The Mississippi River, North America’s largest river system, is under threat. Air and water pollution, downstream flooding and coastal land loss are among the environmental pressures that are putting the health and future of the waterway — and the communities that depend on it — at risk.

What is the “Dead Zone?” And why is it growing in the Gulf of Mexico? Dr. Nancy Rabalais joins President William F. Tate IV to answer these questions; give a behind-the-scenes look at an oceanographer's life both on deck and below; and describe her journey to being elected to the most prestigious scientific society in the U.S., the National Academy of Sciences.