Sulfate on the early Earth – how low was low?

Findings recently published in Science (“Sulfate was a trace constituent of Archean seawater”, DOI: 10.1126/science.1258966) suggest that sulfate – a key biological nutrient – could have been incredibly scarce in the Earth’s ancient oceans.

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.

Researchers led by Dr Sean Crowe, a lead author of the study in the Departments of Microbiology and Immunology, and Earth, Ocean and Atmospheric Sciences at the University of British Columbia, collected samples from Lake Matano, Indonesia—a sulfate-poor modern analogue for the Earth’s Archean oceans – to examine the isotope effects associated with sulfur metabolisms under early Earth conditions. The team used state-of-the-art mass spectrometric approaches developed at California Institute of Technology to demonstrate that microorganisms in this lake fractionate sulfur isotopes at concentrations orders of magnitude lower than previously recognized.

“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.

"Can a Scientist Trust the New Testament?"

The Professor N T Wright, DD, of the School of Divinity, will be delivering the James Gregory Lecture on Science and Christianity at the Physics Lecture Theatre (School of Physics, North Haugh) on Monday, 17 February 2014, from 17:15 - 19:00.
  
Professor Wright will be discussing the difference between scientific, historical and theological knowledge, and the importance of getting all three in proper relation.  He will also address particular claims of the New Testament, the challenges they posed in their own day and continue to pose today, and whether the New Testament should be considered trustworthy today.

The Lecture is open to the public.  For more information please contact Dr Andrew Torrance (School of Divinity).

Celebrating Scholarship: Professorial Colloquia in Arts and Science

Arts and Humanities Colloquium:

Wednesday, 20th April, 2pm-5pm

Speakers:  Professors John Burnside, Kristin de Troyer, Katherine Hawley

Parliament Hall, South Street, St Andrews

Sciences Colloquium:

Wednesday, 11th May, 2pm-5pm

Speakers:  Professors Ian Gent, Martin Ryan, Chris Hawkesworth

Parliament Hall, South Street, St Andrews

These two events, one focusing on the Arts and Humanities and the other on the Sciences, are aimed at showcasing the very best scholarship that St Andrews has to offer.  They are multidisciplinary events that are designed to encourage discussion and debate across academic disciplines.  Both lectures are open to the public and all are welcome.