Oxygen-Minimum Zone

Synonyms

Dead zone; Shadow zone

Acronyms

OMZ

Definition

The oxygen-minimum zone or OMZ is the zone in a body of water (lakes, oceans, etc.) in which the oxygen saturation is minimum and thus redox conditions are hypoxic (O₂ concentration <75 μmol/L) or anoxic (O₂ concentration <1 μmol/L).

Overview

In terrestrial oceans, the oxygen-minimum zone develops between 200 and 1,000 m below the sea level. The development of the OMZ in oceans is mainly related to the consumption of oxygen by aerobic bacteria degrading dead organisms descending through the water column from the above oxygenated ocean layer. At depths >1,000 m, the ocean is again oxygenated because the bottom currents bring cold, oxygen-rich, polar waters. On the continental platform, sediments in contact with the OMZ are also in anoxic conditions, allowing the preservation of buried organic matter. OMZ plays a key role in regulating the ecological community structure of the global ocean. In this zone important metabolic...