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

Supervisor: Andrew Tanentzap (Plant Sciences)  

Reference Code: B409

Importance of the area of research:

The perennially frozen landscapes of the Arctic store at least twice as much carbon as the atmosphere, acting as a vital brake on global climate change, but these ecosystems are increasingly vulnerable to warming temperatures (Schurr et al. 2015).  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 (Wik et al. 2016).

Project summary:

The aim of this studentship is to test whether permafrost thawing influences the productivity and resource use of bacterioplankton in Arctic lakes.  The first part of the project will test how the productivity of algal and bacterial communities varies with permafrost coverage during the growing season, accounting for variation among sites in water chemistry and watershed characteristics.  Field data will be collected by repeatedly surveying ca. 30 lakes spanning a gradient of continuous-discontinuous-sporadic permafrost across northern Canada.  The second part of the project will track the contribution of CH4 to bacterial production (Grey 2016).

What the student will do:

The student 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 involving paddling to the middle of small lakes and collecting water samples that will be analysed for bacterial productivity using radiolabelled incubations.  Algal productivity will be monitored in situ with a chlorophyll fluorometer.  The student will then use statistical models to test how permafrost type and lake characteristics influence productivity.  Concurrent with their field surveys, the student will assess methanotrophy using 13CH4 enrichment experiments and relate this to the expression of genes involved in methanogenesis and the broader permafrost gradient.

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

  • Schuur, E.A.G. et al. 2015. Climate change and the permafrost carbon feedback. Nature, vol 520, pp.171-179. DOI:10.1038/nature14338
  • Wik, M. et al. 2016. Climate-sensitive northern lakes and ponds are critical components of methane release. Nature Geoscience, vol 9, pp.99-105. DOI:10.1038/ngeo2578
  • Grey, J. 2016. The incredible lightness of being methane-fuelled: stable isotopes reveal alternative energy pathways in aquatic ecosystems and beyond. Frontiers in Ecology and Evolution, vol 11, pp.8. DOI:10.3389/fevo.2016.00008

Follow this link to find out about applying for this project.