What caused the dead zone in the Gulf of Mexico?
Robert Spencer
Updated on May 10, 2026
The annual Gulf of Mexico dead zone is primarily caused by excess
nutrient pollution
Nutrient pollution is the process where too many nutrients, mainly nitrogen and phosphorus, are added to bodies of water and can act like fertilizer, causing excessive growth of algae. Nutrients can run off of land in urban areas where lawn and garden fertilizers are used.
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How did the Gulf of Mexico dead zone form?
What Causes the Dead Zone? Heavy rains and melting snows washed massive amounts of nutrients—particularly nitrogen and phosphorus—from lawns, sewage treatment plants, farm land and other sources along the Mississippi River into the Gulf of Mexico.What contaminant causes the Gulf of Mexico dead zone?
Nitrogen and phosphorus pollution in runoff and discharges from agricultural and urban areas are the major contributors to the annual summer hypoxic zone in the Gulf of Mexico.What is the reason a dead zone in Gulf Mexico became smaller?
2020 Gulf of Mexico Hypoxic Zone SizeThe earlier forecast for the dead zone was higher at 6,700 square miles. A major factor for the smaller measured size was due to extensive mixing caused by hurricane Hanna, which passed through the Gulf right ahead of the survey cruise.