Articles | Volume 13, issue 19
Biogeosciences, 13, 5677–5696, 2016
Biogeosciences, 13, 5677–5696, 2016

Research article 13 Oct 2016

Research article | 13 Oct 2016

Microbial dynamics in a High Arctic glacier forefield: a combined field, laboratory, and modelling approach

James A. Bradley1,2,6, Sandra Arndt2, Marie Šabacká1, Liane G. Benning3,4, Gary L. Barker5, Joshua J. Blacker3, Marian L. Yallop5, Katherine E. Wright1, Christopher M. Bellas1, Jonathan Telling7, Martyn Tranter1, and Alexandre M. Anesio1 James A. Bradley et al.
  • 1Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, BS8 1SS, UK
  • 2BRIDGE, School of Geographical Sciences, University of Bristol, BS8 1SS, UK
  • 3School of Earth and Environment, University of Leeds, LS2 9JT, UK
  • 4GFZ, German Research Centre for Geosciences, 14473 Potsdam, Germany
  • 5School of Biological Sciences, University of Bristol, BS8 1SS, UK
  • 6Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA
  • 7School of Civil Engineering and Geosciences, Newcastle University, UK

Abstract. Modelling the development of soils in glacier forefields is necessary in order to assess how microbial and geochemical processes interact and shape soil development in response to glacier retreat. Furthermore, such models can help us predict microbial growth and the fate of Arctic soils in an increasingly ice-free future. Here, for the first time, we combined field sampling with laboratory analyses and numerical modelling to investigate microbial community dynamics in oligotrophic proglacial soils in Svalbard. We measured low bacterial growth rates and growth efficiencies (relative to estimates from Alpine glacier forefields) and high sensitivity of bacterial growth rates to soil temperature (relative to temperate soils). We used these laboratory measurements to inform parameter values in a new numerical model and significantly refined predictions of microbial and biogeochemical dynamics of soil development over a period of roughly 120 years. The model predicted the observed accumulation of autotrophic and heterotrophic biomass. Genomic data indicated that initial microbial communities were dominated by bacteria derived from the glacial environment, whereas older soils hosted a mixed community of autotrophic and heterotrophic bacteria. This finding was simulated by the numerical model, which showed that active microbial communities play key roles in fixing and recycling carbon and nutrients. We also demonstrated the role of allochthonous carbon and microbial necromass in sustaining a pool of organic material, despite high heterotrophic activity in older soils. This combined field, laboratory, and modelling approach demonstrates the value of integrated model–data studies to understand and quantify the functioning of the microbial community in an emerging High Arctic soil ecosystem.

Short summary
Soil development following glacier retreat was characterized using a novel integrated field, laboratory and modelling approach in Svalbard. We found community shifts in bacteria, which were responsible for driving cycles in carbon and nutrients. Allochthonous inputs were also important in sustaining bacterial production. This study shows how an integrated model–data approach can improve understanding and obtain a more holistic picture of soil development in an increasingly ice-free future world.
Final-revised paper