Microbial Ecology of Subsurface Oil Sands Deposits in Northern Alberta, Canada
Date
2018-08-09
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Abstract
The subsurface Athabasca Oil Sands in northern Alberta, Canada, is an important yet understudied microbial habitat. Over geological time, progressive biodegradation of low molecular weight hydrocarbons by indigenous microorganisms has resulted in an enrichment of high molecular weight hydrocarbons known as bitumen. This is an extreme environment characterized by low water and nutrient availability, thereby resulting in low microbial biomass. The objective of this study was to characterize the microbial ecology of this unique ecosystem, which could ultimately provide a basis for the development of microbially enhanced oil recovery (MEOR) technologies. To that end, pristine core samples were collected from 220 to 320 meters below the surface during 3 annual field trips. Due to the high bitumen and low biomass content of the core samples, extensive method development and validation was performed to identify a robust molecular biological workflow that would allow for consistently successful extraction, amplification and sequencing of genomic DNA from core samples. This molecular biological method was then used to characterize the prokaryotic and eukaryotic microbial communities of the subsurface oil sands through 16S and 18S rRNA gene sequencing. Results revealed a surprising predominance of aerobic and facultative microorganisms in an environment that is traditionally considered anoxic. The genera Pseudomonas, Acinetobacter and Fontibacter were the dominant prokaryotes in all core samples (average relative sequence abundance >5%). Methanoculleus was the only methanogen detected at an average relative sequence abundance >1%. Fungi from the family Trichocomaceae and the order Hypocreales were the prevailing Eukaryotes. Core sample incubations were used to determine the effects of atmosphere and temperature on microbial community succession. Microcosms were established under aerobic, microaerobic and anaerobic atmospheres at reservoir (8°C), mesophilic (33°C) and thermophilic (60°C) temperatures. Results indicate that the predominant community members remained similar to the controls; however, some microcosms incubated at 60°C experienced enrichment of thermophiles, including the genera Thermus, Geobacillus and Thermanaerothrix. Many of the dominant taxa observed in this study could have potential MEOR applications, including hydrocarbon degradation, biosurfactant production and methanogenesis. Thus, the information revealed in this study could be used as the basis for MEOR technologies.
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Keywords
microbial ecology, microbial community analysis, petroleum microbiology, oil sands microbiology, subsurface microbiology, microbially enhanced oil recovery (MEOR)
Citation
Ridley, C. M. (2018). Microbial Ecology of Subsurface Oil Sands Deposits in Northern Alberta, Canada (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/32803