Phytoplankton Produce a Huge Share of Earth Oxygen

We often link oxygen to forests, yet a major share comes from the sea. Phytoplankton in the sunlit upper ocean photosynthesize using sunlight. They are microscopic, but together they form a vast production line.\n\nAs phytoplankton turn carbon dioxide into organic matter, oxygen is released. Currents, nutrients, and light levels make this output rise and fall. The ocean, in a sense, breathes seasonally and regionally.\n\nIn detail, phytoplankton also sit at the base of the food web. Tiny animals eat them, bigger fish eat those animals, and the chain expands. Oxygen production and food production are powered by the same organisms.\n\nThat is why ocean health matters not only for fisheries but for the atmosphere. Pollution, warming, and acidification can disrupt this microscopic factory. When you take a breath, you are also inhaling the invisible work of the sea.