What produces 70% of the oxygen on Earth?

About 70% of the oxygen on Earth is produced by marine plants and microorganisms, especially phytoplankton. These are microscopic organisms that live in oceans, seas, and even freshwater. Through photosynthesis, they convert sunlight, water, and carbon dioxide into energy releasing oxygen as a natural byproduct.

Phytoplankton may be invisible to the naked eye, but collectively, they play a bigger role in oxygen generation than all the world’s forests combined. They form the foundation of the marine food web, supporting everything from small fish to whales, while also regulating the planet’s carbon and oxygen balance.

Land-based vegetation, such as tropical rainforests, grasslands, and other green plants, contribute the remaining 30% of Earth’s oxygen. However, the ocean-based sources dominate due to their vast coverage nearly 70% of Earth’s surface is ocean.

Preserving these tiny oxygen producers is crucial. Activities like overfishing, oil spills, and plastic pollution harm marine life and disrupt oxygen cycles. Supporting ocean conservation helps ensure that phytoplankton continue producing oxygen for all living beings. In short, our planet’s main oxygen source lies beneath the waves—not just in forests, but in the life-filled blue waters of Earth’s oceans.