SALT MARSH DIEBACK: THE RESPONSE OF SPARTINA ALTERNIFLORA TO DISTURBANCES AND THE CONSEQUENCES FOR MARSH INVERTEBRATES by CAROLINE ROCHESTER MCFARLIN (Under the Direction of Merryl Alber) ABSTRACT Spartina alterniflora is a foundation species that plays a disproportionately critical role in salt marshes, as it ameliorates chemical and physical stress to other plants and animals, provides essential habitat, protection from predators, and a source of organic matter to associated fauna. Disturbances including sudden dieback, herbivore overgrazing, and wrack deposition can lead to a loss of Spartina and thus, indirectly affect the invertebrate community. My goals were 1) to examine the effects on the invertebrate communities in 2 different geographical regions (GA, LA) and among 4 different disturbances within a region (GA), 2) to determine whether various disturbances would elicit a similar and predictable physiological response (the DMSO:DMSP ratio, and metal load) in Spartina that could be used as a sensitive and predictable indicator of stress among various disturbance types, and 3) to document the never before described long-term trajectory and patterns of recovery from sudden dieback in a Spartina and Juncus roemerianus marsh. Spartina loss in GA and LA led to similar decreases in Littoraria irrorata (periwinkle snails), but there were strong differences in the responses of infauna between the states and among years. These results suggested context-dependency in both the effect of foundation species within a geographical region and in the evaluation of the ecosystem service provided at the time of sampling. Overall and despite differing results, it was found that Spartina was ultimately was important in maintaining the invertebrate communities in both states. However, within a geographical region, both the physiological response of Spartina and the indirect response of the invertebrates to Spartina loss were similar and predictable among four different disturbances. The DMSO:DMSP ratio and metal loads were increased in affected Spartina plants often responsive in otherwise green leaves) and periwinkle snails and benthic macroinfauna (density, taxon richness, and diversity) were significantly decreased in affected areas, regardless of disturbance type. Vegetation recovery at sudden dieback is occurring slowly (on the order of a decade) via rhizomes extension from healthy areas, and thus understanding the effects to invertebrates is important, as disturbances such as these are expected to increase with climate change and anthropogenic effects. INDEX WORDS: foundation species, salt marsh dieback, Spartina alterniflora , Juncus roemerianus , benthic macroinfauna, Littoraria irrorata , DMSP, DMSO, metals, chlorophyll a SALT MARSH DIEBACK: THE RESPONSE OF SPARTINA ALTERNIFLORA TO DISTURBANCES AND THE CONSEQUENCES FOR MARSH INVERTEBRATES by CAROLINE ROCHESTER MCFARLIN B.S.A., The University of Georgia, 2000 M.S., The University of Georgia, 2004 A Dissertation Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY ATHENS, GEORGIA 2012 © 2012 Caroline Rochester McFarlin All Rights Reserved SALT MARSH DIEBACK: THE RESPONSE OF SPARTINA ALTERNIFLORA TO DISTURBANCES AND THE CONSEQUENCES FOR MARSH INVERTEBRATES by CAROLINE ROCHESTER MCFARLIN Major Professor: Merryl Alber Committee: T. Dale Bishop Jeb Byers William Fitt Steven C. Pennings Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia May 2012 DEDICATION To the loves of my life ~ Brady and Chip. iv ACKNOWLEDGEMENTS First, I would like to my family for their love and support – without them, this dissertation would not have been possible. I would also like to sincerely thank my advisor Merryl Alber who has been a great friend and mentor over the years. She is also an excellent editor, and although I didn’t always look forward to writing yet another draft, she greatly improved this dissertation. I owe her a new pack of pencils! I thank my Alber Lab office mates past and present – Christine, Sylvia, Justine, and Natalie – for all of their encouragement and support over the years – they are the BEST and always keep me laughing! I thank Dale Bishop for patiently teaching me the infaunal invertebrate taxonomy and for good conversation, but mostly for the wonderful, gourmet meals that he shared with me while on Sapelo Island (especially after a long day of work in the marsh). I thank Joan Sheldon, Steve Pennings, and Susan Alber for statistical advice. I thank my Ph.D. committee for volunteering their time and for providing useful suggestions. I also thank all of those who have helped me with lab and field work along the way, especially Zane Cress, Ashley Rich-Robertson, Caitlin Yeager, Sylvia Schaefer, Christine Hladik, Galen Kaufman, Kristen Anstead, Jacob Shalack, Jenny Fenton, Galen Kaufman, and Trey Kenemer. I thank both the Moran and Whitman labs (and especially Leong-Keat Chan and Chris Reisch) for providing access to lab equipment and for helping me with methodology for Spartina DMSP analysis. I thank both John Fry and Doug Hoffman of Cumberland Island NPS for providing me with access to field sites. I v thank the Georgia Coastal Ecosystems (GCE) – LTER for funding my dissertation work. Last of all, I am thankful for Red Bull, Monster Energy, and Starbucks for providing me with the final push to the finish! vi . Oh, what is abroad in the marsh and the terminal sea? Somehow my soul seems suddenly free . An excerpt from “The Marshes of Glynn” Sydney Lanier, 1878 vii TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ................................................................................................ v CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW ............................... 1 1.1. Background............................................................................................ 1 1.2. Marsh Disturbances ............................................................................... 2 1.3. Plant Stressors in Salt Marshes.............................................................. 5 1.4. Overview of Dissertation....................................................................... 7 References..................................................................................................... 8 2 THE EFFECT OF SUDDEN MARSH DIEBACK ON THE BENTHIC INVERTEBRATE COMMUNITIES OF SPARTINA ALTERNIFLORA SALT MARSHES ..................................................... 13 Abstract....................................................................................................... 14 2.1. Introduction.......................................................................................... 16 2.2. Methods ............................................................................................... 19 2.3. Results.................................................................................................. 24 2.4. Discussion............................................................................................ 32 2.5. Conclusions.......................................................................................... 41 2.6. Acknowledgments ............................................................................... 43 viii References................................................................................................... 44 3 DMSO:DMSP RATIOS AND METAL CONTENT AS POTENTIAL INDICATORS OF STRESS IN SPARTINA ALTERNIFLORA........... 60 Abstract....................................................................................................... 61 3.1. Introduction.......................................................................................... 63 3.2. Methods ............................................................................................... 67 3.3. Results.................................................................................................. 73 3.4. Discussion............................................................................................ 79 3.5. Conclusions.......................................................................................... 87 References................................................................................................... 88 4 THE EFFECT OF DISTURBANCE ON INVERTEBRATE ASSEMBLAGES IN GEORGIA SALT MARSHES .......................... 108 Abstract..................................................................................................... 109 4.1. Introduction........................................................................................ 111 4.2. Methods ............................................................................................. 114 4.3. Results................................................................................................ 119 4.4. Discussion.......................................................................................... 126 4.5. Conclusions........................................................................................ 134 References................................................................................................. 136 5 SALT MARSH DIEBACK IN GA: SEVEN YEARS OF OBSERVATIONS................................................................................... 155 Abstract..................................................................................................... 156 5.1. Introduction.......................................................................................