New Orleans is a city defined by Mardi Gras, jazz, and oysters – lots of oysters. For more than 150 years, Louisiana was the nation’s largest source of the shellfish. Thanks to a perfect combination of brackish and warm water, each day thousands of tons of oysters were harvested and imported around the country. By 2010, the state supplied nearly 42 percent of the nation's oysters. But then the Deepwater Horizon blowout happened.