Calibration of Sulfate Levels in the Archean Ocean
Kirsten S. Habicht,1
Michael Gade,1
Bo Thamdrup,1
Peter Berg,2
Donald E. Canfield1*
The size of the marine sulfate reservoir has grown
through Earth's history, reflecting the accumulation of oxygen into
the atmosphere. Sulfur isotope fractionation experiments on marine and
freshwater sulfate reducers, together with the isotope record, imply
that oceanic Archean sulfate concentrations were <200 µM, which is
less than one-hundredth of present marine sulfate levels and one-fifth
of what was previously thought. Such low sulfate concentrations were
maintained by volcanic outgassing of SO2 gas, and severely
suppressed sulfate reduction rates allowed for a carbon cycle dominated
by methanogenesis.
1 Danish Center for Earth System Science and
Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark.
2 Department of
Environmental Sciences, Clark Hall, University of Virginia, VA 22903, USA.
*
To whom correspondence should be addressed.
