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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 exaerobic zone is found at the boundary of anoxic and hypoxic zones. Hypoxia can occur throughout the water column and also at high altitudes as well as near sediments on the bottom. It usually extends throughout 20–50% of the water column, but depends on the water depth and location of pycnoclines (rapid changes in water density with depth).
An anoxic event describes a period wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O 2), creating toxic, euxinic (anoxic and sulfidic) waters. [1] Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past.
Anoxic event – Historic oxygen depletion events in Earth's oceans Anoxic waters – Areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen Cultural eutrophication – Phenomenon where nutrients accumulate in water bodies Pages displaying short descriptions of redirect targets
Anoxic event – Historic oxygen depletion events in Earth's oceans; Anoxic waters – Areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen; Ocean acidification – Decrease of pH levels in the ocean; Seaweed – Macroscopic marine algae
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
Oceanic Anoxic Event II is believed to have caused the longest duration and most potent water column stratification in Western Interior Seaway history. [8] Although there has been much research devoted to Western Interior Seaway strata, the impact of Oceanic Anoxic Event II on the oxygen content of the benthic zone is still contested.
[74] [75] [76] Depletion of manganese in sediments corresponding to OAE2 provides additional strong evidence of severe bottom water oxygen depletion. [54] An increase in the abundance of the planktonic foraminifer Heterohelix provides further evidence still of anoxia.