Ancient Clam Gardens Magnify Bivalve Production by Moderating Ambient Temperature and Enhancing Sediment Carbonate
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Ancient clam gardens magnify bivalve production by moderating ambient temperature and enhancing sediment carbonate by Natasha Salter B.Sc., McGill University, 2013 Report No. 709 Project Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Resource Management in the School of Resource and Environmental Management Faculty of Environment © Natasha Salter 2018 SIMON FRASER UNIVERSITY Summer 2018 Copyright in this work rests with the author. Please ensure that any reproduction or re-use is done in accordance with the relevant national copyright legislation. Approval Name: Natasha Salter Degree: Master of Resource Management Report No: 709 Ancient clam gardens magnify bivalve production Title: by moderating ambient temperature and enhancing sediment carbonate Examining Committee: Chair: Erin Slade MRM candidate Anne Salomon Senior Supervisor Associate Professor Kirsten Rowell Supervisor Director of Research Leadership Research and Innovations Office Colorado University Date Defended/Approved: August 27, 2018 ii Abstract Humans have been developing management systems to support resilient food production through social-ecological feedbacks for millennia. On the Northwest Coast of North America, Indigenous peoples have sustained a diversity of fisheries through management innovations including designated access rights, harvest restrictions, and enhancement strategies. To elucidate how clam gardens, intertidal rock-walled terraces constructed by people in the Late Holocene, increased bivalve production, we quantified environmental variables and transplanted clams (Leukoma staminea) in present-day clam gardens and non-walled control beaches on the coast of western Canada. We found that higher bivalve biomass and densities in clam gardens could be attributed to the effect of terracing on ambient temperature and elevated sediment carbonate associated with crushed shell. These same variables drove detectable differences in transplanted clam growth rates. This study illuminates ecological mechanisms underlying this ancient innovation that could be used to enhance food security and confer resilience to impending oceanic changes. Keywords: clam gardens; bivalves; mariculture; Indigenous peoples; Indigenous ecological knowledge; calcium carbonate iii Acknowledgements I would like to acknowledge and express my gratitude for living, learning, working and playing in the unceded traditional territories of the sḵwx̱ wú7mesh (Squamish), sel̓íl̓witulh (Tsleil Waututh), Stó:lō (Sto:lo), and xʷməθkʷəy̓ əm (Musqueam) Nations during my graduate studies at Simon Fraser University. My research was conducted on Quadra Island which lies within the unceded territories of the Northern Coast Salish & the Southern Kwakwaka’wakw First Nations. I would like to express gratitude for the support of the Laich-Kwil-Taich Treaty Society in carrying out this work. I would also like to recognize and express gratitude to the many people who have come before me who have generated, carefully protected, and generously shared their knowledge. As a white settler it is integral that I acknowledge my privilege to access these spaces and bodies of knowledge. I’m incredibly grateful to the people who have an intimate knowledge of the seascapes and landscapes where I conducted my research and the many generations of ancestors that came before them. Specifically, the late Kwaxsistalla who shared knowledge and opened the hearts and minds of so many to the existence of clam gardens and the many ways that spaces in the Pacific Northwest have been transformed and cared for. Also, the Gulf Hul’qumi’num Treaty Group for compiling, documenting, and making knowledge accessible. Although I did not have the opportunity to work with these communities, I am grateful and humbled to study in these ecocultural systems that Indigenous peoples have cared for and managed for millennia. I would like to thank my supervisors Anne Salomon and Kirsten Rowell for their guidance, support and wisdom. Aspects of this project were a leap of faith; you gave me the opportunity to try something new, accepting I might fail. I could not have asked for a better gift. This project was truly a labour of love. Thank you to the many students and friends who volunteered their time in field: Mareike Babuder, Kayla Balmer, Saira Butter, Kirsten Calder-Sutt, Jeff Lemon, Duncan MacLennan, Mikayla More O'Ferrall, and Nicola Rammell. To Amy Groesbeck, thank you for your leadership and helping me become more confident in my work. To Laura Gray, for laughter and encouragement. To Chris Roberts, thank you for your patience, insights and care, and to Louie Wilson, thank iv you for your patience as I learned the ropes and for the many adventures, and to both for generously sharing your knowledge. To Morgan Black, thank you for teaching me to operate with ease and grace in field. To my mum, Susan Still, and old friend, Anna Rotman, thank you for joining me in the field. Having you both witness and take part is this process was extremely validating. The design and methods for this project benefitted from the insights of so many: Sarah Dudas, Rhea Smith, Marco Hatch, Mark Green, Daphne Munroe, Leah Bendell, Bridget Doyle, Karen Kohfeld, Ellie Simpson, Helen Gurney-Smith, Mark Henry (MHE products), Martin Koelling, and George Waldbusser. Thank you for taking the time to answer emails from afar or meet with me. To Marty Davelaar, thank you for taking a chance on teaching an ecologist biogeochemistry. To Ben Hudson, thank you for your endless generosity. And many thanks to Chris Harley, Karen Kohfeld, and their students for use of equipment and lab space. I would also like to thank Dana Lepofsky, Chris Roberts, Louie Wilson, Ginevra Toniello, and Travis Crowell for many archaeological insights and more. Thank you to the staff of the School of Resource and Environmental Managmenet and the Hakai Institute for logistical support and endless kindnesses. I would also like to express gratitude for funding from the Tula Foundation, Natural Sciences and Engineering Research Council of Canada, and the Chad Day Fellowship in Resource Management. Finally, I would like to express gratitude to the many people who made this journey brighter. To my lab mates in the Coastal Marine Ecology and Conservation Lab – Carolyn Prentice, Markus Thompson, Gabby Pang, Jenn Burt, Skye Augustine, Hannah Kobluk, Erin Slade, Sachiko Ouchi, and Lynn Lee – you are all incredible such ecologists and supportive friends. Every day, I felt that I was part of a team with all of you rallying around me. To REMfam, your friendships sustained me. To Carolyn Prentice and Chloe Boyle for all the love and adventures, and to Jon Boron, you have been my rock (and who knew you would be such an excellent field assistant!). To my family, for all your love, support and patience. To Erin de Sousa, for never pushing, but always knowing I would get here. v Table of Contents Approval .......................................................................................................................... ii Abstract .......................................................................................................................... iii Acknowledgements ........................................................................................................ iv Table of Contents ........................................................................................................... vi List of Figures ................................................................................................................vii Image ............................................................................................................................. ix Introduction ................................................................................................................... 1 Methods ......................................................................................................................... 4 Study Area ...................................................................................................................... 4 Clam Surveys .................................................................................................................. 4 Clam Transplant Experiment ........................................................................................... 5 Environmental Variables ................................................................................................. 5 Statistical Analyses ......................................................................................................... 7 Assumptions and Limitations ........................................................................................... 9 Results ......................................................................................................................... 10 Clam Surveys ................................................................................................................ 10 Clam Transplant Experiment ......................................................................................... 11 Discussion ................................................................................................................... 13 Environmental Variables Affecting Clam Density, Biomass, and Growth ....................... 13 Clam Garden Ecology in an Ever-Changing Human-Enhanced Seascape .................... 19 Buffering Capacity of Clam Gardens Fosters Resilience and Enhances Food Security . 21 Conclusion .................................................................................................................