Bacterial Community Composition in the Water Column of a Lake Formed by a Former Uranium Open Pit Mine
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Mining of pyrite minerals is a major environmental issue involving both biological and geochemical processes. Here we present a study of an artificial lake of a former uranium open pit mine with the aim to connect the chemistry and bacterial community composition (454-pyrosequencing of 16S rRNA genes) in the stratified water column. A shift in the water chemistry from oxic conditions in the epilimnion to anoxic, alkaline, and metal and sulfide-rich conditions in the hypolimnion was corresponded by a strong shift in the bacterial community, with few shared operational taxonomic units (OTU) between the water layers. The epilimnetic bacterial community of the lake (∼20 years old) showed similarities to other temperate freshwater lakes, while the hypolimnetic bacterial community showed similarity to extreme chemical environments. The epilimnetic bacterial community had dominance of Actinobacteria and Betaproteobacteria. The hypolimnion displayed a higher bacterial diversity and was dominated by the phototrophic green sulphur bacterium of the genus Chlorobium (ca. 40 % of the total community). Deltaproteobacteria were only represented in the hypolimnion and the most abundant OTUs were affiliated with ferric iron and sulfate reducers of the genus Geobacter and Desulfobulbus, respectively. The chemistry is clearly controlling, especially the hypolimnetic, bacterial community but the community composition also indicates that the bacteria are involved in metal cycling in the lake.
KeywordsBacterial Community Acid Mine Drainage Actinobacteria Operational Taxonomic Unit Ribosomal Database Project
We thank Jörgen Ek and Karin Holm (Dep. of Applied Environmental Science, Stockholm University), and Klara Hajnal and Magnus Mörth (Dep. of Geological Sciences, Stockholm University) with the valuable help with analysis of nitrate and ammonium, anions using ion chromatography and metals by using ICP-OES and ICP-MS, respectively. Many thanks are due to Anna Hägglund for the assistance in the field and the laboratory. We also acknowledge Volker Brüchert (Dep. of Geological Sciences, Stockholm University) for commenting and improving the manuscript. A.F.A. and S.J.M.H. were supported by grants from the Swedish research council Formas. The pyrosequencing as well as many of the chemical analysis were financed by grants from Carl Tryggers research foundation.
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