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UBC Theses and Dissertations

Concentrations and turnover rates of reduced sulfur compounds in polar and sub-polar marine waters : field application of novel analytical and experimental techniques Asher, Elizabeth Colleen


Dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP) and dimethyl sulfoxide (DMSO) are ubiquitous in surface marine environments. These reduced sulfur compounds are crucial to the physiological ecology of bacteria and phytoplankton. DMS also has a role in climate regulation, as a source of aerosols that back-scatter incoming solar radiation. This thesis aims to characterize the processes driving DMS/P/O accumulation in polar and sub-polar marine waters. Chapters two and three document DMS/P/O concentrations in surface waters of the Subarctic Northeast Pacific, using automated measurement systems. These studies employed an existing system based on membrane inlet mass spectrometry (MIMS) and a novel automated system for the sequential analysis of DMS/P/O (OSSCAR; see chapter three). DMS/P/O concentrations demonstrate significant spatial variability over a range of scales in both coastal and open ocean waters, revealing relationships with key oceanographic variables. Chapter four describes the first application of a recently developed, stable isotope tracer technique using purge and trap capillary inlet mass spectrometry (PT-CIMS) in Antarctic sea-ice. This chapter documents extremely rapid DMS/P/O turnover in sea-ice brines and demonstrates a previously unrecognized role for DMSO, as well as DMSP, as important sources of DMS in these environments. Chapters five and six use MIMS, PT-CIMS, and OSSCAR in parallel to examine DMS/P/O cycling in the Subarctic Northeast Pacific, and in coastal waters of the Western Antarctic Peninsula (WAP). Chapter five focuses on the spatial distribution of DMS accumulation and net production in the Subarctic Pacific, while chapter six follows the seasonal changes in DMS/P/O concentrations and its production in the WAP, and highlights short-scale temporal variability of DMS/P/O. Results demonstrate strong spatial gradients in DMS production and consumption terms (higher values in near-shore waters) in the Subarctic Pacific, and showed that net DMS production predicts DMS accumulation in surface waters. Over the seasonal cycle in the WAP, zooplankton grazing and DMSP cleavage dominated DMS production, and bacterially mediated DMS consumption controlled the removal of DMS in surface waters.

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