The role of land-ocean fluxes in UK and Malaysian carbon budgets

Soil organic carbon (C) is a large (1500-2400 GT) pool of rapidly exchangeable carbon, concentrated in high northern or tropical latitudes, which is lost to inland waters at a rate (1.7 Gt C yr-1) comparable to the oceanic or terrestrial uptake of anthropogenically remobilised carbon from the atmosphere. Riverine organic C concentrations are increasing significantly across much of western Europe and cryosoils are beginning to thaw suggesting that this part of the earth system is no longer in steady state. Further, changes in land use patterns in SE Asia are beginning to mobilise relict organic C into rivers and estuaries. Unfortunately our current state of knowledge regarding the fate of this material as it enters coastal and estuarie waters is poor. According to the IPCC ‘“many of the key processes relevant to decomposition of [terrigenous] C are missing in models, particularly for C stored in boreal and tropical peatlands, despite their vulnerability to warming and land use change”. This project will rectify our uncertainty regarding the fate of soil organic C as it enters the estuarine environment using a combination of field surveys and experiments, linking to a series of funded NERC projects across the UK and the world (www.locate.ac.uk).

You will address the principal aims of the project by evaluating the rates of, and controls over, terrestrial organic C loss in the estuarine environment in selected UK and foreign systems. A central fieldwork location will be the Beaulieu estuary which drains the New Forest, the largest area of semi-natural landscape and forest in Southern England, and which serves as a model for pristine N European systems. Initial work will focus on estimating loss and transformation processes using fluorescence and absorption spectra synthesized using the PARAFAC method, and the associated release of dissolved inorganic C. Further work will focus on understanding the key processes involved in organic C loss including priming, sedimentation and photolysis, and the input of groundwater to the system using radium isotopes. The relative importance of these processes is likely to vary in both space and time and be related to substrate, light and nutrient availability. Similar observations will be made in Malaysia with Mujahatid and Mueller via sampling river/ estuarine systems in Sarawak, Malaysian Borneo draining both relict peatland swamp forests and managed landscapes.

The SPITFIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be hosted within the Ocean Biogeochemistry and Ecosystems group at the National Oceanography, an internationally recognized centre of excellence in earth system science, and link to our international partners in Kuching, Sarawak. These latter partners will provide the opportunity to sample very high carbon estuaries which drain tropical peatland swamp forests, some of the most carbon rich systems on earth. Further fieldwork may be possible in South Africa and the Falkland Islands to evaluate the functioning of semipristine Southern Hemisphere systems. Specific training will include (i) PARAFAC analysis on water and sediment samples; (ii) experimental work to evaluate respiration, priming and photolysis and (iii) Radium analyses to evaluate groundwater inputs.