Peatland microbial community structure and function along a metal contamination gradient in Sudbury, Ontario

Abstract

The Sudbury, Ontario region has had over a century of metal mining/smelter activity that has led to significant sulphur and metal deposition and this has negatively affected both freshwater and terrestrial ecosystems, including peatlands. Peatlands store organic materials, regulate nutrient turnover and act as a carbon sink for global climate change, yet relatively little is known in regards to the impact of the mining legacy of this region and the potential microbial communities affected. Eleven peatland sites (poor to intermediate fens) around Sudbury were chosen in order to study the microbial diversity and function that control decomposition and nutrient cycling. The analysis of microbial communities was accomplished via high-throughput sequencing of 16S rRNA genes in bacteria and archaea on the Illumina MiSeq platform, while the analysis of microbial function was conducted through the Sinsabaugh enzyme protocol and gas chromatography of in situ greenhouse gases. There was a difference across the site gradient with microbial diversity, community structure, and microbially mediated gas efflux differing between areas closest to current and historical smelters to areas 55-km away. There was also a difference within each peatland where vertical profiles in microbial enzyme function varied over four depths, with the surface depth having the highest enzyme activity. Metal impact and pH are major drivers of microbial diversity and community with pH driving metal availability. This is seen where the sites with the lowest pH having the lowest microbial diversity and unique communities, and sites with the highest pH having the highest microbial diversity and distinct communities. We can also deduce that microbial function differs over depth because of the difference between the aerobic and the anaerobic communities, where the aerobic communities appear to be more active. We can reason that methane efflux was higher in impacted sites because of the increased concentrations of Nickel, Copper, pH and possibly Sulphur creating restrains on microbially mediated gas effluxes through the inhibition of methane production.