Novel stable isotope and biomarker approaches to measuring methane emission in peat bogs

Novel stable isotope and biomarker approaches to measuring methane emission in peat bogs

Supervisor: Dr. Caroline Gauchotte-Lindsay, University of Glasgow (caroline.gauchotte-lindsay@glasgow.ac.uk); Dr Jaime Toney, University of Glasgow (Jaime.toney@glasgow.ac.uk); Prof. David Graham, Newcastle University (david.graham@ncl.ac.uk)

Description: This is an IAPETUS studentship: IAPETUS is the North East of England’s and Scotland’s multidisciplinary Doctoral Training Partnership (DTP) for the environmental sciences, which is funded and accredited by NERC. More information can be found here: http://www.iapetus.ac.uk

Methane (CH4) is a greenhouse gas that is 25-times more potent than CO2 at trapping heat at the Earth’s surface. Methane emissions from peatlands represent ≈10% of the total methane flux to the atmosphere. Under projected climate change scenarios, peats are expected to increase their contribution to atmospheric CH4. Methane is produced by methanogenic microorganisms in the permanently saturated lower layers of peat while it is consumed by methanotrophic microorganisms primarily in the upper aerobic layers. An understanding of the mechanisms for the mediation between methanogenic and methanotrophic activities is crucial to fully comprehend the processes that abate CH4 emissions from peatland.  Diploptene is a methanotroph membrane lipid, whose concentration linearly increases with methane emission. This project aims to develop and assess a unique and novel stable isotope tool to elucidate how the carbon isotopic signature of this methanotroph biomarker is associated to methane availability as a carbon source in peat

Compound-specific stable isotope analysis (CSIA) is transforming environmental research, as evidenced by the exponential increase since 1995 in citations of peer-reviewed papers using the technique (i.e. 1500 to ~14,000). Notably, carbon CSIA has been employed to elucidate processes of microbial-mediated CH4 release from soils/peat in modern and ancient environments.

The concentration of the methanotroph biomarker diploptene correlates positively with methane emission in peats, while its carbon stable isotopic values (δ13C) were also shown to correlate with both methane production and consumption and to change in response to the source of methane. To further develop the use of diploptene as a biomarker for methane oxidation, it is crucial to understand how its δ13C is related to the δ13C of the possible carbon sources and particularly methane. This project will assess how the δ13C values of individual carbon atoms within the molecule contribute to the overall signature preserved in the environment through the development of an on-line position specific stable isotope analysis (PSIA) method for diploptene and its use for the characterisation of both planned cultures and field samples. In particular, the δ13C values of the CH3 groups attached to the ringed backbone of diploptene are expected to be closely related to that of the source methane. The student will adapt the current on-line PSIA technology to isolate the CH3 group in diplotene molecules and measure their carbon stable isotope signatures.

Then, the student will initially perform lab-based growth experiments on methanotroph cultures grown under different conditions, such as high/low methane, high/low oxygen, high/low nitrogen, high/low copper. The changes in the CSIA and PSIA δ13C of diploptene will be monitored. Secondly, the student will collect modern peat samples from the aerobic section of a Scottish peatland, Black Law, and analyse the CSIA and PSIA δ13C values of diploptene. Black Law is an ideal site for collection of natural samples for comparison with the laboratory cultures, because methane efflux, water table depth and a suite of other metadata are available to help with results analysis.

The combination of comprehensive stable isotope data for planned cultures and field samples will provide unique and crucial insights to the assimilation of source methane in lipid biomarkers and the information it provides about the methane flux.

Earth history. Gaines, Eglinton, and Rullkötter, 2009. Oxford Press. pp. 355

Kip et al. (2010) Nature Geoscience, doi:10.1038/ngeo939

Gauchotte et al. (2009) RCM, doi:10.1002/rcm.4222

Gauchotte-Lindsay and Turnbull (2016) TrAC, doi: https://doi.org/10.1016/j.trac.2015.07.010

Further details can be found here:  http://www.iapetus.ac.uk/iap-17-48-novel-stable-isotope-and-biomarker-approaches-to-measuring-methane-emission-in-peat-bogs/

Funding notes: Funding is available to cover Home tuition fees, as well as paying a stipend at the Research Council rate (estimated £14,553 for Session 2017-18).

Eligibility: All applicants need to meet NERC’s eligibility criteria to be considered for an IAPETUS studentship and these are detailed in the current RCUK studentship terms and conditions.

IAPETUS is only able to consider applications from Home/European Union candidates. International candidates are not eligible to be considered and where an candidate from another EU country has not been resident in the UK for 3 years or more prior to the commencement of their studies with IAPETUS, they will only be eligible for a fees-only studentship.

How to Apply: Please refer to the following website for details on how to apply:

http://www.gla.ac.uk/research/opportunities/howtoapplyforaresearchdegree/.

When applying you will need to complete their online postgraduate application form and state that you wish to be considered for an IAPETUS studentships when prompted how you intend to fund your postgraduate studies and highlight the specific doctoral research project that you wish to be considered for, quoting the doctoral research project’s reference (which are quoted in each doctoral research project’s brief) where possible.

In addition to completing an online application form, you will also need to provide the following documentation to your prospective Department/School:

  1. Current CV;
  2. A cover letter, no longer that 2 pages of A4 in length, detailing your reasons for applying for a PhD and why you have selected your chosen doctoral research project;
  3. Two references, where possible not from your prospective supervisor(s); &
  4. Transcripts of your previous qualifications obtained to date.

Deadline: 19 January 2018

Start Date: October 2018