Context. The Alberta oil sands industry has amassed over 1 trillion litres of fluid tailings containing toxic compounds such as naphthenic acids. End-pit lakes have been proposed as a long-term reclamation strategy and Base Mine Lake (BML) is the only full-scale end-pit lake in the Canadian oil sands industry. Established in 2012, BML contains about 170 Mm3 of permanently placed fluid tailings physically sequestered below the mudline. A freshwater cap overlies the fluid tailings and water quality is expected to improve over time. The water cap supports a microbial community that is expected to biodegrade naphthenic acids and other residual hydrocarbons from tailings porewater.
Gap. Although the phototroph community is fundamental to ecological development in BML, no research has been published on this topic yet.
Aim. Characterize and quantify the phototroph community over time in BML from 2015-2019 and identify phototroph interactions with the microbial community.
Methods. Sampling of the BML water cap occurred from 2015-2019. Characterization of the microbial community was completed using gene amplicon sequencing targeting the 16s, 18s, and 23s ribosomal RNA genes to respectively identify bacteria, eukaryotes, and cyanobacteria and chloroplast-bearing organisms. Phototrophic abundance was quantified using qPCR targeting the 23s rRNA gene. Phototrophic interactions have been identified using a co-occurrence network analysis based on sequencing data.
Findings. Sequencing analysis indicates major phototrophic members of the microbial community include Cryptomonasspp. (Cryptophyceae), Choricystis spp. (Trebouxiophyceae), Euglena spp. (Euglenales), and Cyanobium spp. (Synechococcales). 23s rRNA qPCR results indicate an increase in phototroph abundance from 2015-2019. Network analyses (Figure 1) indicates certain phototrophs are integral to BML's microbial community. For example, Choricystis parasitica has 13 connections in the autumn network.
Utilization. This project will contribute to research on oilsands tailings reclamation and phototroph ecology in engineered oilsands tailings environments.
