worms are among the dominant species in one of four cold seep community types in the Gulf of Mexico. Littoral zone …   Wikipedia

  • Anoxic event — As early as 1911, major oceanic currents were well mapped and understood, albeit without today s understanding of how they affect regional and global climatological conditions …   Wikipedia

  • Hypoxia — Infobox Disease Name = Hypoxia Caption = DiseasesDB = ICD10 = ICD9 = ICD9|799.02 ICDO = OMIM = MedlinePlus = eMedicineSubj = eMedicineTopic = eMedicine mult = MeshID = Hypoxia literally means a deficiency in oxygen. It can refer to:* Hypoxia… …   Wikipedia

  • Ausserirdischer Ozean — Der Ozean (Plural die Ozeane, von griechisch ὠκεανός („Ozean“, der die Erdscheibe umfließende Weltstrom, Personifikation als antiker Gott Okeanos)) bezeichnet die größten Meere der Erde. Synonym und als Ubertragung ins Deutschen auch Weltmeer[1] …   Deutsch Wikipedia

  • Ozeane — Der Ozean (Plural die Ozeane, von griechisch ὠκεανός („Ozean“, der die Erdscheibe umfließende Weltstrom, Personifikation als antiker Gott Okeanos)) bezeichnet die größten Meere der Erde. Synonym und als Ubertragung ins Deutschen auch Weltmeer[1] …   Deutsch Wikipedia

  • Weltmeere — Der Ozean (Plural die Ozeane, von griechisch ὠκεανός („Ozean“, der die Erdscheibe umfließende Weltstrom, Personifikation als antiker Gott Okeanos)) bezeichnet die größten Meere der Erde. Synonym und als Ubertragung ins Deutschen auch Weltmeer[1] …   Deutsch Wikipedia

  • Vampire Squid — Taxobox name = Vampire Squid regnum = Animalia phylum = Mollusca classis = Cephalopoda subclassis = Coleoidea superordo = Octopodiformes ordo = Vampyromorphida subordo = Vampyromorphina familia = Vampyroteuthidae genus = Vampyroteuthis genus… …   Wikipedia


We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.