Guardian: The ocean has been our savior. Besides generating about two thirds of the oxygen we breathe, oceangoing phytoplankton — those floating microscopic plants that form the base of the aquatic food chain — absorb about a third of all the carbon dioxide we pump into the atmosphere. In this way, the oceans have managed to slow the buildup of heat-trapping greenhouse gases and stave off even more dramatic warming of the planet. But John Guinotte and colleagues are discovering that …