Hydrological Controls on the Biogeochemistry of Polar Glacier Ice and its Meltwater by Ashley Dubnick A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Earth and Atmospheric Sciences University of Alberta © Ashley Dubnick, 2018 Abstract Ice masses in the Antarctic, Greenland, and Canadian Arctic cover approximately 10% of the Earth’s surface, contain approximately 70% of the Earth’s freshwater, and are the top contributors to eustatic sea level rise. In recent years, these polar glacier systems have experienced significant increases in mass loss and melt rates, and the quantity of melt in these regions is expected to increase further under a warming climate. Existing research indicates that the physical, chemical, and microbial characteristics of these ice masses and the meltwater they produce are often distinct from those of other natural water sources. Their characteristics also show high temporal and spatial variability that may result from the combined presence of distinct and variable biogeochemical environments, particularly on the glacier surface and near the bed, and the strong variations in hydrological dynamics that often occur in glacial systems. This study examines glacier ice and meltwater from the Antarctic, Greenland, and Canadian Arctic to (1) investigate the variability in microbial assemblages and nutrient species/concentrations in the various biogeochemical environments that exist within and between polar glacier systems, and (2) evaluate how glacier hydrology influences the development and export of microbes and nutrients from these systems. Results of this study indicate that distinct biogeochemical environments exist in glacial systems, that they can function as sources and/or sinks for specific nutrients and microbes, and that the nutrients and microbes exported in glacial meltwater can vary according to the meltwater sources, flow paths, and residence times within the glacial system. Consequently, the biogeochemical characteristics of glacier ice and meltwater can differ between glaciers with different features, thermal regimes and/or hydrological systems, can change over the course of the melt season as the hydrological system within a glacier evolves, and can show different seasonal patterns for specific microbiological and nutrient parameters. ii Preface A version of Chapter 2 has been published [Dubnick et al., 2017b]. I was responsible for field measurements and sample collection, data analysis and manuscript composition. J. Wadham and J. Orwin collaborated on the study design and field work and all authors (J. Wadham, M. Tranter, M. Sharp, J. Orwin, J. Barker, E. Bagshaw and S. Fitzsimons) contributed to manuscript edits. A version of Chapter 3 has also been published [Dubnick et al., 2017a]. I was responsible for study design, data collection and analyses and manuscript composition. J. Hawkings and A. Beaton collaborated on the study design, hydrology/chemistry fieldwork, and chemical analyses and S. Kazemi completed DNA extractions and contributed to microbial data analyses. S. Kazemi, M. Sharp, J. Wadham, J. Hawkings, A. Beaton, and B. Lanoil contributed to manuscript edits. Hydrology and chemistry field data were also published elsewhere [Hawkings et al., 2016]. Chapter 4 is unpublished work. I completed the study design, field work, sample processing, data analyses and manuscript composition. B. Danielson assisted with field work and sampling and A. Saidi-Mehrabad completed DNA extractions. M. Sharp, M. Bhatia and J. Barker contributed to manuscript edits. iii Table of Contents Abstract .............................................................................................................................. ii Preface ............................................................................................................................... iii Table of Contents ............................................................................................................. iv List of Tables .................................................................................................................. viii List of Figures ................................................................................................................... ix Chapter 1: Introduction ....................................................................................................1 1.1 Motivation ........................................................................................................... 1 1.2 Objectives and thesis outline .............................................................................. 3 1.3 Scientific background ......................................................................................... 4 Chapter 2: Trickle or treat: the dynamics of nutrient export from polar glaciers ....12 2.1 Abstract ............................................................................................................. 12 2.2 Introduction ....................................................................................................... 13 2.3 Methods............................................................................................................. 16 2.3.1 Study site ....................................................................................................... 16 2.3.2 Data collection .............................................................................................. 17 2.3.2.1 Discharge monitoring ............................................................................. 17 2.3.2.2 Meteorological monitoring ..................................................................... 18 2.3.2.3 Sampling................................................................................................. 18 2.3.3 Laboratory analyses ...................................................................................... 19 2.3.4 Data processing and statistical analyses ....................................................... 20 2.4 Results ............................................................................................................... 21 2.4.1 Hydrology and major ions ............................................................................ 21 iv 2.4.2 Dissolved inorganic nitrogen ........................................................................ 22 2.4.3 Dissolved inorganic phosphorus ................................................................... 23 2.4.4 Dissolved organic matter .............................................................................. 24 2.5 Discussion ......................................................................................................... 26 2.5.1 Nutrient sources and sinks along the flow path ............................................ 26 2.5.1.1 Supraglacial environments ..................................................................... 26 2.5.1.2 Ice-marginal environments ..................................................................... 27 2.5.1.3 Proglacial environments ......................................................................... 30 2.5.2 Trickle or Treat: hydrologically controlled nutrient dynamics ..................... 30 2.6 Conclusions ....................................................................................................... 35 2.7 Acknowledgements ........................................................................................... 36 Chapter 3: Hydrological controls on glacially exported microbial assemblages .......45 3.1 Abstract ............................................................................................................. 45 3.2 Introduction ....................................................................................................... 46 3.3 Methods............................................................................................................. 49 3.3.1 Field site ........................................................................................................ 49 3.3.2 Sample collection and processing ................................................................. 49 3.3.3 Chemical indices ........................................................................................... 51 3.3.4 Analytical procedures ................................................................................... 53 3.3.5 DNA sequence processing and statistical analyses ....................................... 55 3.4 Results ............................................................................................................... 57 3.4.1 Hydrology/hydrochemistry ........................................................................... 57 3.4.2 Microbiology................................................................................................. 58 v 3.5 Discussion ......................................................................................................... 60 3.5.1 Hydrological regime ..................................................................................... 60 3.5.2 First-order control on exported microbial assemblages: subglacial drainage 62 3.5.3 Second-order control on exported microbial assemblages: source water and subglacial residence time .............................................................................. 63 3.6 Conclusions ....................................................................................................... 64 3.7 Acknowledgements ..........................................................................................