Long-term effects of air pollution on microbial communities of moorland peat

Upland peatlands receive the majority of their ecosystem inputs through precipitation, which delivers not only moisture but also atmospheric gases and particulates. Pristine peatlands are characterised by nutrient limitation, leading to the establishment of oligotrophic organism communities both above- and below-ground. Sphagnum mosses in particular thrive, and their presence promotes peat formation. The moorlands of the Southern Pennines have been subjected to long-term heavy metals deposition following the industrial revolution, and the peat-forming process has been halted by a major loss of Sphagnum. As a result, high levels of deposited heavy metals remain in the surface horizon and may be continuing to inhibit establishment of sensitive oligotrophic organisms many years after atmospheric heavy metals pollution was brought under control. Natural processes and restoration activities have re-vegetated large areas of previously bare peat, and these exhibit much lower heavy metals concentrations compared to stable long-term vegetated areas because the polluted surface horizon has been eroded away. The resulting vegetation and pollution patchwork provides a unique opportunity to assess the impact of long-term (>200 years) air pollution on the peatland ecosystem.

Soil microbes deliver myriad ecosystem services in the soil, including plant growth promotion, nitrogen fixation, and decomposition. These activities are a function of the collective microbial genomes present, which can now be evaluated using a variety of high-throughput DNA sequencing techniques. We used a taxonomic marker gene approach to identify bacteria and fungi associated with historical airborne deposition of heavy metals. A unique microbial community was associated with heavy metals impacted sites, which is likely to be reflected in altered functional properties of the soil. We identify candidate marker microbes for heavy metals contamination, and investigate potential ecosystem impacts by detecting displacement of microbes associated with the legacy of airborne pollution at Holme Moss in the Southern Pennines.

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