Sam Cottingham

Project: Susceptibility of Arctic permafrost carbon to microbial respiration

Climate warming in the arctic is thawing deposits of permanently frozen soils termed permafrost which are estimated to contain twice the amount of carbon as is presently in the atmosphere. A considerable uncertainty is how losses of thawed soil organic carbon will impact upon freshwater systems such as streams, particularly how microbial communities, which act to degrade and respire this carbon to the atmosphere will respond to changing inputs. This project focuses upon the composition of dissolved organic matter (DOM) across a rapidly thawing sub-arctic landscape in northern Sweden and aims to assess the availability to microbial communities. To do this a range of novel analytical techniques are applied to measure DOM composition, microbial function and community composition. The results will be used to advance understanding of impacts upon aquatic biogeochemistry with continued permafrost thaw and induced changes to land-cover.

Specific research aims are:

1. Determine the variability of DOM composition in sub-arctic streams draining land-cover types indicative of permafrost thaw state and long-term ecosystem transition.

2. Establish patterns of microbial nutrient limitation in streams with seasonally increasing active-layer depths in relation to nutrient availability and DOM composition.

3. Experimentally investigate the role of DOM composition and nutrient availability in explaining the established patterns of microbial function.

Supervisor:
Dr Paul Mann