How do fertilizers cause oxygen depletion in the Gulf of Mexico?

Fertilizers contribute to oxygen depletion in the Gulf of Mexico through a process known as cultural eutrophication.12

When agricultural runoff containing nitrogen and phosphorus enters the Mississippi River and flows into the gulf, these nutrients act as a fertilizer for marine phytoplankton. This influx triggers excessive population growth, or algal blooms, on the water's surface. As these massive quantities of phytoplankton die, they sink to the bottom and decompose. The decomposition process consumes the dissolved oxygen in the water, leading to hypoxia—a condition where oxygen levels drop so low that most aquatic life, such as shrimp, crabs, and fish, cannot survive. This creates a "dead zone" that can span thousands of square miles, causing significant harm to marine ecosystems and local fisheries.3214

Addressing this environmental degradation is a moral imperative, as it requires improved agricultural and industrial practices to protect the health of our oceans and the diverse life they support.13