A Thiosulfate Shunt in the Sulfur Cycle of Marine Sediments

• Published in: Science (American Association for the Advancement of Science) Vol. 249; no. 4965; pp. 152 - 154
• Main Author: Jorgensen, Bo Barker
• Format: Journal Article
• Language: English
• Published: United States American Society for the Advancement of Science 13.07.1990; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: 540311 - Environment, Aquatic- Basic Studies- Radiometric Techniques- (1990-); 540320 - Environment, Aquatic- Chemicals Monitoring & Transport- (1990-); ANOXIA; Atoms; BACTERIA; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BIOGEOCHEMISTRY; CHALCOGENIDES; CHEMICAL REACTIONS; CHEMISTRY; Composition; DAYS LIVING RADIOISOTOPES; Electrons; ENVIRONMENTAL SCIENCES; EVEN-ODD NUCLEI; FRESH WATER; GEOCHEMISTRY; HYDROGEN COMPOUNDS; ISOTOPE APPLICATIONS; ISOTOPES; LIGHT NUCLEI; Marine; Marine sediments; MICROORGANISMS; NUCLEI; Oxidation; OXYGEN COMPOUNDS; RADIOISOTOPES; REDOX REACTIONS; SEAS; SEDIMENTS; Slurries; SULFATE-REDUCING BACTERIA; SULFATES; SULFIDES; SULFUR 35; SULFUR COMPOUNDS; SULFUR CYCLE; SULFUR ISOTOPES; SURFACE WATERS; THIOSULFATES; TRACER TECHNIQUES; WATER; WATER CHEMISTRY
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.249.4965.152

The oxidation of sulfide, generated by bacterial sulfate reduction, is a key process in the biogeochemistry of marine sediments, yet the pathways and oxidants are poorly known. By the use of $^{35}$S-tracer studies of the S cycle in marine and freshwater sediments, a novel shunt function of thiosulfate (S$_2$O$_3^{2-}$) was identified. The S$_2$O$_3^{2-}$ constituted 68 to 78 percent of the immediate HS$^-$-oxidation products and was concurrently (i) reduced back to HS$^-$, (ii) oxidized to SO$_4^{2-}$, and (iii) disproportionated to HS$^-$ + SO$_4^{2-}$. The small thiosulfate pool is thus involved in a dynamic HS$^-$-S$_2$O$_3^{2-}$ cycle in anoxic sediments. The disproportionation of thiosulfate may help account for the large difference in isotopic composition ($^{34}$S/$^{32}$S) of sulfate and sulfides in sediments and sedimentary rocks.