Satellite image of the northern Gulf of Mexico/Mississippi Delta showing hypoxic coastal water (light blue). This color change is due to excessive nutrients being washed into the sea. Source: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC, January 2003.
When production increases in an ecosystem, organic matter, such as algal cells and fecal pellets, increases. This situation can lead to hypoxia when decaying bottom organic matter depletes oxygen and water stratification blocks oxygen replenishment. Upwelling oxygen-rich water or destruction of the stratification can alleviate this problem. Diagram courtesy of the U.S. Environmental Protection Agency.