The Earth's ancient oceans had much lower content of sulfate than previously thought, a new study has said.
The findings paint a new portrait of our planet's early biosphere and primitive marine life. Organisms require sulfur as a nutrient, and it plays a central role in regulating atmospheric chemistry and global climate.
Measuring these fingerprints in rocks older than 2.5 billion years, they discovered sulfate 80 times lower than previously thought.
Previous research has suggested that Archean sulfate levels were as low as 200 micromolar, concentrations at which sulfur would still have been abundantly available to early marine life. The new results indicate levels were likely less than 2.5 micromolar, thousands of times lower than today.
The study is published in Science.