ISBN 9789082561135 Cover design and layout: Lisa Mevenkamp Cover illustration: Ee Zin Ong Printed by : Reproduct nv Voskenslaan 205 9000 Gent Marine Biology Research Group Campus Sterre – S8 Krijgslaan 281 9000 Gent Marine Biology & Ecology Research Centre Plymouth University Plymouth PL4 8AA UK Academic year 2018 – 2019 Publically defended on September 26th, 2018 For citation to published work reprinted in this thesis, please refer to the original publications. Ong, E.Z. (2018). Behavioural and ecophysiological responses of marine benthos to ocean acidification and warming. Ghent University, 250pp Behavioural and ecophysiological responses of marine benthos to ocean acidification and warming Ee Zin Ong Student number: 01410807 Supervisor(s): Dr. Carl Van Colen, Prof. Dr. Tom Moens, Prof. Dr. Mark Briffa A dissertation submitted to Ghent University and Plymouth Univeristy in partial fulfillment of the requirements for the degree of Doctor of Science: Marine Sciences Academic year: 2018 – 2019 SUPERVISORS: Dr. Carl Van Colen Prof. Dr. Tom Moens Prof. Dr. Mark Briffa MEMBERS OF THE EXAMINATION COMMITTEE Prof. Dr. Ann Vanreusel – Ghent University (Chairman) Dr. Ulrike Braeckman – Ghent University (Secretary) Dr. Michael Thom – Plymouth University Prof. Dr. Sam Dupont – Gothenburg University Prof. Dr. Jan Vanaverbeke – Royal Belgian Institute of Natural Sciences (RBINS), Visiting professor Ghent University Dr. Carl Van Colen * – Ghent University Prof. Dr. Tom Moens* – Ghent University Prof. Dr. Mark Briffa * – Plymouth University *Non-voting member FIANCIAL SUPPORT This work was co-funded through a MARES Grant (2012-1720/ 001-001-EMJD). MARES is a Joint Doctorate program selected under Erasmus Mundus coordinated by Ghent University (FPA 2011e0016). Additional funding for this research was obtained from the Special Research Fund (BOF) from UGent through GOA project “Assessing the biological capacity of ecosystem resilience” (grant n°: BOFGOA2017000601). Experimental facilities were provided by EMBRC Belgium - FWO project n° GOH3817N. Climate change is one of those things that everyone seems to have an opinion about, but few people understand. Thom Hartmann The Last Hours of Ancient Sunlight Contents Acknowledgements ........................................... I Samenvatting ............................................... VII Summary ................................................... XVII Chapter 1 ........................................................ 1 1.1 Atmospheric carbon increase ...................4 1.1.1 Ocean acidification ............................ 5 1.1.2 Ocean warming ............................... 10 1.2 Evil twins: Global warming and ocean acidification ................................................. 12 1.3 Bivalves .............................................. 18 1.3.1 Ecological and economical importance of bivalves .................................................. 22 1.3.2 How do marine bivalves cope with environmental change? ............................. 26 1.3.3 Study species ................................. 30 1.4 Environments ...................................... 34 1.4.1 Oosterschelde ................................ 35 1.4.2 Westerschelde ................................ 38 1.5 Outline and objective of the thesis ......... 40 Chapter 2 ...................................................... 45 2.1 Abstract .............................................. 47 2.2 Introduction ........................................ 48 2.3 Material and methods ........................... 53 2.3.1 Collection and incubation of cockles .. 53 2.3.2 Cockle condition and physiology ....... 57 2.3.3 Statistical analysis .......................... 61 2.4 Results ............................................... 62 2.5 Discussion ........................................... 68 2.6 Acknowledgments ................................ 75 2.7 Appendices ......................................... 76 Chapter 3 ...................................................... 81 3.1 Abstract .............................................. 83 3.2 Introduction ........................................ 85 3.3 Material and methods ........................... 89 3.3.1 Collection and incubation of Scrobicularia plana ……………………………………………………………89 3.3.2 Hydraulic activity measurements and behavioural identification .......................... 93 3.3.3 Scrobicularia plana condition index and abiotic sediment properties ....................... 97 3.3.4 Statistical analysis ........................... 98 3.4 Results .............................................. 101 3.4.1 Behavioural observations ............... 101 3.4.2 pH sediment profile ....................... 102 3.4.3 Sediment organic matter and pigment concentration ........................................ 103 3.4.4 Conditional and behavioural responses ............................................. 104 3.5 Discussion ......................................... 108 3.6 Acknowledgements ............................. 113 3.7 Appendices ....................................... 114 Chapter 4 .....................................................119 4.1 Abstract ............................................ 121 4.2 Introduction ...................................... 123 4.3 Material and methods ......................... 129 4.3.1 Collection of sediment and specimens .............................................129 4.3.2 Experimental set-up .......................130 4.3.3 Sediment abiotic properties .............134 4.3.4 Oxygen and nutrient fluxes .............135 4.3.5 Macrofauna ...................................137 4.3.6 Statistical data analysis ..................137 4.4 Results ............................................. 139 4.4.1 Manipulation of temperature and pHT...... ...................................................139 4.4.2 Effects on sediment abiotic properties ..............................................139 4.4.3 Effects on oxygen and nutrient fluxes ………………………………………………………….140 4.4.4 Effects on macrofauna ................... 141 4.5 Discussion ......................................... 145 4.6 Acknowledgements ............................. 152 4.7 Appendices ........................................ 153 Chapter 5 .................................................... 161 5.1 Good practices for ocean acidification and warming research ...................................... 166 5.1.1 Ecological relevance and interpretability of the experimental approaches ............... 167 5.1.2 Different spatio-temporal scales ...... 169 5.1.3 The need to avoid pseudoreplication 173 5.1.4 Accuracy of laboratory setting and measurements ....................................... 175 5.2 The need for insights at different levels of biological organisation ................................ 177 5.3 Impacts of acidification and warming on bivalve populations fitness .......................... 186 5.4 Interaction of acidification and warming with other environmental changes ...................... 189 5.4.1 Host and parasites interactions ........190 5.4.2 Food availability.............................193 5.5 Future research directions ................... 194 Appendix .....................................................201 A.1 Material and methods ........................... 203 A.1.1 Collection and incubation of specimen ...............................................203 A.1.2 Spawning induction of bivalves ........206 A.1.3 Statistical analysis ..........................207 A.2 Results ............................................... 209 Cited literature .............................................213 Acknowledgements How to start the acknowledgement after a 4-years long crazy and amazing adventure?! This particular book, would not be possible without the help of many incredible people who came across my path. I am lucky enough to have had Carl as my mentor along this journey. I really enjoyed our brainstorming sessions, field works we have done together and other crazy adventures e.g. being chased by cattle in the field, the trip to Spain and Portugal with delicious food and being guided by an outdated GPS. I would not have done it without your endless patience, support, guidance and encouragement during my PhD. Your challenges have pushed me outside of my comfort zone where I have learned and developed. It is a great pleasure to work with you and I thank you for everything. Tom, I sincerely thank you for the wisdom, encouragement and opportunity that you have given me during my PhD. You have been very supportive and always open to new ideas. It has been reassuring to have you to around especially throughout the final stages of my PhD. I would like to express my gratitude to Mark. You have been supportive and accommodating all along the way. You have arranged for a joyful stay in Plymouth and introduced me to good friends and colleagues such as Mariana and Sarah. I would like to thank all the members of the examination committee (Dr. Ulrike Braeckman, Dr. Michael Thom, Prof Dr. Jan Vanaverbeke, Prof. Dr. Sam Dupont and Prof. Dr. Ann Vanreusel) for their valuable time and constructive suggestions and comments that helped to considerably improve the quality of the thesis. III In what follows I wish the mention all the colleagues that have added beautiful colour to this journey. First of all, special thanks to Yves and Dirk, who constantly borrowed me “their brain” to solve problems. My sincerest gratitude to Annick, Guy, Bart, Annelien, Bruno, Niels and Ilsa for their support in the lab and field. I have learned a lot from