Sea ice microbial communities produce large amounts of the sulfur metabolite dimethylsulfoniopropionate (DMSP), a precursor of the climate cooling gas dimethylsulfide. Despite their importance to the polar sulfur cycle, drivers and metabolic pathways of sea ice DMSP are uncertain. Here we report the first measurements of sea ice DMSP sulfur isotopic composition (34S/32S ratio, δ34S). δ34S values in ice cores from the Ross Sea and Weddell Sea reveal considerable variability across seasons and between ice horizons (from +10.6 to +23.6‰). We discuss how the most extreme δ34S values observed could be related to unique DMSP cycling in the seasonally extreme physiochemical conditions of isolated brine inclusions in winter-spring. Using cell cultures, we show that part of the DMSP δ34S variability could be explained by distinct DMSP metabolism in sea ice microalgae. These findings advance our understanding of the sea ice sulfur cycle and metabolic adaptations of microbes in extreme environments.
Bibliographical noteFunding Information:
The authors thank the captain and crew of the RV Polarstern and Nathaniel B. Palmer as well as Chief Scientist Dr. Peter Lemke, and Dr. Steve Ackley for their unconditional logistic and scientific support during the AWECS and PIPERS cruise. The authors would also like to thank the Scott Base crew, Antarctica New-Zealand, and Dr. Tim Haskell for their logistic and scientific support during the YROSIAE study, and Alex Meshoulam (HUJI) for the S isotope analysis of the sulfate samples. G.C. benefited from a Belgian FNRS research grant (contract A 4/5 – MCF/DM – 2657). This paper is a contribution to the BIGSOUTH BELSPO (Belgian Science Policy Office) project. Ocean data view (ODV) 4.7.10 free software was used for mapping in this study (Schlitzer, R., http://odv. awi.de, 2016).
© 2018, The Author(s).