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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 ...
The boundary between the Ordovician and Silurian periods is marked by repetitive periods of anoxia, interspersed with normal, oxic conditions. In addition, anoxic periods are found during the Silurian. These anoxic periods occurred at a time of low global temperatures (although CO 2 levels were high), in the midst of a glaciation. [29]
Dysoxic water can be interpreted as having a moderate amount of oxygen, or oxygen varying through time between oxic and anoxic, oxic and dysoxic, or dysoxic and anoxic conditions. If the benthic oxygen was variable, the rates of change in the oxygen will affect organic carbon preservation, benthic fossil abundance and diversity, and oxygen ...
Euxinia or euxinic conditions occur when water is both anoxic and sulfidic.This means that there is no oxygen (O 2) and a raised level of free hydrogen sulfide (H 2 S). Euxinic bodies of water are frequently strongly stratified; have an oxic, highly productive, thin surface layer; and have anoxic, sulfidic bottom water.
Hypoxia (hypo: "below", oxia: "oxygenated") refers to low oxygen conditions. Hypoxia is problematic for air-breathing organisms, yet it is essential for many anaerobic organisms. Hypoxia applies to many situations, but usually refers to the atmosphere and natural waters.
Anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: Anoxic waters, sea water, fresh water or groundwater that are depleted of dissolved oxygen; Anoxic event, when the Earth's oceans become completely depleted of oxygen below the surface levels
In OMZs oxygen concentration drops to levels <10 nM at the base of the oxycline and can remain anoxic for over 700 m depth. [7] This lack of oxygen can be reinforced or increased due to physical processes changing oxygen supply such as eddy-driven advection, [7] sluggish ventilation, [8] increases in ocean stratification, and increases in ocean temperature which reduces oxygen solubility.
In dimictic, eutrophic lakes, the hypolimnion is often anoxic throughout a majority of the stratified period. [6] However, hypolimnetic oxygen concentrations are replenished in the fall and early winter in many temperate lakes, as lake turnover allows mixing of oxic surface waters and anoxic bottom waters. [7]