PRESENTER:

Gamra Oueslati:

“Comprehensive Organic Geochemical and Geophysical Surveys of Marine Microbial Communities within the Scotian Slope Cold Seeps, Nova Scotia, Canada”

Supervisor: Dr. Todd Ventura

Internal Committee Members: Dr. Linda Campbell and Dr. Robert Singer

Abstract: This research aims to understand microbial communities’ abundance and distribution within the Scotian Slope as a means of cold seep detection by using lipidomic proxies. These approaches are used to complement microbiological and geophysical data to understand how the local microbiome is impacted by seepage events at a spatial scale of 10s of km within the Scotian Slope. Through this project, we hope to get a clear picture of microbial sources and metabolisms that may help detect organic matter origins and hydrocarbon migration through faulting systems. The thesis can be divided into three main studies. The first study detects the distribution of various lipid classes within the water column and surface sediments from two cold seep sites within the Scotian Slope. This lipidomic study is combined with a porewater geochemical survey to help differentiate upper water column lipid loading from in situ production within the ocean floor surface sediments. The second study focuses on the chemotaxonomic identification of microbial communities over time and space based on the quantification of lipids from sediments collected from three perspective seep sites identified, in part, by the presence of geophysical direct hydrocarbon indicators (DHIs) and to understand the spatial distribution and changes of the hosted community into more deeply buried sedimentary paleoenvironments. The third study supports microbial communities’ investigation in terms of composition and metabolism by combining menaquinones and lipids analysis from all the previously mentioned water column and core sediment samples.

Key Words: Scotian Slope, hydrocarbon seeps, direct hydrocarbon indicators, water column, organic matter loading, menaquinones, Thaumarcheoata, lipidomics, chromatography, spectrometry, seismic anomalies, spatial interpolation.