ORGANIC SULFONES IN THE BRINE OF LAKE VIDA (EAST ANTARCTICA)

Abstract Located in a closed basin in the McMurdo Dry Valleys, East Antarctica, Lake Vida brine is a cold (-13°C), hypersaline, interstitial, anoxic, and aphotic ecosystem trapped within 27+ m of ice. This brine is not in contact with the atmosphere, and currently hosts a slow-growing, cold-limited bacteria-dominated ecosystem that have persisted for at least ∼2800 years. Analysis of the dichloromethane extractable fraction of dissolved organic matter of Lake Vida brine revealed the presence of seven novel organic sulfones, tentatively identified on the basis of mass spectral fragmentation, as well as eight sulfones that have been structurally described in previous chemistry studies. A total of fifteen organic sulfones, and others that have yet to be identified, were observed in Lake Vida brine, most of which have never been previously detected in any other natural ecosystems. Results suggest that these compounds may be derived from a lake system in which a dissolved organic carbon pool may have been oxidized in lake waters in contact with the atmosphere. Alternative hypotheses on the origin of these sulfones, involving potential abiotic alterations of dissolved organic sulfur as a consequence of long-term brine-rock reactions that generated reactive oxygen species, are also considered. Understanding the origin and formation mechanisms of these organic sulfones may reveal an important pathway that influence the dissolved organic sulfur constituent, not only of Antarctic aquatic systems, but also potentially the global marine environment, as well as extraterrestrial hypersaline, subzero habitats.