PALEOECOLOGICAL STUDY OF COASTAL MARSH IN THE CHENIER PLAIN, LOUISIANA: INVESTIGATING THE DIATOM COMPOSITION OF HURRICANE-DEPOSITED SEDIMENTS AND A DIATOM-BASED QUANTITATIVE RECONSTRUCTION OF SEA-LEVEL CHARACTERISTICS By KATHRYN E.L. SMITH A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2012 1 © 2012 Kathryn E.L. Smith 2 To my son, Leo 3 ACKNOWLEDGMENTS I gratefully acknowledge the logistical support of the U.S. Geological Survey Center for Coastal and Marine Science in St. Petersburg, Florida, and the National Wetlands Research Center in Baton Rouge and Lafayette, Louisiana. In addition, staff from Rockefeller Wildlife Refuge and Louisiana Department of Natural Resources for granting access to the refuge and aid in sampling. In particular, I wish to thank Molly McLaughlin, Meghan Maraia, Tom Harmon, Carl Taylor and Chandra Dreher for assistance in the lab; Marcy Marot for radioisotope analyses; Sarai Piazza and Greg Steyer for answering countless questions on CRMS and sending me the mud; Leigh Ann Sharp, George Melancon, and Mark Mouledous for assistance in the field; Brady Couvillion for providing access to spatial data; Jim Flocks for letting me run with this project; and Jimmy Johnston and Kim Yates who got me started down this path. I wish to thank the members of my committee: Drs. John Jaeger, Melanie Riedinger-Whitmore and William Wise; you are truly the best group of advisors I could have ever hoped for. Not many people can say they came out of their qualifying exams feeling inspired and excited, but I can. Thank you for your enthusiasm and support. I also want to thank Tom Whitmore for sharing his passion and knowledge of diatoms, and asking for nothing in return. I would not have been able to do any of this if it wasn’t for your help. Most importantly, I thank Dr. Clay Montague for accepting me as a student, inspiring me when I was floundering, sticking with me when I faced challenges, helping me see the bigger picture, and providing an example of the exact type of scientist and educator I will strive to be. My heartfelt thanks go to the following: my parents for never letting me doubt my abilities and making me your first and foremost priority; my brothers, who encouraged 4 my imagination and without which I would not be nearly as resilient and resourceful; to some wonderful friends who provided a much needed compassionate ear and backed me up over the years, each in your own way, when I faced parent-work-school-life challenges: Marti McGuire, Theresa Burress, Kelly Shotts, and Kristine Martella. No matter how far apart we are now or in the future, you’ll always be a part of this journey. And to my son, Leo, thank you for being patient and forgiving me for all those times I couldn’t do what you wanted to do because I had to work on my ‘desert-tation’. I know I have some making up to do. You are my heart and my treasure. 5 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 9 LIST OF FIGURES ........................................................................................................ 11 LIST OF ABBREVIATIONS ........................................................................................... 14 ABSTRACT ................................................................................................................... 16 1 INTRODUCTION .................................................................................................... 18 Motivation ............................................................................................................... 18 Background ............................................................................................................. 19 Louisiana Wetland Loss ................................................................................... 19 Paleoecology .................................................................................................... 21 Hurricanes and Sedimentation ......................................................................... 24 Study Area .............................................................................................................. 27 Chenier Plain .................................................................................................... 27 Rockefeller Wildlife Refuge .............................................................................. 28 Outline of Chapters ................................................................................................. 29 2 STRATIGRAPHIC RECORD AND MICROFOSSIL ANALYSIS OF HURRICANE SEDIMENTATION IN SOUTHWEST LOUISIANA .................................................. 33 Background ............................................................................................................. 33 Regional Setting ..................................................................................................... 36 Methods .................................................................................................................. 38 Identification of Episodic Sedimentation ........................................................... 38 Core Collection ................................................................................................. 40 Laboratory Analysis .......................................................................................... 42 Microfossil Analysis .......................................................................................... 44 Statistical Analyses .......................................................................................... 45 Results .................................................................................................................... 46 Sediment Characteristics and X-radiographs ................................................... 46 Microfossils ....................................................................................................... 49 Discussion .............................................................................................................. 52 3 GEOCHRONOLOGY AND SEDIMENTATION IN AN EVENT-DRIVEN COASTAL MARSH OF SOUTHWEST LOUISIANA ............................................... 69 Background ............................................................................................................. 69 Regional Setting ..................................................................................................... 73 Methods .................................................................................................................. 75 6 Coring and Laboratory Procedures .................................................................. 75 Chronostratigraphic Techniques ....................................................................... 76 Results .................................................................................................................... 78 Sedimentary Characteristics and X-radiographs .............................................. 78 Distribution of 210Pb .......................................................................................... 79 Distribution of 137Cs .......................................................................................... 80 Vertical Accretion Rates ................................................................................... 81 Chronology ....................................................................................................... 82 Mass Accumulation Rates ................................................................................ 82 Discussion .............................................................................................................. 83 4 DIATOM ASSEMBLAGES OF THE CHENIER PLAIN, LOUISIANA: DEVELOPING DIATOM-BASED INFERENCES OF ENVIRONMENTAL CHANGE .............................................................................................................. 102 Background ........................................................................................................... 102 Regional Setting ................................................................................................... 106 Methods ................................................................................................................ 107 Diatom Analysis .............................................................................................. 108 Environmental Variables................................................................................. 109 Statistical Analyses ........................................................................................ 111 Results .................................................................................................................. 115 Diatom assemblages ...................................................................................... 115 Statistical Analysis .......................................................................................... 116 Discussion ............................................................................................................ 120 5 DIATOM-INFERRED SALINITY RECONSTRUCTION FOR COASTAL MARSH IN LOUISIANA’S CHENIER PLAIN .....................................................................