Sulfate (SO42-) is the second-most abundant anion after chloride in the modern ocean. It serves as an easily accessible energy source for sulfate-reducing prokaryotes (SRPs), which are commonly found in organic-rich sediments and play an important role in the decomposition of organic matter. Were these microbes major players in ecosystems during the Archean (before 2.5 billion years ago), when molecular oxygen was virtually absent from both the atmosphere and oceans? Whether this was the case depends on how much sulfate there was in the Archean ocean. Three articles in this issue (1–3) use precise measurements of stable sulfur isotope ratios to investigate how much sulfate there was in the Archean ocean and where that sulfate originated. |
