What causes a dead zone or hypoxia to occur?
ROB MAGNIEN: Hypoxic zones can occur naturally, but the ones we are most concerned about are those created or enhanced by human activity. There are many physical, chemical, and biological factors that conspire to create dead zones, but nutrient pollution is the primary cause of those created by humans. Excess nutrients that run off land or are piped as wastewater into our rivers and coasts can stimulate an overgrowth of algae, which then sinks and decomposes in the water. The decomposition process consumes oxygen and depletes the supply available to healthy marine life. HOST: Where do dead zones occur in the U.S.? ROB MAGNIEN: Kate, dead zones occur in many areas of the country, particularly along the East Coast, the Gulf of Mexico, and the Great Lakes, but there is no part of the country, or the world for that matter, that is immune. The second largest dead zone in the world is located right here in the U.S. in the northern Gulf of Mexico and the ones in the Chesapeake Bay and Lake Er
