Book excerpt: All life — whether on land or in the sea — depends on the oceans for two things: • Oxygen. Most of Earth’s oxygen is produced by phytoplankton in the sea. These humble, one-celled organisms, rather than the spectacular rain forests, are the true lungs of the planet. • Climate control. Our climate is regulated by the ocean’s currents, winds, and water-cycle activity. Sea Sick is the first book to examine the current state of the world’s oceans — the great unexamined ecological crisis of the planet — and the fact that we are altering everything about them; temperature, salinity, acidity, ice cover, volume, circulation, and, of course, the life within them. Alanna Mitchell joins the crews of leading scientists in nine of the global ocean’s hotspots to see firsthand what is really happening around the world. Whether it’s the impact of coral reef bleaching, the puzzle of the oxygen-less dead zones such as the one in the Gulf of Mexico, or the shocking implications of the changing Ph balance of the sea, Mitchell explains the science behind the story to create an engaging, accessible yet authoritative account.