Plate Nº 65 · recorded September 29, 2026
Earth & ClimateReported finding
Ancient Ocean Chemistry Kept Earth Breathing, Study Finds
Researchers show a phosphorus recycling loop in ancient oceans kept atmospheric oxygen high after the Great Oxidation Event, with implications for climate and the search for alien life.
By Nathan Brooks3 min read676 words
In brief
- Oxygen became permanent in Earth's atmosphere about 2.3 billion years ago during the Great Oxidation Event.
- Microbes used seawater sulfate to recycle phosphorus, fueling biological growth and burying organic carbon, which let oxygen accumulate in the atmosphere.
- A new technique that separates phosphorus by mineral type revealed how much of the nutrient was biologically available in ancient South African rocks.
Roughly 2.3 billion years ago, oxygen became a permanent feature of Earth's atmosphere during what scientists call the Great Oxidation Event. What happened next has puzzled researchers for decades: how did oxygen levels stay high enough, over millions of years, to support increasingly complex life? A new study published in Nature Communications offers an answer rooted in ocean chemistry.
The research, led in part by University of California, Riverside geologist Andrey Bekker, shows that changes in ancient seawater created a self-sustaining cycle that kept oxygen levels elevated after they first rose. The engine of that cycle was phosphorus, a chemical element that organisms need to grow.
A nutrient-driven oxygen loop
Phosphorus plays a central role in biology. "Living things cannot grow or function properly without phosphorus," Bekker explained. "Once more of it became available in the oceans, it allowed more organic carbon to be buried. A side effect of that process is that more oxygen continued to be released into the atmosphere."
The cycle worked like this. As oxygen spread through Earth's oceans, sulfate — a sulfur-oxygen compound — accumulated in seawater. Microbes used that sulfate to break down organic matter more efficiently, releasing phosphorus back into the water. That recycled phosphorus fueled new biological growth. More life meant more organic carbon buried in seafloor sediments, and burying organic carbon allows oxygen to accumulate in the atmosphere instead of being consumed by decay. Each turn of the loop reinforced the next.
Reading phosphorus in ancient rock
To test this idea, Bekker and his collaborators analyzed ancient rocks from South Africa. They used a new technique that separates phosphorus according to the types of minerals it is bound to. By dissolving each mineral type one at a time, the method reveals whether the phosphorus was biologically available or locked inside minerals that living systems could not use.
This matters because, until now, scientists could only measure the total amount of phosphorus preserved in rocks. That total said little about how much of the nutrient ancient life could actually access. "We can now separate the phosphorus that was available to organisms from phosphorus that was essentially locked away," Bekker said. "That gives us a much clearer picture of nutrient levels in ancient oceans than we had before."
Oxygen swings and the pace of complex life
The findings suggest that oxygen levels fluctuated far more dramatically in the aftermath of the Great Oxidation Event than scientists once believed. Those swings probably reshaped ocean chemistry over tens of millions of years and changed how nutrients cycled through the environment.
The results may also revise ideas about the evolution of early life. If oxygen remained abundant for extended stretches, Bekker notes, then some other environmental or biological factor — not a severe shortage of oxygen alone — may explain why oxygen-dependent, more complex organisms took so long to emerge.
The picture remains incomplete, and the researchers' conclusions rest on rock samples from one region interpreted through a relatively new analytical method. Still, the study offers a coherent mechanism connecting nutrient supply, biological productivity, and atmospheric oxygen across a critical chapter of Earth's history.
Relevance for today — and beyond
The work has implications closer to the present. Climate change is currently causing parts of the ocean to lose oxygen. If that trend continues, phosphorus could again become less available, which would reduce marine productivity and leave marine ecosystems less resilient.
The findings may also inform the search for life beyond Earth. Understanding how oxygen, nutrients, and living organisms evolved together on our planet could help scientists recognize similar conditions on ocean-bearing worlds elsewhere in the universe.
"Earth's history shows that oxygen, nutrients and life evolved together," Bekker said. "Understanding those connections gives us a more nuanced perspective on our own planet's future and what we might look for on other planets."
The study, by Lewis J. Alcott and colleagues, appears in Nature Communications under the title "A nutrient control on oxygenation dynamics during Earth's Great Oxidation Episode" (DOI: 10.1038/s41467-026-76597-y).
via Phys.org Space & Astronomy (Source)