Abstract
Peat represents a globally significant pool of sequestered carbon. However, peatland carbon stocks are highly threatened by anthropogenic climate change, including drought, which leads to a large release of carbon dioxide. Although the enzymatic mechanisms underlying drought-driven carbon release are well documented, the effect of drought on peatland microbial communities has been little studied. Here, we carried out a replicated and controlled drought manipulation using intact peat ‘mesocosm cores’ taken from bog and fen habitats, and used a combination of community fingerprinting and sequencing of marker genes to identify community changes associated with drought. Community composition varied with habitat and depth. Moreover, community differences between mesocosm cores were stronger than the effect of the drought treatment, emphasising the importance of replication in microbial marker gene studies. While the effect of drought on the overall composition of prokaryotic and eukaryotic communities was weak, a subset of the microbial community did change in relative abundance, especially in the fen habitat at 5 cm depth. ‘Drought-responsive’ OTUs were disproportionately drawn from the phyla Bacteroidetes and Proteobacteria. Collectively, the data provide insights into the microbial community changes occurring alongside drought-driven carbon release from peatlands, and suggest a number of novel avenues for future research.
Highlights
Anthropogenic climate change is one of the key issues of the 21st century, with the potential to severely impact human lives as well as natural ecosystems[1]
While protozoa have been neglected in modern-day studies of drought effects on peatland microbial communities, paleoecological studies indicate that testate amoebae community composition in peat is strongly influenced by water table depth[30]
automated ribosomal intergenic spacer analysis (ARISA) fingerprinting of bacterial communities yielded bands ranging in size from 110–2839 bp, while ARISA fingerprinting of fungal communities yielded bands ranging from 54–2851 bp
Summary
Anthropogenic climate change is one of the key issues of the 21st century, with the potential to severely impact human lives as well as natural ecosystems[1]. While climate change models project an increase in total precipitation at high latitudes, rainfall is likely to become more concentrated in extreme events interspersed with periods of dry weather[19], while higher temperatures will increase water loss from soils[20] Together, these effects will lead to an increase in the likelihood of drought events[19, 20] and a fall in peatland summer water table[21, 22]. In order to identify changes in microbial communities which occur concurrently to the release of carbon from peat ecosystems, here we aimed to use high-throughput marker gene sequencing to identify the proportion of the microbial biosphere which is affected by drought and rewetting in bogs and fens, two habitats which are representative of the majority of temperate peatlands in the Northern hemisphere. ARISA fingerprinting was followed by sequencing, bioinformatics and statistical analysis of 16S and 18S rRNA genes to obtain a more detailed perspective of community changes
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