Sulfur is a crucial component of biomass and an important source of energy for microbial metabolisms. It also plays a central role in regulating atmospheric chemistry and global climate over geologic timescales.
|Research vessel on Lake Matano, Indonesia. |
PHOTO by Sean Crowe, University of British Columbia.
“These results suggest that sulfate levels in the Archean could have been thousands of times lower than today, which would have had important consequences for the cycling of sulfur in the oceans and atmosphere, and for the evolution of early microbial ecosystems”, says Dr Aubrey Zerkle, a Lecturer in the Department of Earth & Environmental Sciences and collaborator on the study. Two additional papers published in the same issue of Science used similar techniques to examine sulfur isotope signatures of in ancient sediments from ~2.5 billion years ago. These studies suggest dynamic spatial and temporal variations of seawater sulfate during that time, supporting a low-sulfate scenario. However, both indicate that microbial ecosystems based on sulfur cycling still thrived, despite the lack of sulfate.