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

When glaciers retreat, their forefields present a unique opportunity to investigate the initial phases of soil formation and microbial succession. As the ice retreats leaving space for microbial and plant colonisation, some studies show evidence of an increase in a variety of microbial proxies, such as nitrogen fixation, microbial enzymatic activity and diversity, in relation to years of exposure until certain soil stability is reached. Surprisingly, very little is known regarding the genetic and functional diversity of microbes in Arctic habitats. The composition and the metabolic potential of the entire microbial population can be explored by isolating and characterising their genetic material recovered directly from the environment using a metagenomic approach. Each sample of a soil habitat analysed represents a snapshot of the complex mixture of different microbial types and some types will be much more abundant than others. For instance, we predict in this project that genes associated with phototrophic C and N fixation and aerobic C metabolism will be predominant at the initial stages of succession in soil after glacial retreat, while deeper soil samples will provide conditions for anaerobic C and N metabolism to develop, include the production and consumption methane, which is a very powerful greenhouse gas. The metagenomic approach can be further linked to rates of metabolism and geochemical characteristics of soils, many of those factors have strong feedbacks with each other. There have been few integrated studies which link microbial diversity to ecosystem function and the biogeochemical cycling of key elements (C, N, Fe). This proposal aims to employ such integrated approach to generate new and uniquely datasets of genetic and functional diversity of representative terrestrial Arctic habitats. The project will instigate a step jump in our understanding of metabolic pathways of terrestrial Arctic habitats to improve biogeochemical models and quantification of the full metabolic package during successional events in soils after glacial retreat. The forefields of 2 glaciers (one in Svalbard and one in Greenland, which represent one small polar system and one major ice sheet, respectively) will be chosen for this project because they provide a range of forefield habitats of different sizes, locations, vegetation and availability of water surrounding the system. Samples for the metagenomic analyses will be taken from representative soils representing different ages of exposure after glacial retreat. We aim to generate several orders of magnitude more primary sequence data than existing metagenome pipelines were originally designed to deal with. This sampling strategy will give us a high-resolution picture of the microbial genetic and metabolic diversity associated with key elements (e.g., C, N, Fe) of glacial forefield habitats, also allowing us to PREDICT changes in metabolic pathways and biogeochemical cycles in response to glacial retreat. The project will instigate a step jump in our understanding of the biodiversity of glacial Arctic terrestrial habitats and provide a database that may be used to interpret data recovered during future. This will ultimately give us valuable insights in relation to the potential for life in other icy planets and moons and during the so called Snowball Earth. Data generated in this proposal can be incorporated into models of carbon, nitrogen, iron and sulphur cycling.

Our main objectives are 1) to create unique database of Arctic soil metagenomes that will be publically available towards the end of the project and 2) to produce a short documentary of Arctic research aimed to primary school pupils.

The database will contain a friendly environment to explore the sequences obtained in this project with links to similar projects. In addition to submitting sequence data to the SRA at EMBL, we will add further contextual value by developing customized on-line data interrogation tools to enable researchers to fully mine the rich dataset developed. Further, we will also create a section in the database that links the genetic and metabolic data with modelling of successional events within newly exposed soils after glacial retreat. A further section will contain microscopic images of the autotrophic composition of our samples and another will be addressed to school age children (secondary school). This section will contain stories and descriptions of the main microbial processes in Arctic soils and their significance for climate and the biogeochemistry of these habitats. The Co-PI in the project, Gary Barker, has a strong track record of developing such databases.

We will also create an educational video that engages and entertains primary school to reveal a great deal about how mankind is affecting our environment. We will take advantage from a wealthy amount of footage from our previous project aimed to A-level pupils to add value to the video produced by this project. A geography/science school consultant will also participate in this project to ensure the new film is in line with the national curriculum so it gets as wide a viewing as possible.