MULTI-PROXY RECONSTRUCTIONS OF HOLOCENE ENVIRONMENTAL CHANGE AND CATCHMENT BIOGEOCHEMISTRY USING ALGAL PIGMENTS AND STABLE ISOTOPES PRESERVED IN LAKE SEDIMENT FROM BAFFIN ISLAND AND ICELAND by CHRISTOPHER ROTH FLORIAN B.A., University of Colorado, 2007 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirement for the degree of Doctor of Philosophy Department of Geological Sciences 2016 This thesis entitled: Multi-proxy reconstructions of Holocene environmental change and catchment biogeochemistry using algal pigments and stable isotopes preserved in lake sediment from Baffin Island and Iceland has been approved for the Department of Geological Sciences Gifford H. Miller Áslaug Geirsdóttir Date The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. ii Florian, Christopher Roth (Ph.D., Geological Sciences) Multi-proxy reconstructions of Holocene environmental change and catchment biogeochemistry using algal pigments and stable isotopes preserved in lake sediment from Baffin Island and Iceland Thesis directed by Professors Gifford H. Miller and Áslaug Geirsdóttir Lake sediments provide a continuous record of environmental change, integrating information about multiple biogeochemical processes occurring within the lake and catchment. Much of this is recorded by the chemical characteristics of sedimentary organic matter, which can be used as a proxy for past conditions. This dissertation examines Holocene lake sediment records from Baffin Island and Iceland, which, as a result of Arctic amplification feedbacks, are particularly sensitive to changes in climate. We integrated sedimentary algal pigments with more commonly used proxies such as stable isotopes, C:N ratio, and biogenic silica in order to derive a more complete understanding of local climate history and catchment biogeochemistry. Contrasting modern climate conditions between the Eastern Canadian Arctic and Iceland allows us to examine proxy response across different environments. The climate records developed in this study broadly agree with other regional records, with coherent shifts in biogeochemical proxies occurring in response to Holocene climate evolution. The nature, magnitude, and timing of proxy response vary between locations, underscoring the need to account for the distinct environmental factors of each lake system when reconstructing climate history. This study is the first to develop Holocene records of sedimentary algal pigments in each study area which distinctly characterize changes in lacustrine algal group assemblage through time. In Baffin Island, green algae and higher plants are most abundant iii during the early Holocene, with increased diatom relative abundance during the late Holocene and Little Ice Age. This is followed by a return to increased green algae and higher plants during recent times. This pattern is not replicated in Icelandic lakes, where cyanobacteria show the strongest temperature response and are more abundant during warm times. More complete progression of seasonal algal group succession during longer ice-free seasons is the proposed mechanism controlling algal group relative abundance. Recent trends in Icelandic lakes from this study do not show as strong of a response to Anthropogenic warming as on Baffin Island, where many proxies abruptly return to a Holocene Thermal Maximum-like state. The results of this dissertation characterize the biogeochemical regimes which occur during climatic extremes of the Holocene, and can be used to predict future conditions influencing water quality and the carbon cycle in a warming Arctic. iv ACKNOWLEDGMENTS I wish to thank my advisors Giff Miller and Áslaug Geirsdóttir for their guidance, teaching, expertise, and having allowed me the freedom to pursue analytical methods new to our research group; my committee members Julio Sepúlveda, Tom Marchitto, Jim White, and Diane McKnight for their thought provoking questions, comments and advice given during committee meetings and the comprehensive exam; Billy D’Andrea and Jostein Bakke for serving as opponents during the University of Iceland defense; Marilyn Fogel for allowing me to spend months running samples in her lab and teaching me about isotope biogeochemistry; Zoe Sigle for analyzing nearly all of the FTIR-BSi samples; Steve DeVogel for keeping the lab running smoothly and teaching me how to use an HPLC; Rolfe Vinebrooke and Mark Graham for assisting me with the development of algal pigment methodologies at INSTAAR; Thorvaldur Thordarson for assistance with tephra identification; Sveinbjörn Steinthórsson and Thorsteinn Jónsson for excellent field work assistance; John Andrews, Anne Jennings, Scott Lehman, Alex Wolfe and Yarrow Axford for scientific discussions; Sarah Spaulding and Mark Edlund for teaching all about diatoms; fellow graduate students Sarah Crump, Sydney Gunnarson, Darren Larsen, Kurt Refsnider, Kate Zalzal, Simon Pendleton, Leif Anderson, Ben Schupack, Celene Blair, and David Harning for discussion, advice, and friendship; and especially Amy Steiker for her support, encouragement, and willingness to edit many documents over the years. Salary was provided by the Doctoral Grant of the University of Iceland and NSF grant ARC-0909347. This research was made possible by NSF grant ARC-0909347, RANNIS grant of Excellence #141573-051 and several grants awarded to Áslaug Geirsdóttir from the University of Iceland Research Fund. v CONTENTS CHAPTER 1: INTRODUCTION 1.1. INTRODUCTION ........................................................................................................1 1.2. STUDY SITES..............................................................................................................3 1.3. QUESTIONS MOTIVATING THIS DISSERTATION ..............................................5 1.4. RESEARCH METHODS AND GOALS .....................................................................5 1.5. DISSERTATION OVERVIEW..................................................................................11 CHAPTER 2: ALGAL PIGMENTS IN ARCTIC LAKE SEDIMENTS RECORD BIOGEOCHEMICAL CHANGES DUE TO HOLOCENE CLIMATE VARIABILITY AND ANTHROPOGENIC GLOBAL CHANGE 2.1. ABSTRACT ................................................................................................................13 2.2. INTRODUCTION ......................................................................................................15 2.2.1. Regional Holocene Climate .........................................................................17 2.2.2. Study Site .....................................................................................................18 2.3. MATERIALS AND METHODS ................................................................................19 2.3.1 Modern Sampling..........................................................................................19 2.3.2 Sediment Cores .............................................................................................21 2.3.3 Sediment Chronology ...................................................................................21 2.3.4. Sediment Geochemistry ...............................................................................24 2.3.5. Algal Pigments .............................................................................................25 2.3.6. Diatom Preparation and Counting ...............................................................25 2.3.7 Data Analysis ................................................................................................27 2.4. RESULTS ...................................................................................................................28 vi 2.4.1. Chronology ..............................................................................................................28 2.4.2 Sediment Geochemistry ............................................................................................28 2.4.3 Algal Pigments ..........................................................................................................31 2.4.4. Diatom Assemblage Change ....................................................................................33 2.5. DISCUSSION .............................................................................................................35 2.5.1. Pigment and Diatom Preservation ...........................................................................35 2.5.2. Early Holocene (10-7 ka) .........................................................................................37 2.5.3 Mid Holocene (7 ka to 2 ka.......................................................................................38 2.5.4. Late Holocene (2 ka BP to ~1900 AD) ....................................................................40 2.5.5. Anthropocene (~1900 AD to present) ......................................................................40 2.5.6. PCA Analysis ...........................................................................................................41 2.5.7. Comparison with Regional Records ............................................................42 2.6. CONCLUSIONS.........................................................................................................45 2.7. ACKNOWLEDGEMENTS ........................................................................................46