This project is one of a number that are in competition for funding from the NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP). The NERC GW4+ DTP involves the four research-intensive universities across the South West – Bath, Bristol, Cardiff and Exeter – and six Research Organisation partners. For further details about the programme please see www.bristol.ac.uk/gw4plusdtp

Studentships will be awarded on the basis of merit and will commence in September 2014. For eligible students the award will cover UK/EU tuition fees and an annual stipend (in 2013/14 this was £13,726 for full-time students, pro rata for part-time students) for three and a half years.

Supervisors:
Dr Iain Hartley, College of Life and Environmental Sciences, University of Exeter, Exeter
Dr Gabriel Yvon-Durocher, College of Life and Environmental Sciences, University of Exeter, Environmental Sustainability Institute, Penryn
Dr Tim Smyth, Plymouth Marine Laboratory, Plymouth

Project description:  Determining how microbial respiration responds to temperature is essential for predicting how terrestrial and marine ecosystems will respond to 21st century climate change. For example, warming-induced carbon release from soils has been identified as one of the most important positive feedbacks to climate change. However, short- and long-term responses of microbial respiration to warming have been shown to differ dramatically, raising the potential for acclimation within individuals, adaptation within populations, and changes in microbial community structure to modify the direct effects of temperature on respiratory physiology. For soil and marine systems, a wide range of effects have been observed with microbial community responses being shown to both reduce and increase the direct impacts of warming on respiration. However, determining why such contrasting results have been observed has been challenging and developing a unifying theory to explain the responses remains elusive.

Models from metabolic theory, developed by Yvon-Durocher, predict a direct coupling between the size distribution of organisms and community metabolic flux and have the potential to yield significant insight into mechanistic basis of the coupling between microbial community structure and system respiration. These models have the potential to significantly enhance the capacity of process-based biogeochemistry models to predict the response of community respiration warming – a factor that currently remains highly uncertain. However, they have not currently been adequately tested in a range of environments. This project will make high-resolution, detailed measurements of the microbial size distribution and rates of community respiration under a range of warming scenarios in experimental mesocosms that represent both soil and marine microbial communities. Soils are highly heterogeneous environments, with factors such as chemical and physical protection, and moisture contents affecting the availability of organic matter to microbes. Combining soil-based experiments with studies of heterotrophic activity in an aqueous medium represents a potentially powerful approach for developing fundamental understanding. This work will yield significant insight into the similarities and differences in the mechanisms that link community structure and ecosystem functioning across aquatic and terrestrial environments.

The knowledge and understanding developed will be directly applicable to modelling terrestrial and marine feedbacks to climate change. For example, it would be possible to scale up the findings from the marine work to the global level using satellite derived products such as temperature and ocean colour. This could uniquely give a broad overview of the metabolic status of the global ocean, which is currently a contentious issue.

Closing date: 10th January 2014