The Response of Microbial Communities to Peatland Drainage and Rewetting. A Review.

Ezra Kitson,Nicholle G A Bell

doi:10.3389/fmicb.2020.582812

Abstract

Peatlands are significant global carbon stores and play an important role in mediating the flux of greenhouse gasses into the atmosphere. During the 20th century substantial areas of northern peatlands were drained to repurpose the land for industrial or agricultural use. Drained peatlands have dysfunctional microbial communities, which can lead to net carbon emissions. Rewetting of drained peatlands is therefore an environmental priority, yet our understanding of the effects of peatland drainage and rewetting on microbial communities is still incomplete. Here we summarize the last decade of research into the response of the wider microbial community, methane-cycling microorganisms, and micro-fauna to drainage and rewetting in fens and bogs in Europe and North America. Emphasis is placed on current research methodologies and their limitations. We propose targets for future work including: accounting for timescale of drainage and rewetting events; better vertical and lateral coverage of samples across a peatland; the integration of proteomic and metabolomic datasets into functional community analysis; the use of RNA sequencing to differentiate the active community from legacy DNA; and further study into the response of the viral and micro-faunal communities to peatland drainage and rewetting. This review should benefit researchers embarking on studies in wetland microbiology and non-microbiologists working on peatland drainage and rewetting in general.

Highlights

Peatlands cover ∼2.84% of the world’s land area yet account for a significant proportion of terrestrial carbon (Batjes, 1996; Xu et al, 2018)
Some peatlands have suffered additional destructive alteration such as fire (Swindles et al, 2016), nutrient deposition (Elliott et al, 2015) and mining (Andersen et al, 2013b; Basiliko et al, 2013; Reumer et al, 2018) which will influence the microbial communities in specific ways (Table 1; Andersen et al, 2013a); this can be evidenced by the extreme dysfunctionality in microbial activity and community composition observed in bare peat (Andersen et al, 2013b; Elliott et al, 2015)
11 of the 21 studies we reviewed did not account for depth in their experimental design, which may have obscured changes in community composition and microbial activity caused by drainage, given that the main changes are likely to occur below the surface at the oxic-anoxic boundary

Summary

Introduction

Peatlands cover ∼2.84% of the world’s land area yet account for a significant proportion of terrestrial carbon (Batjes, 1996; Xu et al, 2018). Peatlands act as a carbon sink due to low rates of decomposition leading to the accretion of partially decayed plant matter. Due to their ability to sequester carbon dioxide, peatlands play an important role in mitigating against global climate warming. In the 20th century peatlands faced anthropogenic alteration on a significant scale, and many were drained in order to repurpose the land for agricultural and industrial use. Based on data from the Greifswald Mire Centre (2015), 527,783 km of peatland had been drained, most of which occurred in Europe.

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Conclusion