Sea lettuce has been used in Japanese cuisine for thousands of years. Highly prized by dieticians, ulva is one of the best known food algae in Europe. In France, it has been harvested on the coasts of Brittany and Charente for more than ten years and is consumed as a marine spice for seasoning. It is integrated in the traditional cuisine from the gastronomic and dietetic point of view. Its ability to absorb nitrates means that it is used to decontaminate rivers by arranging strings of sea lettuce to filter the water. They are then harvested, replaced by new seaweed and buried.