Patterns of Mercury Burden in the Seabird Community of Machias Seal Island, New Brunswick
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PATTERNS OF MERCURY BURDEN IN THE SEABIRD COMMUNITY OF MACHIAS SEAL ISLAND, NEW BRUNSWICK by Alexander Lyons Bond B.Sc., Mount Allison University, 2005 A Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of Master of Science in the Graduate Academic Unit of Biology Supervisor: A.W. Diamond Ph.D, ACWERN, Department of Biology & Faculty of Forestry and Environmental Management Examining Board: R.A. Curry, Ph.D, Department of Biology G.A. Benoy, Ph.D, Agriculture Canada and Environment Canada This thesis is accepted by the Dean of Graduate Studies THE UNIVERSITY OF NEW BRUNSWICK November 2007 © Alexander L. Bond, 2007 ABSTRACT The goal of this thesis was to examine the relationship between total mercury concentrations and stable isotopic ratios or carbon and nitrogen in a variety of tissues from seven breeding seabirds on Machias Seal Island (MSI), New Brunswick in 2005 and 2006. Trophic level, as indicated by 15N, was weakly correlated with total mercury concentration in most tissue-species combinations, suggesting other physiological or ecological factors influence mercury burden. MSI seabirds also had higher mercury levels than other studies of conspecifics. Northern Krill have higher mercury concentrations, and MSI seabirds have higher proportions of krill in their diet as compared to other sites. Of the six species examined, all were classified as ‘income’ breeders, using exogenous nutrients from the breeding grounds for egg production. Thus, mercury contamination from eggs collected on MSI represents local mercury acquisition rather than not long-distance transport. In a comparison of visual feeding observations to isotope mixing models, the visual study was more useful in estimating seabird diet because of uncertainty in the physiological factors affecting isotopic ratios. ii ACKNOWLEDGEMENTS First of all, I would like to thank Dr. Tony Diamond, my supervisor, for the great deal of encouragement and guidance that he provided me in the course of this project. From discussions in the field to long drives to meetings, I never ceased to learn from you. My supervisory committee members, Drs. S. Heard and R. Cunjak provided valuable guidance and encouragement. The wonderful folks in the SINLAB at UNB showed me all there is to know about stable isotopes, and my thanks go to Anne McGeachy, Christine Paton, Mireille Savoie, and especially Tim Jardine. In the mercury lab, I owe thanks to Dr. Paul Arp, Laura Jardine, Janet Otorowski and Dragana Perkman. While in the field, cold, wet days would have been much worse if it wasn’t for the lightkeepers (Barry, Gordon, Paul, Rick, Ralph and Russell). Warm suppers, stories and tunes made every day that much better. Thanks also go to the boat captains and crew, Peter, Durlan and Andy, for not only providing safe and sometimes exciting transportation to and from the island, but for friendship, mail deliveries, skiff rides, and treats from the mainland. My biggest appreciation is for those who helped in the field – Amie, Sara, Peter, Jennifer, Marie-Paule, Dorothy, Travis and Gabrielle – the days may have been long, but I could not imagine spending it with any other group of people. If any bird bit, scratched, defecated, vomited, or otherwise secreted something upon you in the course of my study, I would apologize, but that’s what birds do when poked and prodded. Other ACWERN lab-mates (André, Mathieu, Kate, Kevin, Emily, Laura, Ashley & Brad) and the folks that iii kept me organized in the Biology Office (Margaret, Rose, Marg and Marni) also deserve thanks for my various rants and requests. Finally, thanks to my family and Jeremy McGillan for putting up with my wayward tendencies, and for listening to my bird-related tirades. iv TABLE OF CONTENTS Abstract ......................................................................................................................ii Acknowledgements ....................................................................................................iii Table of Contents .......................................................................................................v List of Tables .............................................................................................................ix List of Figures ............................................................................................................xii List of Abbreviations .................................................................................................xiv Chapter 1: Introduction ..........................................................................................1 1.1 Seabirds as indicators of marine contamination ............................................2 1.2 Using stable isotopes to infer diet ..................................................................4 1.3 Focal species ..................................................................................................6 1.3.1 Family Alcidae ...................................................................................6 1.3.2. Family Laridae ...................................................................................7 1.3.3. Family Hydrobatidae .........................................................................7 1.3.4. Family Anatidae .................................................................................8 1.4 Hypotheses .....................................................................................................8 1.4.1 Hypotheses: Diet ................................................................................9 1.4.2 Hypotheses: Nutrient and contaminant allocation .............................9 1.5 Overview of chapters .....................................................................................10 1.6 Literature cited ...............................................................................................10 v Chapter 2: Mercury burdens in a seabird community from the Northwest Atlantic ........................................................................................................................17 2.1 Abstract ..........................................................................................................18 2.2 Introduction ....................................................................................................19 2.3 Methods..........................................................................................................23 2.3.1 Study site ............................................................................................23 2.3.2 Sample collection ...............................................................................24 2.3.3 Within-individual feather comparisons..............................................26 2.3.4 Stable isotope analysis .......................................................................26 2.3.5 Mercury analysis ................................................................................28 2.3.6 Statistical analysis ..............................................................................29 2.4 Results ............................................................................................................29 2.4.1 Mercury levels ...................................................................................29 2.4.2 Stable isotopes ...................................................................................33 2.5 Discussion ......................................................................................................35 2.5.1 Mercury levels in Machias Seal Island seabirds ................................35 2.5.2 Inferring diet: stable isotope analysis of Machias Seal Island seabirds ............................................................................................................38 2.5.3 Relationship between mercury and 15N ...........................................41 2.5.4 Nutrient allocation and implications for contaminant acquisition .....43 2.5.5 Mercury allocation in eggs.................................................................44 2.5.6 Comparison of MSI mercury levels to other studies .........................45 2.6 Conclusions and recommendations................................................................49 vi 2.7 Acknowledgements ........................................................................................50 2.8 Literature cited ...............................................................................................50 Chapter 3: Comparing adult and chick diet in two alcid species, the Atlantic Puffin Fratercula arctica and the Razorbill Alca torda, using stable isotope analysis ........................................................................................................................84 3.1 Abstract ..........................................................................................................85 3.2 Introduction ....................................................................................................86 3.3 Methods..........................................................................................................89 3.3.1 Study site ............................................................................................89 3.3.2 Chick provisioning .............................................................................90 3.3.3 Sample collection ...............................................................................90 3.3.4 Stable isotope analysis .......................................................................91