JACKSONVILLE, FLA – Every second breath you take comes from the ocean. The oxygen you inhale is largely the work of phytoplankton—tiny plant-like organisms floating at the surface of the sea. Through photosynthesis, they produce nearly half the oxygen on Earth.
But this life-sustaining system depends on a scarce ingredient: iron. Phytoplankton need it to fuel photosynthesis, and without it, oxygen production falters.
A new Rutgers University study, published in the Proceedings of the National Academy of Sciences, shows just how critical iron is to the ocean’s invisible oxygen factory.
“Every other breath you take includes oxygen from the ocean, released from phytoplankton,” said Paul G. Falkowski, a Rutgers–New Brunswick researcher and co-author. “Our research shows that iron is a limiting factor in phytoplankton’s ability to make oxygen in vast regions of the ocean.”
Why Iron Counts
Iron reaches the sea as dust blown off deserts or carried in glacial melt. When it’s scarce, phytoplankton’s photosynthesis slows, limiting their growth and their ability to pull carbon dioxide from the atmosphere.
Humans won’t run out of oxygen, but the ocean food chain feels the pinch.
“Phytoplankton feed krill, which feed penguins, seals, walruses, and whales,” Falkowski said. “When iron levels drop, there’s less food—and fewer of these majestic creatures.”
At Sea With Phytoplankton
To test this, Rutgers graduate researcher Heshani Pupulewatte spent 37 days aboard a British research vessel in the South Atlantic and Southern Ocean. Using custom-built sensors, she measured how phytoplankton respond to iron stress in real time.
Her work revealed that up to 25% of light-harvesting proteins “uncouple” when iron is low, wasting sunlight instead of turning it into energy. Once iron was added, the organisms bounced back almost immediately.
The Bigger Picture
These findings reveal how something as small as dust from deserts or melting ice shapes the oxygen we breathe and the carbon balance of our planet. As climate change alters wind and ocean circulation, iron supplies to the sea could shift, rippling through ecosystems.