Carbonate chemistry and coral reefs in the Pacific coast of Costa Rica Dissertation with the aim of achieving a doctoral degree at the Faculty of Mathematics, Informatics and Natural Sciences Department of Earth Sciences at Universität Hamburg submitted by Celeste Sánchez Noguera from San José, Costa Rica Hamburg, 2019 Accepted as Dissertation at the Department of Earth Sciences Day of oral defense: 17.01.2020 Reviewers: Prof. Dr. Kay-Christian Emeis PD Dr. habil. Tim Rixen Chair of the Subject Doctoral Committee: Prof. Dr. Dirk Gajewski Dean of Faculty of MIN: Prof. Dr. Heinrich Graener To the memory of Dieter…. a beloved friend “Spread your wings and fly away, fly away, far away” - Queen CONTENTS Acknowledgements 1 Abstract 3 Zusammenfassung 4 List of publications 6 1. Scientific background 7 1.1. Carbonate chemistry and coral reefs …………………………………………………….. 7 1.2. Coral reefs from the Eastern Tropical Pacific ………………………………………... 9 1.3. Papagayo Upwelling System: a study location for ocean acidification scenarios ………………………………………………………………………………………………. 12 2. Objectives 13 3. Approach and outline of publications 14 4. Natural ocean acidification at Papagayo upwelling system (north Pacific Costa Rica): implications for reef development 17 4.1. Introduction ………………………………………………………………………………………….. 18 4.2. Methods ……………………………………………………………………………………………….. 19 4.3. Results ………………………………………………………………………………………………….. 24 4.4. Discussion …………………………………………………………………………………………….. 25 4.5. Conclusions ………………………………………………………………………………………….. 31 5. Carbonate chemistry gradient along the Pacific coast of Costa Rica influences reef development 33 5.1. Introduction ………………………………………………………………………………………….. 34 5.2. Materials and Methods …………………………………………………………………………. 35 5.3. Results ………………………………………………………………………………………………….. 39 5.4. Discussion …………………………………………………………………………………………….. 44 5.5. Conclusions …………………………………………………………………………………………… 49 5.6. Supplementary material ……………………………………………………………………….. 50 6. Rapid bioerosion in a tropical upwelling coral reef 56 6.1. Introduction ………………………………………………………………………………………….. 57 6.2. Materials and Methods …………………………………………………………………………. 59 6.3. Results ………………………………………………………………………………………………….. 63 6.4. Discussion …………………………………………………………………………………………….. 71 6.5. Conclusions …………………………………………………………………………………………… 76 6.6. Supplementary material ……………………………………………………………………….. 78 7. General discussion and conclusions 83 7.1. High local seawater variability in tropical coastal waters ……………………... 83 7.2. Can be the upwelling of Papagayo considered a real window to the future? ………………………………………………………………………………………………….. 84 7.3. Costa Rican coral reefs in the face of Climate Change and Ocean Acidification scenarios ………………………………………………………………………….. 86 8. Outlook and future research 88 List of figures 90 List of tables 95 References 97 Declaration in Lieu of Oath 118 ACKNOWLEDGEMENTS ACKNOWLEDGEMENTS Several people provided support and help during this academic journey. I would like to thank all those who, in one way or another, collaborated in the successful completion of my doctoral work. I would like to start with Dr. Tim Rixen, for the granted opportunity to work on this topic and carry out the project under his supervision. The conclusion of my thesis was possible thanks to his support and trust regardless of the distance. Also, would like to thank Prof. Dr. Kay-Christian Emeis, for the prompt review of my work and valuable comments, as well as his support during the doctoral procedure at the University of Hamburg. This research project was possible through the funding provided by the Leibniz Association. The Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) from Universidad de Costa Rica was a key partner in this academic collaboration during all the stages of the research project. I must thank to Ines Lange, with whom I built a deep underwater relationship during our joined fieldwork. Fieldwork would not have been possible without the important contribution of the following people and organizations: Minor Lara Víctor and family, Geovanny Bassey, Carlos Marenco, Marco and Alexis (captains), Fernando Monge and family, Jaime Nivia, Cristina Sánchez, José David “Pala” Palacios, Eleazar Ruíz, Oscar Montoya, Davis Morera, Lorena Guido, Emma Segura, Cuajiniquil Diving Center, Marina Papagayo, ScubaCaribe Diving Center, Rich Coast Diving, Gurrión Tour and Fundación Keto All laboratory analyses were possible with the help of colleagues and technicians from Germany and Costa Rica: Dieter Peterke, Dorothee Dasbach, Matthias Birkicht, Christina Staschok, Achim Meyer, Epiphane Yéyi, Jenaro Acuña, Juan Guillermo Sagot and Adrián Pinto. Through all these years I have had meaningful guidance, both in scientific and personal matters, from Carlos and Chrystalla, don Jorge, Chepe and don Álvaro. I am also deeply grateful to Anita and Esteban, not only for constant guidance and productive discussions (not restricted to science) but also for their honest friendship. My PhD-life was splitted between Germany and Costa Rica and this was definitively a precious gift. I was lucky enough to have academic collaboration between two countries and two amazing research institutions (Leibniz Centre for Tropical Tropical Marine Research and CIMAR), but also for counting with two networks of friends who provided personal support in two different continents. Thanks to the “girls around the world” (Francisca, Astrid, Ale, Maryam, Mariana and Swati) for uncountable tea/hot chocolate breaks and other adventures in Germany. Gaby Webber and Danny for our “Friday’s tradition”, Balbina and Nati for being there for academic and personal business. Bremen became a second home thanks to Gaby Boehme, Dieter and Barbara, Esteban and Gaby Alfaro. I am also grateful for my close CIMAR-family (Chepe, Cindy, 1 ACKNOWLEDGEMENTS Eddy, Jeffrey, Juanca and don Gerardo), for holding me up way beyond academia. Moreover, in the last years of this academic ride I have met amazing people from all around the world and I am deeply thankful to all those who cheered me up in the very last phase of my thesis. I thank Eric for all the emotional (and technological) support he represented during the first part of this journey. And last but not least, a huge and special acknowledgement to my mom for her unconditional support through the whole doctoral process. 2 ABSTRACT ABSTRACT Coral reefs are important tropical ecosystems holding about 25% of the world marine biodiversity. Their tridimensional biogenic structures are built of calcium carbonate and they are threatened by global warming and ocean acidification. Current projections on the future development of coral reefs suffer among others from the scarcity of local observations, especially along the Costa Rican coast in the Eastern Tropical Pacific (ETP). The aim of this thesis was to investigate the carbonate chemistry in coastal waters and their effect on the reef development along this coast. It reveals a strong gradient from reefs influenced by upwelling in the north towards reefs affected by river discharges in the south. Due to this gradient we selected three study sites: Santa Elena in the north, Marino Ballena in the south and Matapalo between these two sites. Parameters required to determine the carbonate system (pH, pCO2, TA and DIC) including temperature, salinity and nutrients were measured during the dry and rainy season. Furthermore, the benthic composition was quantified by reef surveys and in situ studies were carried out to identify the effect of local environmental variables on reef organisms. Our results evidenced that coastal upwelling and metabolic reactions (photosynthesis and respiration) are the main drivers in the north (Santa Elena), whereas calcification and carbonate dissolution in addition to river discharges exert a strong control on the carbonate chemistry in the south (Marino Ballena). The dominant coral species in the south (Porites lobata and Pavona clavus) cope with enhanced suspended matter concentrations, a low salinity, and a low aragonite saturation state (Ωa). Reef-builders in the north (Pavona gigantea, Pavona clavus and Pocillopora sp.) are also tolerant to low Ωa but are adapted to low sea water temperatures and euthrophic conditions. However, enhanced nutrient inputs into reefs enhance productivity, which in turn favors the growth of larger and more effective benthic bioeroders. In addition to strong currents, this enhances erosion and explains the low reef accretion rates in the ETP compared to the Western Tropical Pacific. The progressing ocean acidification, changes in the strength of upwelling and enhanced inputs from land threaten the sensible balance between reef accretion and erosion along the Costa Rican coast. In the future these processes and their combined impact on reefs need to be monitored and studied in more detail, in order to find ways to better protect these coral reefs. 3 ZUSAMMENFASSUNG ZUSAMMENFASSUNG Korallenriffe sind wichtige tropische Ökosysteme, die ca. 25% aller bekannten und im Ozean vorkommenden Arten beherbergen. Sie bilden dreidimensionale biogene Strukturen, die im wesentlichen aus Kalziumkarbonat bestehen. Die globale Erwärmung und die Versauerung der Ozeane bedrohen das Wachstum der Korallen und somit auch den Bestand der Riffe. Direkte Beobachtungen, die die Reaktionen von Riffen auf globale Veränderungen beschreiben, sind jedoch bisher selten und fehlen zur Validierung von Modellen, die die zukünftige Entwicklung von Korallenriffen vorhersagen. Das Ziel dieser Arbeit war es, die