Biogeochemical sulfur transformations in modern and ancient aquatic systems: Multiple isotope approach

Alexey Kamyshny, Geological & Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel

Recent studies of the four stable isotopes of sulfur (³²S, ³³S, ³⁴S, and ³⁶S) have revealed features of the sulfur isotope system, which provide the opportunity to extract information from the analysis of ³³S/³²S and ³⁶S/³²S in addition to information that can be extracted from ³⁴S/³²S. Variations in the three sulfur isotope ratios (given as δ³⁴S, Δ³³S, and Δ³⁶S) reflect the types of transformations that sulfur species undergo.  For example, the co-variation between δ³⁴S and Δ³³S (or Δ³⁶S) is not the same for equilibrium isotope effects (equilibrium exchange) as it is for isotope effects produced by some metabolic pathways.  The reason of the variations in Δ³³S and Δ³⁶S observed in experiments conducted with microorganisms, which catalyze sulfate reduction and sulfur disproportionation, appears to be the mixing that occurs at the molecular level.

In my presentation, advances and perspectives of analytical protocols for analysis of multiple sulfur isotopes composition of sulfur species in the natural aquatic systems will be discussed. Case studies of the application of multiple sulfur isotopes for studying the sulfur cycles in modern aquatic systems such as Yellowstone National Park hot springs, low-sulfate Lake Kinneret, and seawater Lake Rogoznica, will be presented. Implications of these studies for understanding of sulfur cycling in the ancient oceans will be discussed.