Microbial succession from ice to vegetated soils in response to glacial retreat

Glaciers in the Northern Hemisphere are retreating and their forefields present a unique opportunity to investigate the initial phases of soil  weathering/formation and microbial succession. For the Greenland ice sheet, for instance, it is estimated that the permanent frozen surface area could diminish by up to 60% by 2100. As the proportion of deglaciated areas increases, the changes in microbial communities and associated biogeochemical processes will impact the physical and biogeochemical conditions in glacial runoff, with implications for coastal water productivity. Such new deglaciated terrains are also very important for understanding global biogeochemical cycles and atmospheric CO2 concentrations, since this can lead to enhanced rates of dissolution over timescales of >100 kyrs and that silicate dissolution rates may be three times higher compared with more temperate soils. Given the importance of microbial processes in soil weathering and organic matter formation, clearly, the nature of the microbial biogeochemical transformations of recently exposed glacial soils is of great interest to the broader Earth system science community.

Our proposal aims to employ a function-based metagenomic approach, in combination with geochemical, and microbial activity and diversity measurements in soils, to generate new and uniquely integrated datasets of functional and genetic diversity of representative terrestrial Arctic habitats recently exposed after glacial retreat.

The major deliverable of this project will be a unique database of quantifiable metabolic pathways and biogeochemical processes in Arctic soils extending from newly exposed soils after glacial retreat to well developed vegetated soils. The chronosequence approach will be directly related to predictions in biogeochemical changes during glacial retreat in a warming climate scenario.

Our prime objectives are:

1)  Determine the phylogenetic and functional composition of microbial assemblages present across chronosequences of recently exposed soils in Svalbard and Greenland;

2)  Understand the horizontal and vertical distribution of inter-related metabolic processes within these chronosequences (e.g., C dynamics, N fixation, S and P assimilation, and anoxic metabolism in relation to physical and chemical characteristics (e.g., redox, T, DOM/DOC etc)

3)  Investigate the relationships between phylogenetic and metabolic composition and the variations in mineralogical and key biogeochemical processes;

The project will employ a PDRA in Bristol who will focus primarily on the phylogenetics and functional composition of the microbial assemblages and their impact onto biogeochemical processes.

There are also two tied studentships – one of which (based in Bristol) is aimed at developing a numerical model of soil formation which incorporates processes of microbial succession.

The PhD project based in The Cohen Group in Leeds has the main objective to:

(a)  develop a combined field and laboratory framework for the understanding of changes in key geochemical and mineralogical parameters in glacial forefields

(b)  quantify how leads to the development of pristine soils.

Further reading:

[1] Parkinson CL 2006. Earth's cryosphere: Current state and recent changes. In Annual Review of Environment and Resources 33-60.

[2] Derry L (2009) Geochemistry: A glacial hangover; Nature 458, 417-418 and Vance D et al 2009. Variable Quaternary chemical weathering fluxes and imbalances in marine geochemical budgets Nature 458:493-496

[3]Bernasconi S et al (2008) Weathering, soil formation and initial ecosystem evolution on a glacier forefield: a case study from the Damma Glacier, Switzerland Min Mag 72: 19-22