Gulf of Mexico Hypoxia Zone
Source: U.S. Geological Survey
Map Description:
The hypoxic zone in the northern Gulf of Mexico refers to an area along the Louisiana-Texas coast in which water near the bottom of the Gulf contains less than 2 parts per million of dissolved oxygen. Hypoxia can cause fish to leave the area and can cause stress or death to bottom dwelling organisms that can�t move out of the hypoxic zone. Hypoxia is caused primarily by excess nitrogen delivered from the Mississippi River in combination with seasonal stratification of Gulf waters. Nitrogen promotes algal and attendant zooplankton growth. The associated organic matter sinks to the bottom where it decomposes, consuming available oxygen. Stratification of fresh and saline waters prevents oxygen replenishment by mixing of oxygen-rich surface water with oxygen-depleted bottom water. The National Oceanic and Atmospheric Administration (NOAA) provides a Gulf of Mexico Hypoxia Watch System as a public service.

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