Calibration of Sulfate Levels in the Archean Ocean

• Published in: Science (American Association for the Advancement of Science) Vol. 298; no. 5602; pp. 2372 - 2374
• Main Authors: Habicht, Kirsten S., Gade, Michael, Thamdrup, Bo, Berg, Peter, Canfield, Donald E.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 20-12-2002; The American Association for the Advancement of Science
• Subjects: Anaerobiosis; Archaeoglobus fulgidus - growth & development; Archaeoglobus fulgidus - metabolism; Archean Eon; Archean era; Bacteria - growth & development; Bacteria - metabolism; Carbon; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fractionation; Fresh water; Fresh Water - chemistry; Fresh Water - microbiology; Geobiology; Geologic Sediments - chemistry; Geologic Sediments - microbiology; Iron - analysis; Isotopes; Marine; Marine geology; Methane - metabolism; Methane production; Oceans; Oceans and Seas; Oxidation-Reduction; Oxygen; Oxygen - analysis; Seawater - chemistry; Seawater - microbiology; Sediments; Sulfate minerals; Sulfates; Sulfates - analysis; Sulfates - metabolism; Sulfides; Sulfides - analysis; Sulfides - metabolism; Sulfur; Time; United States; World Oceans; sulfur dioxide; stable isotopes; models; degassing; ocean; chemical reduction; S-34/S-32; isotope fractionation; sulfates; Precambrian; Archean; volcanism
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1078265

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 $<200 \mu M$, 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 SO2gas, and severely suppressed sulfate reduction rates allowed for a carbon cycle dominated by methanogenesis.