The influence of hydrogeological disturbance and mining on coal seam microbial communities

The microbial communities present in two underground coal mines in the Bowen Basin, Queensland, Australia, were investigated to deduce the effect of pumping and mining on subsurface methanogens and methanotrophs. The micro-organisms in pumped water from the actively mined areas, as well as, pre- and post-mining formation waters were analyzed using 16S rRNA gene amplicon sequencing. The methane stable isotope composition of Bowen Basin coal seam indicates that methanogenesis has occurred in the geological past. More recently at the mine site, changing groundwater flow dynamics and the introduction of oxygen in the subsurface has increased microbial biomass and diversity. Consistent with microbial communities found in other coal seam environments, pumped coal mine waters from the subsurface were dominated by bacteria belonging to the genera Pseudomonas and the family Rhodocyclaceae. These environments and bacterial communities supported a methanogen population, including Methanobacteriaceae, Methanococcaceae and Methanosaeta. However, one of the most ubiquitous micro-organisms in anoxic coal mine waters belonged to the family 'Candidatus Methanoperedenaceae'. As the Archaeal family 'Candidatus Methanoperedenaceae' has not been extensively defined, the one studied species in the family is capable of anaerobic methane oxidation coupled to nitrate reduction. This introduces the possibility that a methane cycle between archaeal methanogenesis and methanotrophy may exist in the anoxic waters of the coal seam after hydrogeological disturbance.