University of Vermont ScholarWorks @ UVM Graduate College Dissertations and Theses Dissertations and Theses 2019 Evaluation of Mysis partial diel vertical migration Brian Patrick O'Malley University of Vermont Follow this and additional works at: https://scholarworks.uvm.edu/graddis Part of the Natural Resources Management and Policy Commons Recommended Citation O'Malley, Brian Patrick, "Evaluation of Mysis partial diel vertical migration" (2019). Graduate College Dissertations and Theses. 996. https://scholarworks.uvm.edu/graddis/996 This Dissertation is brought to you for free and open access by the Dissertations and Theses at ScholarWorks @ UVM. It has been accepted for inclusion in Graduate College Dissertations and Theses by an authorized administrator of ScholarWorks @ UVM. For more information, please contact [email protected]. EVALUATION OF MYSIS PARTIAL DIEL VERTICAL MIGRATION A Dissertation Presented by Brian Patrick O’Malley to The Faculty of the Graduate College of The University of Vermont In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Specializing in Natural Resources January, 2019 Defense Date: October 23, 2018 Dissertation Examination Committee: Jason D. Stockwell, Ph.D., Advisor Sara Helms Cahan, Ph.D., Chairperson Sture Hansson, Ph.D. J. Ellen Marsden, Ph.D. Joe Roman, Ph.D. Cynthia J. Forehand, Ph.D., Dean of the Graduate College © Copyright by Brian Patrick O’Malley January 2019 ABSTRACT Mass animal migrations represent large movements of biomass, energy, and nutrients with predictable patterns and important ecosystem-level consequences. Diel vertical migration (DVM) in aquatic systems, the daily movement of organisms from deeper depths during the day to shallower depths in the water column at night, is widespread in freshwater and marine systems. Recent studies, however, suggest partial migration behavior, whereby only some portion of a population migrates, is the rule rather than the exception in a range of migratory fauna, including those that undergo DVM. Hypotheses to explain why partial migrations occur complicate traditional views on DVM and challenge conventional theories. I address intraspecific variation in DVM behavior of an aquatic omnivore, Mysis diluviana, to test several long-standing assumptions about benthic-pelagic DVM in Mysis. I evaluated the extent of partial DVM and several potential drivers within a Lake Champlain Mysis population. I used traditional net-based field observations, a novel deep-water video camera system, and a laboratory experiment, to compare distributions, demographics, abundance estimates, hunger-satiation state, and feeding behavior, of migrant and non-migrant Mysis across multiple seasons, habitats, and different times of the day. Findings from my dissertation suggest Mysis partial DVM is common, and is associated with body size and demographic differences among individuals. Partial DVM behavior, however, did not correspond to strong differences in feeding preference or hunger-satiation state of individuals. My results contribute toward a more comprehensive understanding of migration theory and mysid biology, by including the often overlooked, but important, benthic habitat component of DVM studies, and fills in several ecological knowledge gaps regarding a key omnivore in many deep lake food webs across North America where Mysis serve as both predators and prey to many organisms. CITATIONS Material from this dissertation has been published in the following form: O’Malley, B. P., Hansson, S. and Stockwell, J. D.. (2018). Evidence for a size-structured explanation of partial diel vertical migration in mysids. Journal of Plankton Research 40: 66-76. O’Malley, B. P., Dillon, R. A., Paddock, R. W., Hansson, S. and Stockwell, J. D.. (In Press). An underwater video system to assess abundance and behavior of epibenthic Mysis. Limnology and Oceanography: Methods. DOI: 10.1002/lom3.10289 ii ACKNOWLEDGEMENTS I would like to thank my advisor, Jason Stockwell, for the opportunity to conduct graduate research at the Rubenstein Ecosystem Science Laboratory. I thank you for the motivation, guidance, and writing tips you have instilled upon me, and look forward to future collaborations and beyond. Perhaps the most crucial element to accomplishing my field work has been captain Steve Cluett. Steve’s wisdom, expertise, and enthusiasm, was instrumental for all aspects of my project. Along with Steve, deckhands Krista Hoffsis and Brad Roy were also critical. I’ll treasure our conversations aboard the R/V Melosira while sipping coffee and looking back at Burlington on those long nights of Mysis sampling. I would like to acknowledge several of my past supervisors and colleagues who continue to motivate me throughout my journey to pursue science as a career. Conversations with David Bunnell formed the impetus for my interest in Mysis. Mentors from my Lake Ontario stint (Lars Rudstam, Jim Watkins, and Brian Weidel), were influential in shaping my career path. Great after-work discussions with friends Bryan Maitland and Elliot Jackson, while fishing or talking zooplankton, were pivotal in my motivation to pursue graduate studies. Additionally, I thank members of my committee (Sure Hansson, Sara Helms Cahan, Ellen Marsden, and Joe Roman) for their help in shaping my project. I’ve learned so much from collaborating with all of you, and I will continue to benefit from all these past experiences. I thank the support of my parents Mark and Ewa O’Malley as they opened the initial door to research by supporting me as I pursued my undergraduate degree. That iii initial launch into undergraduate research and study was how I discovered a career in aquatic research, and ultimately found my niche in large lake research. None of that would have been possible without their support. I thank Rebecca Dillon for her efforts to get the Mysis video camera system up and running, which helped pave the way for a concept to become a reality. Additionally, several undergraduates: Pascal Wilkins, Kevin Melman, Hannah Lister, Grace Scorpio, Jeni Knight, and Jessica Griffin; provided substantial help and provided me with opportunities to learn about myself and hone my skills as a mentor. I hope the research experiences were equally rewarding for you as they were for me. Funding was provided by the Great Lakes Fishery Commission with the assistance of Senator Patrick Leahy. Additional funding was provided by a University of Vermont Chrysalis Award, and a scholarship from the International Association for Great Lakes Research. Lastly, and most importantly, I would like to thank my girlfriend Nikki Saavedra for her love and support during our long-distance lifestyle these past several years while we worked on our degrees. Your support, patience, and laughter throughout this process has been amazing. I look forward to starting our next chapter in life together. iv TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ............................................................................................... iii LIST OF TABLES ........................................................................................................... viii LIST OF FIGURES ............................................................................................................ x CHAPTER 1: DIEL VERTICAL MIGRATION AND MYSID ECOLOGY FROM A PARTIAL MIGRATION PERSPECTIVE ......................................................................... 1 Diel vertical migration: examples, hypotheses, and conceptual framework .................. 3 Mysis ecology: distribution and vertical migration behavior .......................................... 6 Trophic role of Mysis in food webs .............................................................................. 12 The need for a partial DVM approach to mysid ecology .............................................. 15 Lake Champlain as a study system ............................................................................... 17 Dissertation outline ....................................................................................................... 19 References ..................................................................................................................... 22 CHAPTER 2: EVIDENCE FOR A SIZE-STRUCTURED EXPLANATION OF PARTIAL DIEL VERTICAL MIGRATION IN MYSIDS.............................................. 34 Abstract ......................................................................................................................... 35 Introduction ................................................................................................................... 36 Methods......................................................................................................................... 39 Results ........................................................................................................................... 43 Discussion ..................................................................................................................... 49 Conclusions ................................................................................................................... 55 Acknowledgements ....................................................................................................... 55 References ..................................................................................................................... 57 v CHAPTER 3: AN UNDERWATER VIDEO SYSTEM TO ASSESS ABUNDANCE AND BEHAVIOR OF EPIBENTHIC MYSIS .................................................................