Albakistani, EmadNwosu, Felix ChinweijeFurgason, Biegler, ChantelHaupt, Evan S.Smirnova, Angela V.Verbeke, TobinLee, Eun-SukKim, Joong-JaeChan, AmeliaRuhl, Ilona A.Sheremet, AndriyRudderham, Sarah B.Lindsay, Matthew B. J.Dunfield, Peter2022-09-272022-09-272021-11-24Albakistani, E.A., Nwosu, F. C., Furgason, C., Haupt, E. S., Smirnova, A. V., Verbeke, T. J., Lee, E.-S., Kim, J.-J., Chan, A., Ruhl, I. A., Sheremet, A., Rudderham, S. B., Lindsay, M. B. J. & Dunfield, P. F. (2022). Seasonal dynamics of methanotrophic bacteria in a boreal oil sands end pit lake. Applied and Environmental Microbiology, 88(3), e0145521. https://doi.org/10.1128/aem.01455-21https://hdl.handle.net/10388/14233Copyright © 2022 American Society for Microbiology. All Rights Reserved.Base Mine Lake (BML) is the first full-scale demonstration end pit lake for the oil sands mining industry in Canada. We examined aerobic methanotrophic bacteria over all seasons for 5 years in this dimictic lake. Methanotrophs comprised up to 58% of all bacterial reads in 16S rRNA gene amplicon sequencing analyses (median 2.8%), and up to 2.7 × 104 cells mL−1 of water (median 0.5 × 103) based on qPCR of pmoA genes. Methanotrophic activity and populations in the lake water were highest during fall turnover and remained high through the winter ice-covered period into spring turnover. They declined during summer stratification, especially in the epilimnion. Three methanotroph genera (Methylobacter, Methylovulum, and Methyloparacoccus) cycled seasonally, based on both relative and absolute abundance measurements. Methylobacter and Methylovulum populations peaked in winter/spring, when methane oxidation activity was psychrophilic. Methyloparacoccus populations increased in the water column through summer and fall, when methane oxidation was mesophilic, and also predominated in the underlying tailings sediment. Other, less abundant genera grew primarily during summer, possibly due to distinct CH4/O2 microniches created during thermal stratification. These data are consistent with temporal and spatial niche differentiation based on temperature, CH4 and O2. This pit lake displays methane cycling and methanotroph population dynamics similar to natural boreal lakes.enmethanemethanotrophstratified lakedimictic lakeland reclamationend pit lakemethanotrophsArticle10.1128/aem.01455-21