THE ECOLOGICAL FUNCTIONING OF SOUTHERN OCEAN PTEROPODS AND THE USE OF NOVEL FIELD- AND LABORATORY-BASED APPROACHES By Christine Kim Weldrick, BSc (UBC), MSc (UVic) Submitted in fulfilment of the requirements for the Degree of Doctor of Philosophy University of Tasmania Date 16 October 2019 i “And what’s more, they are all still smiling despite the long hours, roasting air temperatures, questionable coffee dispensed by the machine in the corridor and, for many of them, the repetitive, mind-numbing tasks—like counting sea butterflies.” Helen Scales Spirals in Time: The Secret Life and Curious Afterlife of Seashells ii Statements and Declarations Declaration of Originality This thesis contains no material which has been accepted for a degree or diploma by the University or any other institution, except by way of background information and duly acknowledged in the thesis, and to the best of my knowledge and belief, no material previously published or written by another person where due acknowledgement is made in the text of the thesis, nor does the thesis contain any material that infringes copyright. Statement of Authority of Access The publishers of the papers comprising Chapters 2 and 3 hold the copyright for that content. Access to the material should be sought from the respective journals. The remaining non- published content of the thesis may be made available for loan and limited copying in accordance with the Copyright Act 1968. Statement regarding published work contained in thesis The publishers of the papers comprising Chapters 2 and 3 hold the copyright for that content, and access to the material should be sought from the journal. The remaining non published content of the thesis may be made available for loan and limited copying and communication in accordance with the Copyright Act 1968. Statement of Ethical Conduct The research associated with this thesis abides by the international and Australian codes on human and animal experimentation, the guidelines by the Australian Government's Office of the Gene Technology Regulator and the rulings of the Safety, Ethics and Institutional Biosafety Committees of the University. All research conducted for this thesis was approved by the University of Tasmania Animal Ethics Committee (Permit No. A0010843). Signed: Christine K. Weldrick Date: 16 October 19 iii Statement of co-author contributions The following people and institutions contributed to the publication of work undertaken as part of this thesis: Christine K. Weldrick, Institute for Marine & Antarctic Studies, UTas Dr. Kerrie M. Swadling, Institute for Marine & Antarctic Studies, UTas Dr. Rowan Trebilco, Institute for Marine & Antarctic Studies, UTas Dr. Diana M. Davies, CSIRO Oceans and Atmosphere, Hobart, TAS Publications result from research, author details and their roles: Paper 1, Can lipid removal affect interpretation of resource partitioning from stable isotopes in Southern Ocean pteropods? Reproduced in Chapter 2; published in Rapid Communications in Mass Spectrometry – Wiley Publishing: Weldrick, C.K., Trebilco, R., Swadling, K.M., 2019. Can lipid removal affect interpretation of resource partitioning from stable isotopes in Southern Ocean pteropods? Rapid Communications in Mass Spectrometry. doi: 10.1002/rcm.8384 Christine K. Weldrick (70%) Dr. Kerrie M. Swadling (15%) Dr. Rowan Trebilco (15%) Paper 2, Trophodynamics of Southern Ocean pteropods on the southern Kerguelen Plateau Reproduced in Chapter 3; published in Ecology & Evolution – Wiley Publishing: Weldrick, C.K., Trebilco, R., Davies, D.M., Swadling, K.M. Trophodynamics of Southern Ocean pteropods south of the Kerguelen Plateau. Ecology & Evolution. doi: 10.1002/ece3.5380 Christine K. Weldrick (70%) Dr. Kerrie M. Swadling (10%) Dr. Rowan Trebilco (10%) Dr. Diana M. Davies (10%) iv We the undersigned agree with the above stated “proportion of work undertaken” for each of the above published (or submitted) peer-reviewed manuscripts contributing to this thesis: Signed: Dr. Kerrie Swadling Primary Supervisor Institute for Marine & Antarctic Studies University of Tasmania Signed: Prof. Craig Johnson Head of Ecology & Biodiversity Centre Institute for Marine & Antarctic Studies University of Tasmania v Acknowledgements Unquestionably, the successful completion of this degree was largely due the continued support, dedication, and generosity in knowledge and with time of my supervisory team, Drs. Kerrie Swadling and Rowan Trebilco. For them, I am forever grateful. During my time at IMAS, my team presented me with multiple opportunities for personal and professional growth and experience. They have enabled me to hone my writing and analytical skills, and further develop my critical thinking. Important to also stress is the great patience they possess, as they gave me the right amount of pressure while I grappled with numerous mental and physical health obstacles in my personal life. Kerrie and Rowan have granted me other notable opportunities for upskilling, including those related to voyage preparation, problem solving, fieldwork logistics and international relations. Undeniably, my confidence surrounding my ability to even call myself a marine ecologist is attributed entirely to my team. I thank the organizations and institutes, including the Antarctic, Climate, & Ecosystems Cooperative Research Centre (ACE CRC), Australian Antarctic Division (AAD), Australian Nuclear Science and Technology Organization (ANSTO), Ecological Society of Australia (ESA), and Equity Trustees who provided opportunities and funding to enable the completion of this PhD research and research dissemination. There are a great number of other people who have assisted immensely in my PhD journey. To the captain, crew, fellow researchers/expeditioners, and science technical support aboard the RV Aurora Australis and TRV Umitaka-maru, thank you for safe passage over the Southern Ocean, keeping me positive, helping with sampling, and in some cases, keeping me company while I work up to 20 hours per day. There was a rescue mission involved, and I am truly grateful for the concerted effort of a large group of individuals to keep things from “going south” (pun intended). It was during this time that I forged an everlasting friendship with my true blue PhD pal, Jake Wallis, who shocks me every day with his capacity to put others before himself, and I owe him the moon for the many ways he’s helped me over the last few years. Ruth vi Eriksen and Kohei Matsuno, thank you so much for being sugoi travel mates and for introducing me to wonderful Japanese culture. Thank you Lavy Ratnarajah for giving your time to help me navigate the world of grant proposals. I have deep gratitude for Wenneke ten Hout, and her incredible ability to make all things possible. Of special note, I would be remiss if I failed to thank Felipe Briceño for letting me recover in his dreamy Puerto Varas home after catching something truly awful from the IsoEcol conference. Thanks to the anonymous examiners who dedicated their time and gave highly constructive feedback that greatly improved the quality of this work. There were other beings and entities that require mentioning here, particularly for their role in keeping my mental health floating above water: Karen Kilgariff and Georgia Hardstark of the My Favorite Murder podcast, the various networks that made all of the episodes of Terrace House, Twin Peaks, and Game of Thrones available for much needed decompression. Some of my more stressful moments were significantly eased by several furry and feathered beings, including Yeti, Tino, Bella, Millie, Wavy, Benti, Zaph, Rosie, Robin, Susie, Tommy, Finn, Frankie, Gingy Ninjy and Scamps (or whatever your real names are), and even you, too, Rocky and Peanut. But not you Pixie and Ziggy: you know what you did. Inevitably, this chapter of my life could not have been conceived if it weren’t for the tireless support of my life partner, Tom. From the deep, deep bottom of my heart, I am truly indebted to you. I have a million reasons to thank you, but I will always be grateful that you picked me for life. I’m excited to see what sort of adventures we’ll be getting ourselves into next. During my time as doctoral candidate, my grandmother, Hubert Barr, lost her battle with Alzheimer’s disease. She inspired me through her staunch leadership and community service through volunteerism. While I will always regret being so far away while she suffered. I’ve dedicated this work to her memory. This is for you, Nanny. vii viii General Abstract Southern Ocean (SO) thecosome pteropods are considered sentinels of anthropogenic ocean acidification (OA), and mounting evidence shows that rapid changes in ocean chemistry will affect their functional roles within marine ecosystems. However, there are major gaps in understanding of their current functional roles, along with the nature and magnitude of ongoing changes to these roles. There is urgency to address these gaps to establish a benchmark against which ongoing species-to-ecosystem scale responses may be assessed. The research in this thesis draws together state-of-the-art methodologies to provide new insights on the intra- and interspecific ecological roles of co-occurring SO pteropod species, focusing on the Indian sector of the Southern Ocean. In the first two data chapters of this thesis, I used analysis of tissue stable isotope signatures to derive new insights into trophodynamics of among 3 key species of Southern Ocean pteropods. In Chapter 2, I first used isotopic niche metrics and a