In today’s Academic Minute, Dr. Timothy Lyons of the University of California Riverside explains the complex history of the Earth’s oxygen-rich oceans.
Timothy Lyons is a professor of biogeochemistry at the University of California, Riverside, where his current research explores the evolving ocean and atmosphere and their cause-and-effect relationships with the origin and evolution of life. His work has appeared in numerous academic journals and he holds a Ph.D. from Yale University.
Dr. Timothy Lyons – Ocean Oxygen
The oldest signs of animal life appear in the geologic record around 600 million years ago. For the four billion years prior, our planet experienced dramatic changes that paved the way for this milestone—and our own existence. Yet most of us take these changes for granted. One such transformation was the first rise of oxygen about two-and-a-half billion years ago, perhaps the single most important environmental change in history. Before then, Earth’s atmosphere and oceans were virtually devoid of this life-giving gas, which now makes up 20% of the air we breathe.
My research group is exploring the evolving compositions of the early atmosphere and oceans. Our favorite questions center on the cause-and-effect relationships between life and its environment across the critical middle chapters of Earth history—the roughly two billion years between the first production of oxygen via photosynthesis and the first appearance of animals.
Our work shows us that the initial rise of oxygen may have occurred in fits and starts rather than a single step—and that once permanently present in the atmosphere, oxygen likely rose to very high levels and then plummeted. One-and-a-half billion years of oxygen-free conditions in the deep ocean resulted and set a challenging course for the simple microscopic inhabitants. Then, about 600 million years ago, thanks perhaps to a flush of nutrients to the ocean in the wake of history’s greatest ice age, life and photosynthesis flourished, oxygen took another step up—and animals first hit the scene.
Darwin was long troubled in his efforts to explain this initial explosion of animal life. He would be pleased to know that ancient rocks in fact reveal the history of life’s initial ups and down that set the stage—in so many ways—for the later evolution of animals. The story of the ancient ocean is the story of our origins, and it may just tell us a thing or two about the challenges in our future.