The effects of the non-native invertebrate predator Bythotrephes longimanus and declining aqueous calcium on crustacean zooplankton communities in Canadian Shield lakes By Shakira Stephanie Elaine Azan A thesis submitted to the Graduate Program in Biology in conformity with the requirements for the Degree of Doctor of Philosophy Queen’s University Kingston, Ontario, Canada October 2016 ©Shakira Stephanie Elaine Azan, 2016 Abstract Over the last several decades, human activities have resulted in environmental changes that have increased the number of stressors that can act on a single environment. In Canadian Shield lakes, two recent stressors, the invasion of Bythotrephes longimanus and calcium decline, have been documented. Widespread acidification of hundreds of North American lakes has resulted in the precipitous decline of lake water calcium concentration. Crustacean zooplankton with high calcium demands are likely to be vulnerable to calcium decline, especially <1.5 mg Ca/L, where survival and reproduction rates are reduced. These taxa are also vulnerable to predation by Bythotrephes that has been implicated in the loss of pelagic biodiversity in soft water lakes. Despite laboratory and field studies aimed at understanding the independent impact of these stressors, it is unclear how their co-occurrence will influence community response. Using a combination of data from a large regional lake survey and field experiments, I examined the individual and joint effects of Bythotrephes and calcium decline on native zooplankton community structure. Results demonstrated that much is known about Bythotrephes and our findings of reduced total zooplankton and species richness, due to the loss of Cladocera, are consistent with field surveys and other experimental studies. While we did not detect strong evidence for an effect of calcium on zooplankton using the lowest calcium concentration among invaded lakes (1.2 mg Ca/L), there is evidence that, as lake water calcium concentrations fall <1 mg Ca/L, per capita growth rates of a broad variety of taxa are expected to decline. At the regional scale, negative effects of Bythotrephes and calcium on abundances of small cladocerans and Daphnia pulicaria, respectively, were in agreement with my experimental observations. We also observed significant interactions between Bythotrephes and calcium for a broad variety of taxa. As Bythotrephes continues to spread and invade lakes that are also declining in aqueous calcium, both stressors are i likely to amplify negative effects on Cladocera that appear the most vulnerable. Loss of these important zooplankton in response to both Bythotrephes and calcium decline, is likely to lower zooplankton productivity, with potential effects on phytoplankton and higher trophic levels. ii Co-Authorship This thesis conforms to the Manuscript format as outlined by the School of Graduate Studies and Research, with a single Acknowledgement and Reference sections. Manuscripts and their co- authors that are a result of this thesis are listed below. Chapter 2: Drs. Shelley Arnott and Norman Yan provided guidance on data presentation and editorial advice. Chapters 3, 4, and 5: Dr. Shelley Arnott assisted in the conception and design of the field experiments, and provided advice on data analyses, interpretation of results, and revisions to manuscripts. Chapter 5: Drs. Shelley Arnott and Norman Yan provided water chemistry and crustacean zooplankton data from the large regional lake survey conducted by the Canadian Aquatic Invasive Species Network in the Muskoka River Watershed. Manuscripts directly from this thesis: Azan SSE, SE Arnott, and ND Yan. (2015). A review of the effects of Bythotrephes longimanus and calcium decline on zooplankton communities – can interactive effects be predicted? Environmental Reviews 23: 395-413. Azan SSE and SE Arnott. (2016). The effects of Bythotrephes longimanus and calcium decline on crustacean zooplankton communities in Canadian Shield lakes. Hydrobiologia, DOI: 10.1007/s10750-016-2934-0. Azan SSE and SE Arnott. The impact of declining aqueous calcium on population growth rates of crustacean zooplankton using experimental mesocosms. Limnology and Oceanography. In review. iii Azan SSE, SE Arnott, and ND Yan. Effects of the invasive zooplanktivore Bythotrephes longimanus and lake calcium gradients on crustacean zooplankton across southern Ontario regional landscape. In preparation for Freshwater Biology. Manuscripts indirectly from this thesis: Arnott SE, SSE Azan, and A Ross. Regional calcium decline reduces population growth rates of zooplankton. Canadian Journal of Zoology. In review. iv Acknowledgements To my supervisors, Drs. Shelley Arnott and Norman Yan, I extend my gratitude for your continuous support, guidance and encouragement over the past four years. This journey would not have been the same without both of you. As mentors and friends, you were there through difficult field seasons, data analyses, countless emails, providing constructive critiques on my manuscripts, and above all, I have gained, “by standing on the shoulders of giants”. I also wish to thank my committee members, Drs. John Smol and Paul Grogan, for their feedback and advice over the past four years. My field seasons would not have been successful without the contributions of past and present staff members of the Ministry of the Environment and Climate Change, Dorset Environmental Science Centre, Dorset, Ontario. I extend my gratitude to Keith Somers, Jim Rusak, Ron Ingram, Marilyn Velenosi, Don Evans, Cathy Thompson, Ron Xu, Peter Sutey, Andrew Paterson, Chris Jones, Tim Field, Chris McConnell, Huaxia Yao, Carmen Pereira, and Rick Mercks who provided logistical support, assistance and advice during my field seasons. I also wish to thank the interns in the Chemistry lab at Dorset – Katie Paroschy and Madison Bell for providing me with numerous water chemistry results during my second field season. To my field assistants, Philip Anderson, Matthew Laird and for a short while, Adam Sprott, Miranda Chen, and Thomas Van Zuiden, I could not have survived my field seasons without your assistance, strengths, and most of all, your friendship. I also thank Martha Celis for her guidance in keeping my Daphnia alive during my second field season. Through your guidance and support, my experiment was saved before it began and for this, I am indebted to you. v Many thanks to all past and present graduate students of the Arnott Lab for their support, feedback, and friendship over the years, Anneli Jokela, Brian Kielstra, Kimberly Lemmen, Sarah Hasnain, Alex Ross, Michele Nicholson, Mike Lavender, Melanie Overhill, and Erin Suenaga. I wish to say a special thank you to James Sinclair, for your friendship inside and outside of the lab, for answering countless R questions and taking the time to explain and solve the simplest of problems. In addition, thanks to Moumita Karmakar and Branaavan Sivarajah from the PEARL Lab that made some of my crazy days so much better. To my family and friends for their overwhelming support and guidance, but even more so, for being an integral part of my life. Thank you for countless prayers, motivational videos, text messages, and phone and skype calls of encouragement and for reminding me that “a gem cannot be polished without friction, nor a man perfected without trials”. Last, and by no means least, I thank my heavenly Father for, his unceasing support, setting me on this journey, and allowing me to fulfil the requirements of this PhD programme – thank you! vi Table of Contents Abstract ............................................................................................................................................ i Co-Authorship................................................................................................................................ iii Acknowledgements ......................................................................................................................... v Table of Contents .......................................................................................................................... vii List of Tables ................................................................................................................................. xi List of Figures .............................................................................................................................. xiii List of Abbreviations ................................................................................................................... xvi Chapter 1 General Introduction .................................................................................................. 1 MULTIPLE STRESSORS .......................................................................................................... 2 STRESSORS ON THE CANADIAN SHIELD .......................................................................... 3 Invasion history and biology of Bythotrephes ......................................................................... 6 Calcium decline ..................................................................................................................... 10 Interaction between Bythotrephes and calcium decline? ....................................................... 12 CRUSTACEAN ZOOPLANKTON ......................................................................................... 14 THESIS OBJECTIVES ............................................................................................................