Microbial communities and methane oxidation processes in Base Mine Lake, a model end-pit lake in the Alberta oilsands

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One challenge facing the oilsands industry in Canada is reclaiming mining-impacted environments, especially areas affected by tailings produced during bitumen extraction. The tailings contain various chemical constituents (mainly salts and organic molecules such as naphthenic acids), and can produce methane. At present tailings are usually stored on open basins known as tailings ponds. The long-term land reclamation plans of several mining operations include the construction of End-Pit Lakes (EPLs). These are below-grade bodies of water in surface mining pits that will eventually become integrated into local watersheds. They should function in long-term containment and remediation of tailings material. Although EPLs have been designed and applied in other mining operations, none presently exist in the Alberta oilsands. Syncrude is developing Base Mine Lake (BML) as their pilot EPL project. BML was previously an active tailings pond which ceased to receive fresh tailings input in 2012 and began to receive fresh water in 2013. BML is a pilot test system for the EPL concept, so increasing our understanding of fundamental processes occurring in the lake is critical. Syncrude is sponsoring a diverse research program for BML in order to understand these processes, including how the biology and biogeochemistry of the system develops after tailing pond closure and water-capping. Our specific study within the BML research program will monitor some key microbial processes during the first few years of reclamation. The primary goal is to develop a better understanding of methane-metabolising bacteria in BML, and how these bacteria affect: i) the dissolved oxygen concentrations in the lake, a key factor determining the habitibility of the water for higher organisms, and ii) bioremediation of organic and inorganic constituents. A secondary goal is to monitor overall microbial communities in the lake using DNA-based methods, in order to develop indicators of the reclamation progress and to develop best practices for later EPL development.