Methane and carbon dioxide produced in peatlands can be held temporarily in dissolved surface
waters and accessible to aquatic plants. The primary peat building plant in northern peatlands,
Sphagnum moss, grows in these dissolved carbon rich waters. Understanding Sphagnum carbon
cycles is key for radiocarbon dating, peatland restoration, and modelling of methane release from
warming peatlands globally. This combined surface and multi‐proxy palaeoenvironmental study
challenges common assumptions about the dissolved gas cycling in this semi‐aquatic environment.
The Sphagnum associated methanotrophic communities within the water filled hyaline cells have
commonly been linked to unusual 13C‐depleted measurements of Sphagnum carbon isotope ratios.
The distinctly 13C‐depleted methane dissolved in surface pool water is traced using isotopic analysis
as it is oxidised and travels into the interstitial Sphagnum water, through to being photosynthetically
captured in α‐cellulose that makes up living Sphagnum, and finally to the carbon stored in layers of
peat. Evidence is presented of a carbon supply available to Sphagnum from both symbiotic
methanotrophs and heterotrophs. Mass balance calculations showed that Sphagnum associated
methanotrophic communities only contribute a small proportion of the carbon fixed by Sphagnum
growing in wet environments despite significant local oxidation. Evidence is presented for the
interstitial Sphagnum water, rich in dissolved carbon dioxide, often being bypassed in favour of the
much faster diffusion of carbon dioxide through air. Combined Sphagnum δ13C and hopanoid
biomarkers in core material showed evidence of a brief period of substantial methane uptake,
however, it is proposed that these events are only detectable in rare instances whereby uptake is
sustained for periods of months to years. This study has demonstrated that an evolving body of
research regarding Sphagnum associated methanotrophs can be applicable in blanket bog habitats.
In the context of methane emissions from peatlands globally, this study indicates that previous
estimates of methane uptake by Sphagnum applied broadly in these landscapes would likely
overestimates the true extent of this process. Nonetheless, the demonstration of methane
oxidation to carbon dioxide in these recently restored sites indicates a resilience of Sphagnum
associated methanotrophic community activity and further evidences of the value in Sphagnum
reintroduction as a host for methane oxidising bacteria in degraded landscapes undergoing
rewetting.
Date of Award | 2023 |
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Original language | English |
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Awarding Institution | |
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Supervisor | Tim Daley (Other Supervisor) |
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- sphagnum
- peatland
- palaeoecology
- palaeoenvironmental
- testate amoebae
- carbon cycles
- hopanoid biomarkers
- carbon isotopes
- Dartmoor National Park
An Isotopic Analysis of Carbon Dynamics in Sphagnum Peat
Newman, J. M. (Author). 2023
Student thesis: PhD