MSc in Applied Science Thesis Defence

Elish Redshaw

'The Microbial and Geochemical Architecture of Scotian Slope Cold Seep Site 2A-1, Scotian Slope, Canada'

Abstract: Cold seeps, occur globally along the seabed of continental margins. These sites are identified by the reduced fluids they expel, which helps to form oasis-like ecosystems in highly redox stratified sediments that are unique compared to the surrounding seafloor. In this study, using a remotely operated vehicle, a 600 m long, six push core, transect was collected from cold seep site 2A-1, located on the Scotian Slope of Eastern Canada. Downcore porewater ions and lipidomic profiles were generated.  These data were compiled as spatially resolved, two-dimensional heatmaps to examine both vertical and lateral changes in the subsurface geochemical and microbiological architecture of the seep structure. Twenty-three lipid classes, predominantly of archaeal origin, were tentatively identified and quantified. Microbially mediated metabolic zones of denitrification, microbial sulfate reduction, anaerobic methane oxidation, and methanogenesis were then mapped across the seep based on ion pore water concentrations and diffusion fluxes, carbon isotope values, lipidomic diversity patters, and biomarker proxy data. The resolved lipidome indicates the archaeal community is heavily zoned with diversity increasing as a function of seepage rate. The results also provide insights into seep evolution and its impact on microbial zonation dynamics across the seep structure.

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