The oxygen you breathe depends on a tiny ocean ingredient

Microscopic ocean algae produce a huge share of Earth’s oxygen—but they need iron to do it. New field research shows that when iron is scarce, phytoplankton waste energy and photosynthesis falters. Climate-driven changes may reduce iron delivery to the oceans, weakening the base of marine food chains. Over time, this could mean fewer krill and fewer whales, seals, and penguins.