Photosynthesis is the primary source of the Earth's oxygen. While various organisms contribute, the most significant contributors are plants and phytoplankton.
Terrestrial Plants: The Green Lungs
As stated in one source, "[T]he plants are one of the chief sources of oxygen."1 Through the process of photosynthesis, plants absorb carbon dioxide and release oxygen. Trees, grasses, and other land plants play a vital role in maintaining atmospheric oxygen levels.
Phytoplankton: The Ocean's Oxygen Factories
Oceanic plankton, including algae and certain bacteria, are incredibly important oxygen producers. Research indicates that "the majority of this production is from oceanic plankton — drifting plants, algae, and some bacteria that can photosynthesize."2 In fact, the ocean is estimated to produce at least 50% of the Earth's oxygen.3 These tiny organisms are often referred to as the "lungs of our planet".3
Other Contributors
It's important to note that while plants and phytoplankton are the dominant sources, other organisms, such as cyanobacteria,4,5 also contribute to oxygen production. However, their contribution is significantly less compared to plants and phytoplankton. It is a misconception that trees alone provide all the Earth's oxygen.6
The Big Picture: A Balanced Ecosystem
Terrestrial plants and marine phytoplankton work together to maintain a balanced level of atmospheric oxygen. Any significant disruption to these ecosystems could have far-reaching consequences for the planet’s oxygen supply.
1 Through plants - "The plants are one of the chief sources of oxygen."
2 How much oxygen comes from the ocean? - "The majority of this production is from oceanic plankton — drifting plants, algae, and some bacteria that can photosynthesize."
3 World Oceans Day | United Nations - "The ocean produces at least 50% of the planet's oxygen ... They are the lungs of our Planet..."
4 The strange history of atmospheric oxygen - "...cyanobacteria and other photosynthetic phytoplankton continue to be major sources of oxygen."
5 The Great Oxidation Event: How Cyanobacteria Changed Life - "...cyanobacteria...major component of the atmosphere."
6 How do trees give earth all its oxygen? | Science Questions with ... - "All of earths oxygen does not come from trees."
