Oxygen Minimum Zone (OMZ)

An oxygen-minimum zone is a mid-depth layer (roughly 100 to 1,000 m) of very low dissolved oxygen, formed where sinking organic matter is respired faster than sluggish circulation can resupply O2. The largest sit beneath the productive eastern tropical Pacific and Arabian Sea upwelling systems. Where oxygen approaches zero, denitrification and anammox remove fixed nitrogen, making OMZs important to the marine nitrogen cycle. They are expanding under warming.