Scientists estimate that oceanic photosynthesis contributes about half of global oxygen production, largely through phytoplankton. That does not mean every second breath contains brand-new ocean oxygen or that net atmospheric oxygen rises by that amount each year.
Three things to know
- Global production
- ~50%
- A broad estimate for gross oxygen production by ocean photosynthesizers.
- Main producers
- Phytoplankton
- Microscopic algae and cyanobacteria photosynthesize in sunlit water.
- Carbon role
- Biological pump
- Growth and sinking help move carbon into the ocean interior.
Tiny organisms doing a huge job
Phytoplankton use sunlight, carbon dioxide, water and nutrients to build organic matter and release oxygen. They form the base of most open-ocean food webs, supporting zooplankton, fish and ultimately much larger predators.
Making oxygen is not the same as storing it
Respiration and decomposition consume much of the oxygen that photosynthesis produces. Long-term accumulation depends on a small imbalance between production and consumption, including burial of organic carbon. The familiar half-of-oxygen statement describes gross production, not a simple annual deposit.
Blooms depend on more than sunlight
Nutrients, mixing, temperature and grazing determine where phytoplankton grow. Satellites map surface chlorophyll and color, while ships measure species and chemistry. A greener patch is productive, but it can also signal a harmful bloom depending on the organisms and conditions.
What people usually ask
Can we see phytoplankton from space?
Large surface blooms change ocean color and can be detected by satellite sensors, though samples are needed to identify species.
Would losing plankton remove half our oxygen immediately?
No. The atmosphere holds a huge oxygen reservoir, but plankton loss would severely disrupt food webs and carbon cycling.
Here’s where the answer came from
Open the original government science or research-institution source behind this page.