Phylogenetic Estimation of Community Composition and Novel Eukaryotic Lineages in Base Mine Lake: An Oil Sands Tailings Reclamation Site in Northern Alberta

Abstract

Reclamation of anthropogenically impacted environments is a critical issue worldwide. In the oil sands extraction industry of Alberta, reclamation of mining‐impacted areas, especially areas affected by tailings waste, is an important aspect of the mining life cycle. A reclamation technique currently under study is water‐capping, where tailings are capped by water to create an end‐pit lake (EPL). Base Mine Lake (BML) is the first full‐scale end‐pit lake in the Alberta oil sands region. In this study, we sequenced eukaryotic 18S rRNA genes recovered from 92 samples of Base Mine Lake water in a comprehensive sampling programme covering the ice‐free period of 2015. The 565 operational taxonomic units (OTUs) generated revealed a dynamic and diverse community including abundant Microsporidia, Ciliata and Cercozoa, though 41% of OTUs were not classifiable below the phylum level by comparison to 18S rRNA databases. Phylogenetic analysis of five heterotrophic phyla (Cercozoa, Fungi, Ciliata, Amoebozoa and Excavata) revealed substantial novel diversity, with many clusters of OTUs that were more similar to each other than to any reference sequence. All of these groups are entirely or mostly heterotrophic, as a relatively small number of definitively photosynthetic clades were amplified from the BML samples.

Primary Succession Changes the Composition and Functioning of the Protist Community on Mine Tailings, Especially Phototrophic Protists

“…60 Some Excavata have been isolated from various environmental samples such as soils, sediments, and AMD, 41,60 but only a few have been found in the tailing samples. 59 Therefore, our results suggest that the protist Excavata might play important roles in the tailings, especially in bare land. The relative abundances of Archaeplastida and Rhizaria were significantly higher in the BC and MS samples compared to BL (Figure 4).…”

“…This result is in line with prior reports that different stages of primary succession of tailings typically harbor unique microbiomes, though the protistan community was excluded in these studies, 5,29,57,58 except that a dynamic and diverse eukaryotic community containing protists was described in oil sand tailings at Northern Alberta. 59 Our research indicated that the protistan community in tailing samples was predominated by supergroups Archaeplastida, Excavata, Amoebozoa, and Rhizaria (Figure 4). A significantly enriched Excavata group was observed in the BL samples (Figure 4).…”

“…Clear differences were observed among the protistan community in the three stages of tailings as described above (Figure ), suggesting that the primary succession of tailings serves as a strong selection force in shaping the protistan community composition. This result is in line with prior reports that different stages of primary succession of tailings typically harbor unique microbiomes, though the protistan community was excluded in these studies, ,,, except that a dynamic and diverse eukaryotic community containing protists was described in oil sand tailings at Northern Alberta …”

“…The phylogenetic relationship of Excavata members indicated that these members are more diverse than previously thought . Some Excavata have been isolated from various environmental samples such as soils, sediments, and AMD, , but only a few have been found in the tailing samples . Therefore, our results suggest that the protist Excavata might play important roles in the tailings, especially in bare land.…”

Identifying Potential Hosts of Short-Branch Microsporidia

“…The short-branch microsporidians include the partially characterized Paramicrosporidium that are parasites of Saccamoeba limax [8] and Vannella [9], Mitosporidium that are parasites of the crustacean Daphnia [10], as well as Morellospora, an amoeba parasite from the same clade as Mitosporidium [11], and Nucleophaga, a parasite of Thecamoeba [12]. The short-branch microsporidians also include numerous environmental lineages recently uncovered in a re-analysis of a metabarcoding study of Neotropical rainforest soils [5] and other environments [5,13]. Presumably all of these environmental lineages phylogenetically assigned to the short-branch microsporidians are likewise parasitic; it is unknown, though, who are their potential microbial-or macro-organismic hosts, or where to even begin to look for them in environments as species-rich as tropical forests.…”