A new USGS study shows that the Gulf of Mexico’s dead zone is caused mainly from corn and soy fertilizers and animal wastes running off of the seven states abutting the Mississippi, and also Indiana and Ohio along the Ohio River, which drains into the Mississippi. Ocean dead zones are caused by extremely low oxygen levels in the water – a condition known as hypoxia. Hypoxic conditions develop where there is an excess of agricultural run-off, because of the high levels of nitrogen and phosphorous in fertilizer and manure.
