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Ancient Stromatolite Reefs
Photo: Ancient stromatolite reefs still flourish in high-saline Shark Bay
WALLPAPER
Microbe-rich stromatolite reefs, like this one in Shark Bay, Australia, were among the first sources of oxygen on Earth. They flourished throughout the planet's shallow waters 3.5 billion years ago, but are extremely rare today.
Photograph by O. Louis Mazzatenta

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