Contrary to popular belief, most of the oxygen on earth does not come from trees. So, where does oxygen come from?

In fact, according to scientists, the ocean and phytoplankton produce between 50% and 80% of the oxygen on our planet.

Why do we mistakenly think that trees produce most of our oxygen?

Well, that’s a shortcut we make, that’s what our parents tell us, that’s what we learn at school. But, according to a 2010 study by science.org, tropical forests are responsible for about 34% of the earth’s photosynthesis.

This does not change the fact that trees are very important, they make oxygen from the carbon dioxide in the air (CO2). They are true natural carbon dioxide (CO2) recycling machines. They simply produce less oxygen than we think.

So where is all the oxygen produced?

We tend to forget this, but phytoplankton and the oceans produce more than 50% of the oxygen on our planet. Phytoplankton are the largest producers of oxygen on earth. Like land plants, phytoplankton make oxygen through the mechanism of photosynthesis.

What are phytoplankton?

Phytoplankton, or plant plankton, are micro-organisms that are invisible to the naked eye. These tiny one-celled plants just float in the ocean surface, and go with the flow and they drift with the currents.

They grow through photosynthesis, meaning they convert CO2 using the sun energy, and release oxygen. They also need nutrients from the bottom of the ocean itself like iron, nitrogen or phosphate. Not only do they provide oxygen for all of us on earth, but phytoplankton are also at the bottom of the food chain in the ocean. Small fish eat them and are in turn eaten by bigger fishes.. Surprising as it may seem, it is not huge trees but these tiny plant organisms that play a major role in renewing the oxygen in the air we breathe.

Unfortunately, phytoplankton are in danger because of global warming (if you want to read more about global warming, we invite you to read our article “Climate change is accelerating“. Indeed, they prefer cold waters and as the ocean temperature increases, the population of phytoplankton decreases. This will have a big impact on marine biodiversity and on the land in general as phytoplankton is also part of the food chain.

How does phytoplankton photosynthesis work?

To put it simply, thanks to its chlorophyll, phytoplankton captures sunlight which it uses as a source of energy to produce glucose. To create this sugar, it needs carbon and hydrogen, two elements that it finds in the carbon dioxide (CO2) and water (H2O) naturally present in its environment. It then releases what it does not need, namely O2, oxygen.

If you want to read more about phytoplankton, please read our article “phytoplankton are the biggest producers of oxygen on earth“.

Sources:  National Geographic, Science.org.