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PhD in Geographical & Earth Science – ‘Size isn’t everything: The role of small water bodies in aquatic-atmopshere methane exchange’.


   College of Science and Engineering

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  Dr A Bass, Dr Brian Barrett, Dr Jens Subke  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

Glasgow United Kingdom Environmental Biology Environmental Chemistry Environmental Geography

About the Project

Methane (CH4) is 34 times more potent than carbon dioxide (CO2) as a greenhouse gas (GHG) and is a key component of the global C-cycle. Emissions from inland water bodies are a key pathway for methane flux and while significant, estimates of CH4 fluxes from surface waters are still highly uncertain with error bars up to ± 90 % (Saunois et al. 2016). This uncertainty stems from multiple avenues, including the variable balance between diffusive and ebullitive (bubble) fluxes, as well as the spatiotemporal variability within and between water bodies. A critical unknown is the role small water bodies (ponds, ditches, drains, etc) play in these dynamics, though initial evidence suggests they are disproportionately important (Quinn et al. 2019). This project will quantify CH4 fluxes from a range of small water bodies, determine spatial-temporal dynamics and elucidate controlling factors. Combined with a remote sensing approach to surface water mapping it will fill a critical gap in our current understanding, better equipping scientists and policy makers to manage these systems for maximum carbon benefit.

Small inland water bodies have a disproportionate impact in terms of CH4 emissions per unit surface area. For example, small water bodies (<0.001 km2) may account for up to 40% of CH4 emissions from global lakes / ponds (which together contribute 60% of the global natural CH4 flux), despite accounting for only 8.6 % of the global lake surface area (Holgerson & Raymond 2016). Critically, these estimates of CH4 emissions, while significant are limited temporally and spatially and based almost exclusively on diffusive CH4 fluxes from a limited number of sites. If we include ebullition fluxes this will potentially increase the contribution of CH4 from small water bodies substantially, but currently very little spatial and temporal coverage of ebullition measurements is available, and for this reason ebullition has often been excluded from reviews of the global CH4 budget.

Though small, these small inland water bodies can still show significant intra- and inter-lake spatial variation. Aspects such as temperature, organic matter supply to the sediment and water depth will change across a lake cross section, each of which can change the rates of both methanogenesis, and subsequent gas flux. Temperate lakes in Europe recorded maximum ebullition in the central regions due to pronounced stratification and stronger anoxia in the deep-water layers (Schilder et al. 2016). In contrast, small lakes in Siberia and Alaska showed the opposite pattern, with maximum flux at the lake edge, due to proximity to the permafrost edge and organic-C availability (Walter et al. 2008). Quantifying this variation is critical alongside the interaction with critical co-drivers – aspects that this project will address through the following objectives:

i)              Deploy a network of CH4 ebullition sensors for long-term (>1 year) in-situ measurements of CH4 flux.

ii)             Investigate biogeochemical controls on CH4 across a water body size continuum.

iii)            Utilise remote sensing techniques to upscale findings to regional scale.

This project will adopt a range of multidisciplinary techniques to establish rates, characteristics and drivers of CH4 efflux. Utilising a range of sensors and analytical methods the findings will allow a full carbon cycle accounting and enable a detailed understanding of the biogeochemical drivers to be established. Specifically, this project will hinge on the following key research approaches:

i) Long-term high- and medium-resolution gas flux measurements:

Utilising automated high-resolution sensors, alongside lower-resolution manual sampling, monitoring of gas fluxes will be performed across a range of different water body types and sizes.

ii) Characterising water chemistry & whole system carbon accounting:

Utilising in-situ sensors (for water chemistry) and the Glasgow carbon labs analytical suite, all facets of the aquatic carbon pool will be quantified allowing for biogeochemical controls to be elucidated both between and within sites. Discovered biogeochemical controls will be used for flux upscaling.

iii) Regional water body mapping & flux upscaling:

Accurate upscaling requires information on waterbody surface area, waterbody type and the distribution of productivity-related predictor variables (e.g. DOC and chlorophyll a.) (Deemer et al., 2021). High spatial resolution multispectral satellite imagery will be used to characterise waterbody type and surface area and predictive models developed for retrieving chlorophyll a from satellite observations. A time series analysis will characterise the inter-annual and intra-annual surface water dynamics.

  IAPETUS2’s postgraduate studentships are tenable for up to 3.5 years, depending on the doctoral research project the student is studying and provides the following package of financial support:

•           A tax-free maintenance grant set at the UK Research Council’s national rate, which in 2021/22 is £15,609.

•           Full payment of their tuition fees at the Home rate;

•           Access to extensive research support funding; &

•           Support for an external placement of up to six months.

Part-time award-holders are funded for seven years and receive a maintenance grant at 50% of the full-time rate.

  Eligibility

details can be found at https://www.iapetus2.ac.uk/how-to-apply/

IAPETUS2 is looking for candidates with the following qualities and backgrounds:

•           A first or 2:1 undergraduate degree, or have relevant comparable experience – we welcome applications from those with non-traditional routes to PhD study;

•           In addition, candidates may also hold or be completing a Masters degree in their area of proposed study or a related discipline; &

•           An outstanding academic pedigree and research potential, such as evidenced through the publication of articles, participation in academic conferences and other similar activities.

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

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

Start-date: September 2022

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