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Tanentzap Group: Thawing Arctic: productivity and sources of carbon cycling in small lakes

NERC / UF / OTHER

Supervisor: Andrew Tanentzap (Plant Sciences)
Co-Supervisor: Dr David Olefeldt, University of Alberta https://caws.ualberta.ca/

Importance of research:

The perennially frozen landscapes of the Arctic are a vital brake on global climate change but are changing faster than anywhere else on Earth (Schurr et al. 2015). Within the northern permafrost region, peatlands alone store about one-third of all the carbon (C) in the atmosphere (Hugelius et al. 2020). While these C stocks have accumulated over centuries and millennia, as frozen and waterlogged soils have slowed microbial decomposition, they are now threatened by rapid warming. One outcome of accelerated thaw is an increase in the area of small lakes in the continuous permafrost zone, which can act both as a positive feedback to climate warming and fuel chemosynthetic primary production by releasing CO2 and CH4 from previously frozen organic matter. By contrast, changes in hydrology in zones of discontinuous permafrost may change the productivity of thermokarst lakes and ponds in ways that are less well understood. The fate of CH4 in thermokarst lakes is particularly important to trace as it is at least 25-times more potent a greenhouse gas than CO2 and exceptionally abundant in Arctic permafrost ecosystems.

Project summary:

The aim of this studentship is to test how permafrost thaw influences the productivity and resource use of bacterioplankton in Arctic freshwaters. In the first part of this project, you will measure the biomass and productivity of algal and bacterial communities during the growing season in continuous, discontinuous, and sporadic permafrost in northern Canada. This gradient acts as a space-for-time substitution for future climate change. You will also quantify how much millennial-aged C is incorporated into the aquatic food web vs lost downstream using isotopic tracers and mass balance calculation. The second part of the project will track the contribution of CH4 to bacterioplankton production and scale-up these estimates using geospatial analyses to revise regional C budgets. Finally, you may perform an experiment to test how changes to soil C export influence aquatic C cycling.

What will the student do?

You will help design a multi-year field study and collect all the associated data, working in remote locations for long periods of time with a team of Canadian collaborators. Data collection will involve paddling to the middle of small lakes and/or visiting remote streams where you will collect water samples that will be analysed for bacterial and algal productivity using bottle incubations and radiolabels. You will also use isotopic tracers (e.g. 13C and 14C; Ishikawa et al. 2014) and mass balance calculations to estimate the contribution of different C sources towards algal biomass and how these vary with landscape context, e.g. permafrost thaw and hydrology. Concurrent with the field surveys, you will assess methanotrophy by developing 13-CH4 enrichment experiments, potentially alongside soil warming/drainage experiments.

Training to be provided:

You will be trained in carrying out field work (including limnological sampling), experimental design, and statistical modelling (including computer programming). Training in lab-based molecular biology techniques will also be provided, but some skills in DNA/RNA extraction, library construction and qPCR are advantageous.

References:

  • Hugelius, G., Loisel, J., Chadburn, S. et al. 2020. Large stocks of peatland carbon and nitrogen are vulnerable to permafrost thaw. PNAS, vol. 117, pp.20438-20446. https://doi.org/10.1073/pnas.1916387117
  • Schuur, E.A.G., McGuire A.D., Schädel C. et al. 2015. Climate change and the permafrost carbon feedback. Nature, vol 520, pp.171-179. https://doi.org/10.1038/nature14338
  • Ishikawa, N.F., Uchida, M., Shibata, Y. & Tayasu, I. (2014). Carbon storage reservoirs in watersheds support stream food webs via periphyton production. Ecology, vol. 95, pp.1264–1271. https://doi.org/10.1890/13-0976.1

For details on how to apply to the Cambridge NERC Doctoral Training Partnerships see https://nercdtp.esc.cam.ac.uk/ 

 

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