Seagrass macrophytodetritus: a copepod hub - Species diversity, dynamics and trophic ecology of the meiofauna community in Posidonia oceanica leaf litter accumulations University of Liège Faculty of Sciences Department of Biology, Ecology and Evolution Laboratory of Oceanology, MARE centre & Ghent University Faculty of Sciences Department of Biology Marine Biology research group Academic year 2014-2015 Publically defended on 10/6/2015 For citation to the published work reprinted in this thesis, please refer to the original publications (as mentioned at the beginning of each chapter). To refer to this thesis, please cite as: Mascart T., 2015. Seagrass macrophytodetritus: a copepod hub - Species diversity, dynamics and trophic ecology of the meiofauna community in Posidonia oceanica leaf litter accumulations. University of Liège/Ghent University, 256 pp. Front cover: Microscopic pictures of harpacticoid copepods. From top to bottom: Alteutha depressa, Phyllopodopsyllus bradyi, Paralaophonte brevirostris, Longipedia minor, Tegastes falcatus, Porcellidium ovatum, Laophontodes bicornis and Laophonte cornuta. Back cover: Underwater photography of a macrophytodetritus accumulation on a sand patch adjacent to a Posidonia oceanica meadow, Calvi, Corsica. Photographs back cover and between chapters: Courtesy of underwater photographer Arnaud Abadie Members of the examination committee Members of the reading committee* Prof. Dr. Bernard Tychon – Chairman ULg University of Liège, Belgium Prof. Dr. Tom Moens – Chairman UGent Ghent University, Belgium Prof. Dr. Patrick Dauby University of Liège, Belgium Prof. Dr. Magda Vincx Ghent University, Belgium Dr. Salvatrice Vizzini * Università degli Studi di Palermo, Italy Dr. Corine Pelaprat Stareso S.A., France Dr. Loïc Michel * University of Liège, Belgium Dr. Carl Van Colen * Ghent University, Belgium Dr. Gilles Lepoint – Promotor University of Liège, Belgium Prof. Dr. Marleen De Troch - Promotor Ghent University, Belgium Seagrass macrophytodetritus: a copepod hub - Species diversity, dynamics and trophic ecology of the meiofauna community in Posidonia oceanica leaf litter accumulations Thibaud Mascart Promoters: Dr. Gilles Lepoint (ULg) Prof. Dr. Marleen De Troch (UGent) Academic year 2014-2015 Thesis submitted in partial fulfilment of the joint PhD degree of Doctor of Science (Environmental Sciences and Management) awarded by the University of Liège (Marine Sciences) awarded by the University of Ghent En mémoire de maman, car baisser les bras n’est jamais une option. Acknowledgements iii Summary vi Résumé ix Samenvatting xii List of abbreviations xv CHAPTER 1 General introduction 1. PREFACE AND RESEARCH FRAMEWORK 1 2. SEAGRASS ECOSYSTEMS 5 3. POSIDONIA OCEANICA ECOSYSTEM 6 4. MACROPHYTODETRITUS DECOMPOSITION REGULATORS 11 5. MEIOFAUNA AND COPEPODA 16 6. HARPACTICOID COPEPODS IN FOOD WEBS STUDIES 20 7. PHD OUTLINE 22 8. RESEARCH OBJECTIVES 25 CHAPTER 2 Sampling locations and sampling processes 1. STUDY SITE DESCRIPTION 27 2. SAMPLE COLLECTION AND TREATMENT 49 CHAPTER 3 45 Seasonal variability of macrophytodetritus, meiofauna and copepod community CHAPTER 4 79 Inter-annual variation of the macrophytodetritus and associated meiofaunal and copepod communities CHAPTER 5 95 Copepod feeding ecology and niche width: insights from stable isotopes and fatty acids CHAPTER 6 133 How do harpacticoid copepods colonize detrital seagrass leaves? i CHAPTER 7 General discussion, novel findings and future considerations 1. MACROPHYTODETRITUS AS FEEDING GROUNDS 163 2. MEIOFAUNA COMMUNITIES IN MACROPHYTODETRITUS 169 3. ECOSYSTEM FUNCTIONING AND TROPHIC INTERACTIONS IN THE MACROPHYTODETRITUS HABITAT 174 4. GENERAL CONCLUSION 182 5. NOVEL FINDINGS 184 6. FUTURE CONSIDERATIONS 185 Addendum I 187 Addendum II 189 Addendum III 192 Addendum IV 194 Publication list 217 Cited literature 220 ii Acknowledgements Acknowledgements This dissertation is not only the result of what I achieved during the last four years, it is foremost the copious quantities of assistance in all manner of things, from great ideas, motivations, questions, energy, laughter and discussions to a simple ‘why don’t you try that?’. This could not have been possible without the help and support of many of you! First and foremost, allow me to thank my promotor tandem! Marleen and Gilles, thank you for all the advice (work related and not work related) I got during those years. Thank you for sharing your passion and for always having your doors open for a constructive discussion. Thank you, for your different points of view and methodologies. Thank you, for your guidance, availability and perseverance. Hereby, my upright appreciation for both of you! I had the chance to work in two laboratories and to witness the appointment of two new head of laboratories. Therefore, thank you Magda Vincx and Jean-Marie Bouquegneau for welcoming me in your labs and making me feel like at home. Ann Vanreusel and Sylvie Gobert, thank you for the liberty you gave me to follow my passion in research and I wish you both good luck in following yours. Studying very small organisms, setting up things in the sea, working with complex equipment is not possible without many enthusiastic helping hands. Thank you Annick, for the uncountable microscopic slides of copepods; Guy, for efficiently counting and identifying meiofauna; Niels, for washing that horrible “fluff” in my samples; Isolde, for dealing with that joint-venture complexity; Dirk, for extracting fatty acids and analyses of those very small peaks; Silke and Laura, for holding on during the identifications of those cute little copepods during your master theses; iii Acknowledgements Françoise, merci d’avoir répondu à mes nombreux coups de fils urgents concernant des bons de commande oubliés et finalement Renzo, merci pour tes fabrications ingénieuses ainsi que ton aide incontestable pour le design expérimental. I am extremely grateful to the ‘models and statistics hotline’, Jan Vanaverbeke, Nicolas Sturaro, Ulrike Braeckman, Loïc Michel and Carl Van Colen for shedding the light on some complex stuff and making it look like you eat it for breakfast. I really enjoyed our conversations and brainstorming. Chers Staresiens, merci de m’avoir accueilli en Corse comme un membre de la famille et de m’avoir aidé à vider la baie de litière ainsi que pour toutes les bières de décompression après nos longues plongées et journées passé à tamiser. Merci en particulier à Pierre, Coco, Alex, Sylvain, Richard, Nilu et Aurélia d’avoir toujours été là, ainsi qu’à tous les autres avec qui j’ai pu partager les couchers de soleil sur la Baie de Calvi. Of course research is not possible without funding. Therefore I would like to show my gratitude to the Fonds national de la recherche scientifique (bourse FRIA) for my grant as well as the University of Liège for a bourse du Patrimoine. I take the opportunity to specially thank the assessment and reading committees for their precious comments and criticism given along the pathway of the deposition of this thesis: Prof. Dr. Bernard Tychon, Dr. Corinne Pelaprat, Dr. Carl Van Colen, Dr. Gilles Lepoint, Dr. Loïc Michel, Prof. Dr. Marleen De Troch, Prof. Dr. Magda Vincx, Prof. Dr. Patrick Dauby, Dr. Salvatrice Vizzini and Prof. Dr. Tom Moens. I was so lucky to enjoy working in three very different places with colleagues from ‘le laboratoire d’océanologie’, ‘de marine biologie’ and ‘la Stareso’. Everyone present deserves an enormous thank you for making the coffee breaks, lunch breaks, after lunch walks, conferences, walks to the lighthouse, hallway chitchat, Friday drinks and department outgoings so iv Acknowledgements enjoyable. I hope someday will come we come across each other once again. I would like to thank two PhD-buddies in particular. Freija, we zijn samen begonnen in de biologie en sindsdien zijn onze wegen samen gebleven. Bedankt voor je eindeloze steun doorheen de roller coaster dat het leven is. Bedankt om altijd klaar te staan om een vélootje te drinken net voordat je je trein moest nemen naar A’pen. François, mon compagnon de palanqué. Depuis nos échantillonnages, je ne pars plus jamais sans un rouleau de duct tape et une poignée de colsons en poche. Merci pour les heures passées ensemble sous l’eau, sur l’eau, sur la route, devant, au-dessus et en-dessous de l’IRMS (qui a failli à maintes reprises valser par la fenêtre). Merci, pour nos innombrables échanges d’idées et discussions variés. I wish you both, all the best for your upcoming defence! Finally, I wish to thank my friends from the bottom of my heart and foremost my wife, Kamila. Thank you for your patience and being by my side. I cannot express how much your support and love has meant to me over these years. Bardzo dziękuję, kocham cię do gwiazd i jeszsze dalej! En dernier, merci papa pour ton support continu durant toutes ces années. Merci de m’avoir appris à faire avec les moyens du bord et de ne jamais baisser les bras. Sans toi je ne serais pas arrivée ou je me trouve aujourd’hui. And as a really final acknowledgment, I would like to thank the Belgian kingdom. Even though your administration doesn’t make it easy for interregional exchange, I witnessed both sides of the “language border” and I am proud to say that working together is not so bad at all. On the contrary, the confluence of different backgrounds only makes the mixture more dynamic and richer! I sincerely hope more joint ventures will see the light in a near future. v Summary Summary Macrophytodetritus is a heterogeneous mixture of detrital material that accumulates