Marine scientists across the world are hunting for clues to one of the greatest environmental catastrophes facing our planet today: ocean acidification. For years we’ve known the ocean absorbs about a quarter of the carbon dioxide in Earth’s atmosphere. But as carbon emissions continue to rise, seawater chemistry is changing, and the ocean’s acidity is increasing. As a result, the skeletons and shells of marine creatures that form the foundation of the web of life are dissolving. Follow scientists who are seeking solutions and making breakthrough discoveries, including a unique coral garden in Papua New Guinea that offers a glimpse of what the seas could be like in a half-century.