October 1, 2025 — Half the oxygen in your next breath did not come from trees on land. Scientists estimate that phytoplankton in the ocean make about half of the oxygen in the air in Earth’s atmosphere.
These microscopic drifters depend on nutrients that large whales move to the sunlit surface when they release nutrient rich waste.
Field research shows that marine mammals enhance primary productivity by concentrating nitrogen near the surface through flocculent fecal plumes.
Phytoplankton and oxygen
After decades of field work, Robert Kenney, an emeritus marine research scientist at the University of Rhode Island (URI), has traced how whales, prey, and currents shape each season. His perspective helps connect nutrients, food webs, and survival across years.
Phytoplankton are tiny photosynthetic organisms that turn sunlight and carbon dioxide into sugar and oxygen. Zooplankton are small animals that graze on them and feed fish, seabirds, and whales.
When nutrients are scarce near the surface, phytoplankton growth slows and the whole food web tightens. When nutrients pulse upward, growth accelerates and energy ripples through the system.
Whales often feed at depth and then return to the surface to rest, breathe, and digest. When they defecate near the surface, their waste carries nitrogen and iron that phytoplankton can use right away.
That burst of nutrients supports fast growth, which boosts food for krill and fish in the upper ocean. Many large whales filter this prey using baleen, flexible plates in their mouths that act like a sieve.
The loop continues when predators eat that prey and release nutrients again in shallow water. Over time, this recycling keeps productivity higher than it would be without whales.