Browsing by Author "Davidson, Hanna Elise"

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    Anaerobic Methanotrophy in an Oil Sands End Pit Lake
    (2024-08-23) Davidson, Hanna Elise; Dunfield, Peter; Siddique, Tariq; Hubert, Casey; Stein, Lisa
    Albertan oil sands, and even oil sands reclamation projects, emit large volumes of greenhouse gases. Methane is one of the most potent greenhouse gases, and aerobic methane oxidation has been a subject of interest for methane mitigation. However, anaerobic oxidation of methane (AOM) may be just as influential in reducing methane emissions, as concerns with excess methane emissions and sediment disturbance by ebullition remain. Oil sands end pit lakes, made to reclaim tailings as well as mined-out pits, may be prime environments for AOM. This project determined if AOM was occurring in the first demonstration-scale oil sands end pit lake and attempted to determine the microbial communities facilitating this process. The potential of adding electron acceptors to sediment to increase rates of AOM was also investigated. We determined that AOM was occurring in the oil sands end pit lake’s sediment, using 13CH4-spiked incubations. We estimate that overall, AOM rates fall between 0.07-0.51 nmol mL-1 d-1 in the natural sediment. Incubations showed that AOM was most active within the first 100 days of methane-rich incubation. Electron acceptor amendments did not affect rates universally, although ferrihydrite amendments did stimulate 13CO2 production rates of up to 0.15 nmol mL-1 d-1 and may extend the longevity of high AOM rates. Effects of electron acceptor addition appear to be very site- and depth- specific and this may indicate that there are microhabitats ideal for AOM. The microbial communities responsible for AOM remain elusive. Known anaerobic methane-oxidizing taxa were identified only in minute abundances and did not detectably increase in abundance, even after 150 days of incubation. Methane oxidation rates recorded in incubations were comparable to the methane oxidation rates known for both methanogenic trace methane oxidation and anaerobic methane oxidation. This work is an initial assessment of AOM in oil sands end pit lakes, providing a base for the next steps for understanding AOM. Studying AOM rates to better illustrate methane emissions will be instrumental in managing tailings ponds and end pit lakes. This work could also have a substantial impact on microbial biodiversity knowledge, particularly in the understanding of the communities impacting freshwater AOM.