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Biogeochemistry of a Saline, Alkaline, Terminal Lake Ecosystem In UNLV Theses, Dissertations, Professional Papers, and Capstones 8-1-2016 Biogeochemistry of a Saline, Alkaline, Terminal Lake Ecosystem in Transition; Walker Lake, Nevada Katherine Lynn Willever University of Nevada, Las Vegas, [email protected] Follow this and additional works at: https://digitalscholarship.unlv.edu/thesesdissertations Part of the Fresh Water Studies Commons, and the Microbiology Commons Repository Citation Willever, Katherine Lynn, "Biogeochemistry of a Saline, Alkaline, Terminal Lake Ecosystem in Transition; Walker Lake, Nevada" (2016). UNLV Theses, Dissertations, Professional Papers, and Capstones. 2817. https://digitalscholarship.unlv.edu/thesesdissertations/2817 This Thesis is brought to you for free and open access by Digital Scholarship@UNLV. It has been accepted for inclusion in UNLV Theses, Dissertations, Professional Papers, and Capstones by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. BIOGEOCHEMISTRY OF A SALINE, ALKALINE, TERMINAL LAKE ECOSYSTEM IN TRANSITION; WALKER LAKE, NEVADA, USA By Katherine Lynn Willever Bachelor of Science — Biological Sciences York College of Pennsylvania 2012 A thesis submitted in partial fulfillment of the requirements for the Master of Science — Biological Sciences School of Life Sciences College of Sciences The Graduate College University of Nevada, Las Vegas August 2016 Copyright 2016 by Katherine L. Willever All Rights Reserved Thesis Approval The Graduate College The University of Nevada, Las Vegas July 14, 2016 This thesis prepared by Katherine Lynn Willever entitled Biogeochemistry of a Saline, Alkaline, Terminal Lake Ecosystem in Transition; Walker Lake, Nevada, USA is approved in partial fulfillment of the requirements for the degree of Master of Science – Biological Sciences School of Life Sciences Brian P. Hedlund, Ph.D. Kathryn Hausbeck Korgan, Ph.D. Examination Committee Chair Graduate College Interim Dean Dennis A. Bazylinski, Ph.D. Examination Committee Member Duane Moser, Ph.D. Examination Committee Member Elisabeth Hausrath, Ph.D. Graduate College Faculty Representative ii ABSTRACT BIOGEOCHEMISTRY OF A SALINE, ALKALINE, TERMINAL LAKE ECOSYSTEM IN TRANSITION; WALKER LAKE, NEVADA, USA By Katherine L. Willever Dr. Brian P. Hedlund Dr. Duane P. Moser Graduate Advisory Committee Chair Principal Investigator Professor of Biology Associate Research Professor University of Nevada, Las Vegas Desert Research Institute Walker Lake is a saline, alkaline, terminal lake ecosystem located in west-central Nevada. For over one hundred years, anthropogenic streamflow diversions within the Walker River Basin have ultimately led to little or no water reaching Walker Lake, the basin’s terminus for water flow. These diversions have resulted in a >46 meter decrease in the lake surface altitude and increases in salinity and dissolved salt constituents that have caused the elimination of native fish species. This study examines how the lack of freshwater inflow has altered the physical, chemical, and microbiological structure of Walker Lake during the lake’s ongoing desiccation. Between 2007 and 2015, water and sediment samples were collected from a central lake location of Walker Lake, coinciding with the historical timing of late summer thermal stratification. Physical parameters and chemical constituent measurements show Walker Lake to have shifted from a monomictic to a polymictic system sometime after 2008, with salinity increasing conservatively to values over 21 g L-1 in 2015. Illumina sequencing of the V4 region of the 16S rRNA gene was completed on all environmental filter and sediment samples to iii observe trends and changes in the microbial populations of the water column and sediment as a result of the changing lake dynamics. Over time, distinct differences in overall community composition and diversity were observed between sampling dates. The sediment communities were found to be highly dissimilar from the overlying pelagic microbial communities and showed more similarity to microbial communities from anoxic hypolimnion water samples from the 2008 sampling event when lake stratification was observed. The anthropogenic and climatic factors that Walker Lake has faced over the past century have dramatically altered the ecosystem. This study aims to contribute to the overall understanding of the Walker River Basin and to other terminal lake basins throughout the world. By examining the microbial communities of Walker Lake and documenting the limnological shift of this transitioning ecosystem, we gain insights into the physiological aspects of Walker Lake and possible ways to manage and restore this unique environment to the thriving ecosystem it once was. iv ACKNOWLEDGEMENTS Many people have helped make this document possible. My mentor on this project, Dr. Duane Moser, has been the cornerstone of my graduate success and I am grateful for his guidance through this interesting project and for introducing me to the amazing fields of limnology and environmental microbiology. The members of my graduate committee, Drs. Brian Hedlund, Dennis Bazylinski, and Elisabeth Hausrath, have given me incredible feedback and advice and were always willing to sit down and discuss the development and progress of my research. Current and previous lab members at DRI have been extremely helpful, especially past lab post-doctoral members Dr. Jen Fisher, who dedicated a lot of her time collecting and analyzing much of the Walker Lake data from 2007 and 2008, and Dr. Scott Hamilton-Brehm, who helped me learn numerous valuable laboratory techniques. Joshua Sackett, a current DRI lab member and Ph.D. student, has provided immense bioinformatic support for this research and has been a great friend throughout this process. This research has been primarily funded by the U.S. Fish and Wildlife Service (USFWS) and I am very grateful for their support and continued interest in the Walker River Basin system. USFWS members Lisa Heki and Derek Bloomquist have been particularly instrumental in securing funds and helping with sampling efforts. I would also like to thank my family, friends, and Kyle for their continuous encouragement, love, and support. There are many other wonderful people who have helped me throughout this project in numerous other ways. Thank you everyone, for everything! v TABLE OF CONTENTS ABSTRACT ................................................................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................................ v LIST OF TABLES ....................................................................................................................... viii LIST OF FIGURES ........................................................................................................................ x CHAPTER ONE ............................................................................................................................. 1 Salinity and Alkalinity in Aqueous Environments ...................................................................... 1 Biological Diversity in Aquatic Ecosystems and Response to Environmental Fluctuations ...... 3 Hydrogeology of the Great Basin and Walker River Basin ........................................................ 5 Climate of the Walker River Basin ............................................................................................. 7 Paleohydrology............................................................................................................................ 8 Recent Lake-Level Fluctuations and Impacts ........................................................................... 11 Comparison of Walker Lake to Other Saline Lakes ................................................................. 14 Methods Used to Address Microbial Diversity ......................................................................... 17 CHAPTER TWO .......................................................................................................................... 20 Graduate Student’s Involvement and General Background ...................................................... 21 Abstract ..................................................................................................................................... 23 Introduction ............................................................................................................................... 24 Materials and Methods .............................................................................................................. 26 Results ....................................................................................................................................... 35 Discussion ................................................................................................................................. 57 Conclusions ............................................................................................................................... 66 Acknowledgements ................................................................................................................... 67 CHAPTER THREE ...................................................................................................................... 68 Graduate Student’s Involvement and General Background ...................................................... 69 vi Abstract ....................................................................................................................................
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