Seasonal microbial ecology and biogeochemistry of snow during spring and summer melt in Svalbard

Abstract

Our understanding of snowpack ecosystems is primarily derived from studies based on snow-on-soil ecosystems or from snow upon aquatic ecosystems. However, most of the world’s persistent snow cover lies on glaciers and ice sheets. This means that greater research attention needs to be directed to the study of glacial snow covers. Moreover, with rising temperatures, snowpacks are getting wetter and less persistent globally which can potentially give rise to more biologically productive snowpacks, where they remain. In this context, the present study set out to determine the linkage between thermal evolution of a snowpack and seasonal microbial ecology of snow during the melt season. A comprehensive field campaign involved the collection of snow, superimposed ice and glacial ice samples at seven different sites monthly for four months (spring to summer) on a High Arctic ice cap (Foxfonna, Svalbard). A mass balance framework was adopted to highlight the linkages between nutrients, microbial biomass and the changing physical conditions of a melting snowpack, for the first time. Next, the experimental data showed that the glacial snowpack microbial ecosystem was net-heterotrophic and the taxa identified were typical of Arctic snowpacks. Nutrients acquired from winter atmospheric bulk deposition for the bacterial heterotrophic communities within the snowpack were supplemented by a major input from dust fertilization and weathering processes. Primary production did not respond to this input due to an absence of autotrophs in the snowpack. The bacterial production on the ice cap was characterised by the proliferation of ‘dead cells’ and a pseudolysogeny hypothesis was invoked to explain this surprising result. These results have wide-ranging implications in terms of enhanced primary and bacterial production in downstream ecosystems, for snowpacks are well-connected to both terrestrial and marine systems. Thus, the findings presented in this thesis significantly enhance our understanding of glacial snowpack microbial ecosystems.

Date of Award	2021
Original language	English
Awarding Institution	University of Sheffield
Sponsors	COMMONWEALTH SCHOLARSHIP COMM.
Supervisor	Andrew J. Hodson (Supervisor)