What are the major source of oxygen in the earth’s atmosphere? As this question came in my mind today, I started searching it in google and found that the major source of oxygen is marin plants that generate about 70% of the oxygen in the atmosphere. 28% oxygen comes from rainforests and the rest of 2% from other sources. Study shows that the ocean contains millions of phytoplankton, kelp, and algai plankton that produce countless tons of oxygen byproduct of photosynthesis. I had read about photosynthesis either in 9th or 10th standard. Photosythesis is a process which with the help of sunlight energy converts carbon dioxide and water into sugars and produce oxygen. [The image is sourced from oceanservice.noaa.gov] #Science