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B337: Tracing the fate of terrestrial-derived carbon in aquatic food webs (Lead Supervisor: Andrew Tanentzap, Plant Sciences)

Supervisor: Andrew Tanentzap (Plant Sciences)

Importance of the area of research:

Terrestrial-derived carbon exerts a major influence over the biogeochemical cycling and food webs of aquatic ecosystems, especially in the small nutrient-poor lakes that dominate the planet.  Consequently, nearly 70% of the biomass of aquatic organisms can be derived from terrestrial origins (Tanentzap et al. 2014).  However despite this observation, a major controversy is whether terrestrial-derived organic matter (tOM) can support high levels of production by aquatic organisms given that it is often nutritionally poor material (Kelly et al. 2014).  Predicting the conditions when tOM is important for supporting aquatic production will improve watershed planning by better coupling land and water management.

Project summary:

The aims of this studentship are to trace the movement of terrestrial carbon in freshwater lakes and then test how autotrophic and bacterial production vary with the quantity and quality of tOM.  The first part of this project will involve isotopically labelling leaves in the streams of 5 boreal catchments.  We will use these leaves to test how their incorporation into sediment, greenhouse gases, and primary consumers from headwaters into the pelagic zone vary with geomorphology and physical limnology of the different sites.  For the second part of this project, the student will partake in a multi-lake experiment based in Canada that provides controlled gradients of tOM along which to measure primary production.

What the student will:

The student will design and execute the tracer study.  This will involve growing birch (Betula) trees in a glasshouse and regularly fumigating plants with 13C.  Leaves from these plants will be deployed into the different sites during spring runoff.  The student will then collect sediment cores, water samples, and net zooplankton at different locations in each catchment at the end of the growing season.  Samples will be dried and encapsulated for stable isotope analyses.  Physical characteristics of each site, such as flow rate, residence time, water colour, will also be recorded and the geomorphology of sites characterised from GIS databases.  For the tOM experiment, the student will travel to the study site in Canada and collect weekly water samples.  Autotrophic and bacterial production will be measured in the lab using standard incubation approaches (Ask et al. 2009).

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:

Ask, J., Karlsson, J., Persson, L., Ask, P., Byström, P. & Jansson, M. 2009. Terrestrial organic matter and light penetration: Effects on bacterial and primary production in lakes. Limnology and Oceanography, vol. 54, pp.2034-2040.

Kelly, P.T., Solomon, C.T., Weidel, B. & Jones, S.E. 2014. Terrestrial carbon, is a resource, but not a subsidy, for lake zooplankton. Ecology, vol. 95, pp.1236-1242.

Tanentzap, A.J., Szkokan-Emilson, E.J., Kielstra, B.W., Arts, M.T., Yan, N.D. & Gunn, J.M. 2014. Forests fuel fish growth in freshwater deltas. Nature Communications, vol. 5, 4077.

Follow this link to find out about applying for this project

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