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Abstract BIOGEOCHEMICAL CYCLING OF ORGANIC SULFUR IN ANTARCTICA David J. Kieber1, Ronald
P. Kiene2, Dierdre A. Toole3, Polar Regions have very high seasonal phytoplankton biomass and primary production. Associated with these blooms are some of the world’s highest concentrations of algal-derived dimethylsulfoniopropionate (DMSP), its degradation product, dimethyl sulfide (DMS), and dimethyl sulfoxide (DMSO). These sulfur compounds are part of a biogeochemical system that transfers sulfur from the oceans to the atmosphere, via volatile DMS, which can affect cloud microphysics and climate. DMSP also represents up to 60% cellular sulfur; and, even more significantly, up to 16-20% of the cellular C content in such species as Phaeocystis antarctica, making it an important contributor to the Antarctic sulfur and carbon cycles. Despite the importance of organosulfur to marine ecology and climate, rates of organosulfur transformations are poorly characterized in Antarctic waters, especially during massive colonial blooms of the DMSP-producing P. antarctica. In order to better understand the processes controlling sulfur dynamics during the development and decay of P. Antarctica, we conducted two cruises in the Ross Sea wherein we quantified rates of microbial, algal and non biological processes related to the formation and loss of various sulfur species in the upper water column. Highlights of our cruises that illustrate the significance of DMS(P) and related compounds in the seasonal bloom of Phaeocystis antarctica will be discussed along with associated implications for carbon and sulfur cycling in these waters.
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