Gulfcoast - Blog Posts

Every year a dead zone forms in the Gulf of Mexico. This year’s dead zone is the largest on record. 

From the New Orleans Times-Picayune:

“Nitrogen and phosphorus pollution enters the Mississippi [River] throughout its watershed, which includes runoff from the Midwest cropland and factory livestock and chicken farms, and pollutants from sewer systems and septic tanks in other locations...The lighter freshwater containing the nutrients creates a layered effect when it reaches the Gulf and the nutrients trigger blooms of phytoplankton - microscopic marine algae - in the spring and summer. The fresher, warmer water in the upper layer is separated from the saltier, colder water in the lower layer, resulting in a barrier to the normal diffusion of oxygen from the surface to the bottom... When the algae dies and sinks to the bottom, it decomposes, using up oxygen in the deeper heavy saltwater and creating dead zone conditions. Those conditions don't change until wind or weather, especially tropical storms or hurricanes, mix the freshwater at the surface into the saltier water.”

A monitoring cruise measured a dead zone of 8,776 square miles, “4 1/2 times the size of the of the goal of about 1,950 square miles set by the federal-state Mississippi River Nutrient/Hypoxia Task Force.” The result are marine life, such as crabs and crustaceans, that die due to oxygen deprivation.