How did photosynthetic cyanobacteria contribute to the Great Oxidation Event?

The Great Oxidation Event, which began approximately 2.4 billion years ago, was primarily driven by the metabolic activity of photosynthetic cyanobacteria. These organisms evolved the ability to perform oxygenic photosynthesis, a process that uses light energy to convert water and carbon dioxide into carbohydrates, releasing free oxygen as a byproduct.123

For a significant period, this oxygen did not accumulate in the atmosphere because it was consumed by chemical sinks, most notably the vast quantities of dissolved ferrous iron in the oceans. Cyanobacterial metabolism facilitated the conversion of this soluble iron into insoluble ferric iron, which precipitated out of the water to form extensive iron formations.345

Once these primary oxygen sinks—such as the oceanic iron—were largely depleted, the oxygen produced by cyanobacteria began to accumulate in the atmosphere. This rise in atmospheric oxygen levels fundamentally transformed Earth’s environment, enabling the development of aerobic metabolism and paving the way for the evolution of complex, multicellular life.35421