Areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen
Anoxic waters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen. The US Geological Survey defines anoxic groundwater as those with dissolved oxygen concentration of less than 0.5 milligrams per litre.[1] Anoxic waters can be contrasted with hypoxic waters, which are low (but not lacking) in dissolved oxygen. 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,[2] 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,[3] and have occurred throughout geological history. The Permian–Triassic extinction event, a mass extinction of species from the world's oceans, may have resulted from widespread anoxic conditions combined with ocean acidification driven by a massive release of carbon dioxide into Earth's atmosphere.[4] Many lakes have a permanent or temporary anoxic layer created by respiration depleting oxygen at depth and thermal stratification preventing its resupply.[5]
Anoxic basins exist in the Baltic Sea,[6] the Black Sea, the Cariaco Trench, various fjord valleys, and elsewhere.[7] Eutrophication has likely increased the extent of anoxic zones in areas including the Baltic Sea, the Gulf of Mexico,[8] and Hood Canal in Washington State.[9]
^"Volatile Organic Compounds in the Nation's Ground Water and Drinking-Water Supply Wells: Supporting Information: Glossary". US Geological Survey. Retrieved 3 December 2013.
^Bjork, Mats; Short, Fred; McLeod, Elizabeth; Beer, Sven (2008). Managing Sea-grasses for Resilience to Climate Change. Volume 3 of IUCN Resilience Science Group Working Papers. Gland, Switzerland: International Union for Conservation of Nature (IUCN). p. 24. ISBN 978-2-8317-1089-1.
^Richards, 1965; Sarmiento 1988-B
^McElwain, Jennifer C.; Wade-Murphy, Jessica; Hesselbo, Stephen P. (2005). "Changes in carbon dioxide during an oceanic anoxic event linked to intrusion into Gondwana coals". Nature. 435 (7041): 479–482. Bibcode:2005Natur.435..479M. doi:10.1038/nature03618. ISSN 0028-0836. PMID 15917805. S2CID 4339259.
^Wetzel, Robert G. (2001). Limnology : lake and river ecosystems (3rd ed.). San Diego: Academic Press. ISBN 0-12-744760-1. OCLC 46393244.
^Jerbo, 1972;Hallberg, 1974
^Skei, J. M. (1983). "Permanently Anoxic Marine Basins: Exchange of Substances across Boundaries". Ecological Bulletins (35): 419–429. ISSN 0346-6868. JSTOR 20112877.
^"Streamflow and Nutrient Delivery to the Gulf of Mexico for October 2009 to May 2010 (Preliminary)". Archived from the original on 2012-11-29. Retrieved 2011-02-09.
^"Archived copy" (PDF). Archived from the original (PDF) on 2011-09-27. Retrieved 2013-03-05.{{cite web}}: CS1 maint: archived copy as title (link)
Anoxicwaters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen. The US Geological Survey defines anoxic groundwater...
waters. Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past. Anoxic events...
used in various contexts: Anoxicwaters, sea water, fresh water or groundwater that are depleted of dissolved oxygen Anoxic event, when the Earth's oceans...
Subsurface productivity is limited by nutrient availability, as the anoxic bottom waters act as a sink for reduced nitrate, in the form of ammonia. The benthic...
date to Antiquity. In 1976, Willard Bascom suggested that the deep, anoxicwaters of the Black Sea might have preserved ships from antiquity because typical...
Euxinia or euxinic conditions occur when water is both anoxic and sulfidic. This means that there is no oxygen (O2) and a raised level of free hydrogen...
Mountaintop removal mining • Slurry impoundments Water (depletion) — Anoxicwaters • Aral Sea • California Water Wars • Dead Sea • Lake Chad • Water scarcity...
needs of the grass roots and also helps to aerate the surrounding mud. Anoxicwaters Firedamp, produced naturally in coal mines Hydric soil Landfill gas...
darkness that lies beneath the photic zone and includes most of the ocean waters. In the photic zone, the photosynthesis rate exceeds the respiration rate...
proliferation of anoxicwaters notably preceded the appearance of other geochemical indicators of the expansion of anoxia. A more direct proxy for anoxic conditions...
School of Oceanography. In 1976, Willard Bascom suggested that the deep, anoxicwaters of the Black Sea might have preserved ships from antiquity because typical...
(~500 gCm−2yr−1), causes the basin to be permanently anoxic, below ~250 m. This naturally occurring anoxic basin allows for sediments to be deposited without...
Eastern Gotland Basin is the Gotland Deep (249 metres deep) which is an anoxic basin. The Western Gotland Basin contains Landsort Deep, which is the deepest...
decades or seasonally for a shorter periods. Flooding results in oxygen-free anoxic processes prevailing, especially in the soils. The primary factor that distinguishes...
deserts", which are mostly at the centers of gyres, but also hypoxic or anoxicwaters such as dead zones. Deserts usually have a large diurnal and seasonal...
subsequently reducing the likelihood or extent of harmful algal blooms or anoxic conditions. Filter feeding activity is considered beneficial to water quality...
per liter, waters are considered hypoxic. When dissolved oxygen concentrations are approximately 0 milligrams per liter, conditions are anoxic. Both hypoxic...
amongst the mini-basins in this area, in containing a large brine pool of anoxic salt brine. The pool is approximately 123 km2 (47 sq mi) in area and up...
create water pollution. This pollutant load can reach various receiving waters such as streams, rivers, lakes, estuaries and oceans with resultant water...
When rising river waters first contact previously dry soil, the waters become oxygen-depleted, rendering the water environs anoxic. Many natural fish...
9.7m and was left about 150 million years ago when the crab died in an anoxic lagoon. The footprints left enough evidence for researchers to determine...
Three Western Interior Seaway anoxic events occurred during the Cretaceous in the shallow inland seaway that divided North America in two island continents...
date to Antiquity. In 1976, Willard Bascom suggested that the deep, anoxicwaters of the Black Sea might have preserved ships from antiquity because typical...
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