Paleolimnological Assessment of Environmental Changes Occurring on Pim Island
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Paleolimnological assessment of environmental changes occurring on Pim Island, Nunavut, High Arctic Canada by Alexandra Rouillard A thesis submitted to the Department of Biology in conformity with the requirements for the degree of Master of Science Queen’s University Kingston, Ontario, Canada December, 2010 Copyright © Alexandra Rouillard, 2010 ABSTRACT Despite the documented sensitivity of polar environments, long‐term monitoring data are especially sparse in these regions. Diatom‐based paleolimnology has contributed significantly to understanding the response of Arctic lakes to climate change, but most studies have been conducted in regions with relatively high lakewater buffering capacity. As such, Pim Island (Nunavut, Canada) is a region of limnological interest because, due to the local geology, its surface waters are of relatively lower pH and previous research suggests that such softwater lakes may be especially responsive to climate fluctuations and therefore provide the best paleoclimate records. This thesis has two separate but related chapters, as well as an exploratory study included in appendix. First, a novel approach using visible‐ near‐infrared spectroscopy (VNIRS) was used to infer lakewater dissolved organic carbon (DOC), from a 160‐lake calibration set from the Canadian Arctic. Historically sound and similar trends were reconstructed when compared against a Canadian diatom‐based DOC and Swedish VNIRS‐based total organic carbon (TOC) model on Arctic Holocene sediment records. Second, a diatom and spectroscopically‐based multi‐proxy approach was utilized on Holocene sedimentary records from two lakes on Pim Island to assess long‐term environmental change from this region. Benthic and epiphytic diatom taxa dominated the pre‐19th century assemblages, although marked shifts in dominant species were recorded during the mid‐Holocene. The mid‐Holocene diatom assemblages underwent an abrupt ecological shift from alkaliphilous Fragilaria sensu lato to slightly acidophilous Achnanthes and Navicula. The post‐19th century was characterized by an increase in the planktonic species (Cyclotella radiosa), indicating marked lakeice reductions. Third, the limnological properties and modern diatom assemblages of ponds and lakes surveyed from 1979 to 2009 on Pim Island were examined as part of an exploratory study. The ponds and lakes displayed typical characteristics observed in high Arctic lacustrine environments (i.e. ii oligotrophic, very dilute) but with overall relatively low alkalinity. Poorly‐buffered sites had diatom assemblages that were distinct from well‐buffered lakes elsewhere in the High Arctic. Our findings contribute to an improved understanding of the interactions between local environments and limnological changes, and also provide insight on the biological responses of lakes to Holocene environmental change and allow us to compare responses to those in more alkaline sites. iii COAUTHORSHIP I was the lead author for the two publication‐format chapters (Chapter 2 and Chapter 3) as well as the exploratory study presented in Appendix A. My M.Sc. supervisors, John P. Smol and Marianne S.V. Douglas, were co‐authors on all the manuscripts. In Chapter 2, co‐authors other than my M.Sc. supervisors included P. Rosén, who co‐supervised me during a 3‐months internship I completed at Umeå University, Sweden, where I completed the work on the VNIRS model development. P. Rosén also provided sediments from Seukokjaure for model testing. R. Pienitz provided surface sediment samples from Bylot Island, and reviewed the manuscript. Chapter 2 has been submitted to Journal of Paleolimnology. In Chapter 3, N. Michelutti was an additional co‐author on the manuscript, and took part in the study design, interpretations and reviewing process. iv ACKNOWLEDGEMENTS I thank John P. Smol, who trusted and supported me, and allowed me to take opportunities to expand my horizons. Also I need to thank him for being such an inspiration by doing important things and contributing to the international public debate. By making me work on and actually at Pim Island, John helped realize a dear dream to me, which was to experience the vastness of the extraordinary Arctic landscapes and see for myself how life can still thrive in such extreme environments. I want also to thank Marianne S.V. Douglas for her encouragement and support during this process. Peter Rosén, my Swedish supervisor, who has been supportive from the beginning to my VNIRS project. Weston Blake Jr. for providing the core material for my thesis, for his companionship in the high Arctic and his kindness, for sharing his knowledge on Pim Island and more. Reinhard Pienitz for his encouragement and reviews. Thanks to the members of my supervisory committee Brian F. Cumming and Scott Lamoureux for providing me with insightful comments. I would like to specifically thank Neal Michelutti for his guidance and support until the very end, Kathleen Rühland for being "un puit de savoir" on diatom taxonomy and pretty much everything else. Of course, I thank all of he PEARLites for the support and the good cheer. My time at PEARL would not have been the same without Chris Grooms and John Glew, who were patient enough to handle my multiple requests. My housemate, labmate and dear friend Katherine Griffiths, who supported my ups and downs until the very end throughout this process, for the laughs, and for being such a formidable person. Also, I would like to thank: Christian Bigler and Richard Bindler, in Sweden, for introducing me to paleolimnology and later hosting me in their offices during my stay at Umeå University; Alexandre Poulain who introduced me to Arctic research; the 2009 Arctic Geoecology students, for being my modelling partners during those long and dark fall days at the Abisko Research Station; Annika Holmgren who shared her laughs expertise on VNIRS; Johan v Rydberg and Sophia Hansson, who willingly shared their office space and "fika" breaks with me; the Cape Herschel 2009 field crew, for sharing Pim Island and polar bears adventures. Alexander Wolfe for French cheer and helpful comments; and my friends here and overseas for listening and moral support. Je tiens aussi à remercier (en français) ma famille, tout particulièrement Jean‐Paul, mon parrain et ma marraine, ma grand‐mère, Georges et Denis, de m'avoir encouragée jusqu'à en arriver là, et d'avoir accepté sans broncher que j'habite si loin si souvent. Par dessus tout, je dis un gros "Merci" à ma maman pour m'avoir fourni les outils nécessaires à la réalisations de mes rêves et pour avoir toujours été là. Est‐ce que "Merci" c'est assez pour exprimer tout ça? Finally Peter, for being my companion, my anchoring stone; for everything and more to come. vi TABLE OF CONTENTS ABSTRACT ii COAUTORSHIP iv ACKNOWLEDGEMENTS v TABLE OF CONTENTS vii LIST OF TABLES ix LIST OF FIGURES x LIST OF ABBREVIATIONS xi CHAPTER 1: General Introduction and Literature Review 1 Introduction 1 Paleolimnology in the high Arctic 3 Indicators 5 Thesis Format 9 References 11 CHAPTER 2: Development and application of a model for inferring lake water dissolved organic carbon (DOC) from visiblenearinfrared spectroscopy (VNIRS) measures in lake sediment 16 Abstract 17 Introduction 18 Materials and methods 20 Results and Discussion 29 Conclusions 36 Acknowledgements 37 References 38 CHAPTER 3: The response of poorlybuffered High Arctic lakes to climatic fluctuations over the Holocene 51 Abstract 52 Introduction 53 Sites Description 55 Methods 58 Results 64 Discussion 76 Summary 85 Acknowledgements 87 References 88 CHAPTER 4: General Discussion 106 Tool development for high Arctic paleoenvironmental studies 106 Local influence to Holocene climate response from poorly‐buffered lakes 107 References 110 vii CHAPTER 5: Summary and Conclusions 111 APPENDICES 113 Appendix A 114 Appendix B 141 Appendix C 156 Appendix D 157 Appendix E 164 Appendix F 165 Appendix G 171 Appendix H 179 Appendix I 191 viii LIST OF TABLES Chapter 2 Table 2.1. Canadian Arctic lakes calibration set (CACS) regions. 43 Table 2.2. Meteorological data (1990‐2009) of the CACS. 44 Table 2.3. Select water chemistry variables for the 160 CACS lakes. 45 Chapter 3 Table 3.1. Select geographical, topographical and limnological properties from West Lake and 260 m Lake. 95 Table 3.2. Core descriptions for West Lake (a) and 260 m (b) Lake. 96 Table 3.3. Radiocarbon ages from West and 260 m Lake cores. 97 Appendix A Table A.1. Available geographical, topographical and morphological properties, ice cover at sampling and collection periods for 3 lakes and 5 ponds studied on Pim Island. 135 Table A.2. Summer water chemistry of lakes and ponds on Pim Island. 136 ix LIST OF FIGURES Chapter 2 Fig. 2.1: Map of the Canadian Arctic Calibration Lakes Set (CACS). 46 Fig. 2.2: Observed lake water dissolved organic carbon (DOC) versus near‐infrared spectroscopy (VNIRS)‐predicted lake water DOC from the CACS. 47 Fig. 2.3: Reconstructions of past lake water DOC from Slipper Lake (NWT, Canada). 48 Fig. 2.4: Reconstruction of past lake water DOC and TOC (mg·L‐1) from Seukokjaure (Sweden). 49 Fig. 2.5: Principal component analysis (PCA) of the VNIRS signatures from the Canadian 160 lakes and the Swedish 99 lakes surface sediment training sets. 50 Chapter 3 Fig. 3.1: Topographic map of Pim Island and the Cape Herschel. 98 Fig. 3.2: Relationship between total 210Pb activity for West Lake and 260 m Lake Holocene cores. 99 Fig. 3.3: Linear regression‐based age‐depth models for West Lake and 260 m Lake. 100 Fig. 3.4: Holocene diatom records stratigraphies for West Lake and 260 m Lake. 101 Fig. 3.5: West and 260 m lakes Holocene records of the diatom downcore assemblages,the first 2 DCA samples score axes, diatom‐inferred pH, sedimentary Chla and VNIRS‐ inferred DOC (VNIRS‐DOC). 103 Fig. 3.6: Principal component analysis (PCA) of the VNIRS signatures from the 160 Canadian Arctic surface sediment calibration set.