University of Mississippi eGrove Electronic Theses and Dissertations Graduate School 1-1-2018 Effects of Hydrological Connectivity on the Benthos of a Large River (Lower Mississippi River, USA) Audrey B. Harrison University of Mississippi Follow this and additional works at: https://egrove.olemiss.edu/etd Part of the Biology Commons Recommended Citation Harrison, Audrey B., "Effects of Hydrological Connectivity on the Benthos of a Large River (Lower Mississippi River, USA)" (2018). Electronic Theses and Dissertations. 1352. https://egrove.olemiss.edu/etd/1352 This Dissertation is brought to you for free and open access by the Graduate School at eGrove. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of eGrove. For more information, please contact [email protected]. EFFECTS OF HYDROLOGICAL CONNECTIVITY ON THE BENTHOS OF A LARGE RIVER (LOWER MISSISSIPPI RIVER, USA) A Dissertation presented in partial fulfillment of requirements for the degree of Doctor of Philosophy in the Department of Biological Sciences The University of Mississippi by AUDREY B. HARRISON May 2018 Copyright © 2018 by Audrey B. Harrison All rights reserved. ABSTRACT The effects of hydrological connectivity between the Mississippi River main channel and adjacent secondary channel and floodplain habitats on macroinvertebrate community structure, water chemistry, and sediment makeup and chemistry are analyzed. In river-floodplain systems, connectivity between the main channel and the surrounding floodplain is critical in maintaining ecosystem processes. Floodplains comprise a variety of aquatic habitat types, including frequently connected secondary channels and oxbows, as well as rarely connected backwater lakes and pools. Herein, the effects of connectivity on riverine and floodplain biota, as well as the impacts of connectivity on the physiochemical makeup of both the water and sediments in secondary channels are examined. Between June 2014 and August 2016, twenty-six sites spanning a gradient of hydrological connectivity to the main channel of the Mississippi River were sampled. First, macroinvertebrate community structure across the floodplain was analyzed, and a strong association between community types present and frequency of connection was found. Next, the effects of hydrologic connectivity on macroinvertebrate communities in secondary channels was investigated. These results indicate the loss of connectivity through seasonal disconnection of secondary channels from the main channel causes a shift from a lotic to lentic environment, and then a legacy effect, a macroinvertebrate ii void, when connectivity is restored. Finally, connectivity also affects the physiochemical dynamics of water and sediments within secondary channels, transforming disconnected channels into backwater habitats, characterized by warmer temperatures, lower dissolved oxygen concentrations, and sediments rich in organic matter. Colonization of these new pools and slackwater habitats by lentic macroinvertebrate communities occurs, but both the community changes and changes in the nutrient load and sediment makeup are temporary, only persisting until reconnection to the river channel occurs. iii DEDICATION This work is dedicated to my family. Without your continued support, this project would not have been possible. I express my deepest gratitude for sharing in my burdens and successes, for reducing my workload whenever possible, and for making yourselves available when needed or asked. Through me, may my dearest Eleanor see that she can accomplish what she works hard for, and through you, may she see that such achievements are rarely, if ever, done by oneself. iv LIST OF ABBREVIATIONS AND SYMBOLS ANOVA – Analysis of Variance AWI – America’s Watershed Initiative; A multi-agency working group focused on determining, monitoring, and improving the health of the Mississippi River Watershed. CPUE – Catch Per Unit Effort: An indirect comparison of sample abundance in a single effort between different gear types. ERDC – US Army Engineer Research and Development Center, Vicksburg, MS GIS – Geographic Information System Km – Kilometer LiDAR – Light Detection and Ranging LMR – Lower Mississippi River: The free-flowing Mississippi River from its confluence with the Ohio River at Cairo, IL, to its mouth at the Gulf of Mexico. LMRCC – Lower Mississippi River Conservation Committee nMDS – Non-metric Multidimensional Scaling mMDS – Metric Multidimensional Scaling PCA – Principle Components Analysis PERMANOVA – Permutational Multivariate Analysis of Variance v Rkm – River kilometer RM – River Mile: Unit of measurement used in USACE Navigation Charts, beginning at RM 0 at the Head of Passes near Venice, LA, to RM 953.5 at the confluence with the Ohio River at Cairo, IL. SIMPER – Similarity Percentages Procedure USACE – United States Army Corps of Engineers USFWS – United States Fish and Wildlife Service WSE – Water Surface Elevation (ft) vi ACKNOWLEDGEMENTS I would first like to thank my advisor, Dr. Cliff Ochs, for his guidance throughout the last five years. I could not have hand-picked a more perfect fit for this position. Dr. Ochs has allowed me the space I need to think, provided me the resources I needed to work and travel, labored with me in the field and laboratory, and offered me the advice and support I needed to stay productive, all while treating me with the respect of a colleague. I look forward to many more years of collaboration and friendship, though hopefully no more middle of the night water filtration. I am also very grateful for the feedback and support of my committee members in the Department of Biology – Dr. Paul Lago and Dr. Marjorie Holland. Dr. Lago graciously allowed me space in his lab and gave me invaluable teaching experience. I also thank my committee member Dr. Gregg Davidson of the Department of Geology. My project would not have been feasible without the support of my colleagues at the Fish Ecology Team at the US Army Engineer Research and Development Center in Vicksburg, MS. Dr. Todd Slack has been one of my biggest advocates since I began my scientific career. Not only has he served as a reliable committee member throughout my graduate studies, he has also been an insightful mentor and friend. Perhaps most importantly, however, he introduced me to pivot tables and Access, neither of which I vii could do without. Our team is led by Dr. Jack Killgore, whom I would like to thank for allowing me the freedom to expand the work of our group to include my research interests. I thank Bradley Lewis and Jay Collins for their tireless work in both the logistical and physical field sampling efforts. I also thank Dr. Catherine Murphy for helping with the statistical analyses included in my study. Amanda Oliver graciously extended her GIS wisdom to me and calculated my post hoc connectivity metrics. This project was primarily funded through the Mississippi River Geomorphology and Potamology Program of the US Army Corps of Engineers Mississippi Valley Division directed by Dr. Barb Kleiss (Retired) and Dr. Ty Wamsley. Other sources of funding include a research internship with the National Great Rivers Research and Education Center in Alton, IL, and a writing fellowship awarded by the University of Mississippi Graduate School. I owe my career, my affection for aquatic insects, and my love for exploring rivers and streams to my longtime mentor, Dr. Bill Stark of Mississippi College in Clinton, MS. I cannot say enough about the impression Dr. Stark has had on me – on both my profession and as a person. Dr. Stark is an exemplary human being in all regards, and is the most productive scientist I know. It has been my great honor to work with him, travel the country with him, and especially to learn from him. I will continue to strive to mirror his ethic, patience, temperament, and efficiency. My special thanks and appreciation go to my sister, Lauren Leonard. I always dreamed of having her be my personal assistant, and many times over the last five years, she has gone above and beyond that role. Lauren has been a steadfast, capable helper to me throughout my project. She helped me work more efficiently and I am indebted to viii her. My friend, Dr. Reese Worthington shared his office space and a listening ear, allowed me to bounce off ideas for research, and to vent about anything and everything. I look forward to entomological collaborations for years to come. Finally, Sam Testa at the USDA Sedimentation Laboratory in Oxford, MS, kindly allowed me use of their facility and processed sediment samples for me. ix TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii DEDICATION ................................................................................................................... iv LIST OF ABBREVIATIONS AND SYMBOLS ............................................................... v ACKNOWLEDGEMENTS .............................................................................................. vii LIST OF TABLES ............................................................................................................ xii LIST OF FIGURES ......................................................................................................... xiv CHAPTER I: INTRODUCTION ........................................................................................ 1 CHAPTER II: RELIABLE AND EFFECTIVE SAMPLING GEAR TYPE FOR LARGE