CASCADING EFFECTS OF PREDATORS IN TEMPERATE AND SUBTROPICAL SHALLOW LAKES Carlos Iglesias PhD Thesis 2010 NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE AU AARHUS UNIVERSITY FACULTY OF SCIENCE AU AARHUS UNIVERSITY CASCADING EFFECTS OF PREDATORS IN TEMPERATE AND SUBTROPICAL SHALLOW LAKES PhD Thesis 2010 Carlos Iglesias NATIONAL ENVIRONMENTAL RESEARCH INSTITUTE FACULTY OF SCIENCE AU AARHUS UNIVERSITY AU AARHUS UNIVERSITY Data sheet Title.: Cascading effects of predators in temperate and subtropical shallow lakes Subtitle: PhD thesis Author: Carlos Iglesias Departments: Department of Freshwater Ecology, National Environmental Research Institute (NERI), Aarhus University Department of Biological Sciences, Faculty of Sciences, Aarhus University Publisher: National Environmental Research Institute© Aarhus University – Denmark URL: http://www.neri.dk Year of publication: December 2010 Accepted for public defence: November 2010 Associate Professor Birgit Olesen, Aarhus University (Chairman of the Committee) Professor Lars-Anders Hansson, University of Lund, Sweden Associate Professor Frede Østergaard Andersen, University of Southern Denmark Supervisors: Professor Erik Jeppesen, Department of Freshwater Ecology, National Environmental Research Institute, Aarhus University Professor Hans Brix, Department of Biological Sciences, Aarhus University Associate Professor Néstor Mazzeo, Universidad de la República, Uruguay Associate Professor Mariana Meerhoff, Universidad de la República, Uruguay Financial support: Danish Agency for Science, Technology and Innovation, Ministry of Science, Technology and Innovation Please cite as: Iglesias, C. 2010: Cascading effects of predators in temperate and subtropical shallow lakes. PhD thesis. Dept. of Freshwater Ecology, NERI and Dept. of Biological Sciences, Faculty of Sci- ences Aarhus University. National Environmental Research Institute, Aarhus University. 131 pp. http://www.dmu.dk/Pub/PHD_CIG.pdf Reproduction permitted provided the source is explicitly acknowledged Abstract: With a climate warming perspective, the present thesis aimed to compare the functioning of shallow lakes in contrasting climate zones by conducting a series of fi eld mesocosm experi- ments and fi eld surveys of the food web structure and trophic interactions in lakes located in subtropical Uruguay and temperate Denmark. The structuring role of fi sh was proven experi- mentally in both climate regions, with strong cascading effects on the pelagic food webs and particularly so in the subtropics. Together with higher fi sh diversity, trophic webs in warmer lakes were generally one trophic level shorter than their temperate counterparts. We argue that the widespread omnivory of fi sh across the food web explains the shorter food webs and the weakness of cascading effects, seldom reaching phytoplankton, in real lakes in the subtropics, thus having profound effects on ecosystem functioning. The complexity of trophic interactions in warmer systems may therefore weaken important positive feedback mechanisms, known from temperate lakes, and thereby decrease the stability and resilience of the clear water state. The evidence from subtropical lakes may, with caution, provide indications of the responses to be expected with warming in currently cold ecosystems. Keywords: Climate warming, shallow lakes, fi sh structuring role, subtropical lakes, trophic interactions, trophic web structure Layout and drawings: NERI Graphics Group, Silkeborg Front page: Fish series, Ceramics by Natalia Barberán. Photo: Carlos Iglesias ISBN: 978-87-7073-196-6 Number of pages: 131 Internet version: The report is available in electronic format (pdf) at NERI’s website http://www.dmu.dk/Pub/PHD_CIG.pdf Content Acknowledgements 5 List of included papers 6 1 Summary 7 Dansk resumé 9 2 Introduction 11 2.1 The role of predation in shallow lake food webs under different climates 11 2.2 Potential implications in a climate warming scenario 12 3 Research approach and questions 14 4 The structuring role of fi sh and cascading effects in the littoral and the pelagic food webs 15 5 Food web architecture in subtropical and temperate shallow lakes 24 6 Conclusions and Perspectives 30 7 References 32 Paper 1 39 High predation is the key factor for dominance of small-bodied zooplankton in warm lakes - evidence from lakes, fi sh exclosures and surface sediment. Paper 2 59 Field and experimental evidence of the effect of Jenynsia multidentata Jenyns (Cyprinodontiformes, Anablepidae) on the size distribution of zooplankton in subtropical lakes. Paper 3 71 Cascading effects promoted by fi sh and macroinvertebrates on food webs of shallow lakes in different climate zones – a mesocosm experiment Paper 4 89 Trophic cascade effects of Hoplias malabaricus (Characiformes, Erythrinidae) in subtropical lakes foodwebs: a mesocosm approach Paper 5 101 Fish community seasonal and diel variation in four subtropical shallow lakes with different water transparency (southern Uruguay) Paper 6 115 Food webs are more truncated in subtropical than temperate shallow lakes: Implications of fi sh omnivory in warm lakes “My momma always said, life was like a box of chocolates. You never know what you're gonna get." Forrest Gump Acknowledgements Today when I look back I see myself lost with no clear perspectives, but my chocolate box still holds some chocolates and even some of the best. My family was always there for me – my parents, my brother and my sis- ter. Natalia, my dear wife, encouraged me to go back to biology; her cour- age and power were really motivating to me. She also gave me 3 children who are the reason for my breathing. I dedicate this thesis to all of them. I would like to thank my supervisors, Hans Brix and Erik Jeppesen, and my co-supervisors in Uruguay, Néstor Mazzeo and Mariana Meerhoff, for their guidance and friendship during this project. I would also like to thank all the people from NERI, especially the “shallow lakers”, all the members of the freshwater ecology group who helped me tremendously during my stay in Denmark: Susanne Amsinck, David Balayla, Sandra Brucet, Teresa Buchaca, Lissa S. Hansen, Karina Jensen, Liselotte S. Jo- hansson, Thomas B. Kristensen, Frank Landkildehus, Torben L. Laurid- sen, Lone Liboriussen, Louise Nathansen, Lisbet Sortkjær, Martin Sønder- gaard, Kirsten Landkildehus Thomsen, Tommy Silberg and Marc Ventura. I still miss the Monday afternoon coffee break and the incredible working atmosphere you had at NERI. I greatly appreciate the kind help Anne Mette Poulsen gave me with the editing of papers and the thesis itself, but particularly because she was always there to help me with all kinds of practical issues of day-to-day family life. I acknowledge also the support I received in many aspects during this period from Research Director Kurt Nielsen. Erling Pedersen and Frankie Zea Henriksen offered me effective solutions to my practical and technological problems. Tinna Christensen did a great job – fi gures and layout look nice thanks to her. Thanks go also to my friends and col- leagues in Uruguay who were always ready to help. I am deeply thankful to all who enthusiastically helped me with the exten- sive fi eld work, without their help this thesis could not have been made: Eti Levi, Frank Landkildehus, Kirsten Landkildehus Thomsen, Torben L. Lauridsen, Tommy Silberg, Klaire Houeix, Lúcia Lobão, Marcelo Guer- rieri, Nihan Yazgan, Ping Zhong, Juan Pablo Pacheco, Franco Teixeira de Mello, Guillermo Goyenola, Juan “Checho” Clemente, Claudia Fos- alba, Soledad Garcia, Nicolás Vidal, Natalia Barberán, Malvina Masdeu, Mariana Vianna, Alejandra Kroger, Iván Gonzalez-Bergonzoni, Alejandro D’Anatro, Santiago Barberán, and Daniella Agratti. I would also like to thank landowners in both Uruguay and Denmark for al- lowing me access to the lakes. Thanks also to Unciep-Facultad de Ciencias for the offi ce space and use of labs that they provided during my work in Uruguay. I acknowledge the fi nancial support of the Ministry of Science, Technol- ogy and Innovation of Denmark. The National Research Agency (SNI and PDT) and the Scientifi c Research Commission of Uruguay (CSIC-Udelar) have also supported part of this project. Finally, I seize the opportunity to express my deep gratitude to Erik Jeppesen for his continuous support to me and my family, which made our stay in Denmark an unforgettable experience. As Meryem Beklioglu uses to say: he is “the saint of limnology”, and the medal he was recently awarded by SIL is justly deserved. 5 List of included papers Iglesias, C. , Mazzeo, N. , Meerhoff, M., Lacerot, G. , Clemente, J. , Scasso, F., Kruk, C., Goyenola, G., García, J., Amsinck S.L., Paggi, J.C., José de Paggi, S. & E. Jeppesen. High predation is the key factor for dominance of small-bodied zooplankton in warm lakes - evidence from lakes, fi sh exclosures and surface sediment. Submitted. Iglesias, C., Mazzeo, N., Teixeira de Mello, F., Goyenola, G., Fosalba C., García. S. & E. Jeppesen. 2008 Field and experimental evidence of the effect of Jenynsia multidentata Jenyns (Cyprinodontiformes, Anablepi- dae) on the size distribution of zooplankton in subtropical lakes. Fresh- water Biology. 53:1797-1807. Iglesias, C., Meerhoff, M., Vianna, M., Mazzeo, N., Pacheco, J.P., Teixeira de Mello, F., Landkildehus, F., Fosalba, C., Goyenola, G., Brix H. & Jeppesen, E. Cascading effects promoted by fi sh and macroinvertebrates on food webs of shallow lakes in different climate zones – a mesocosm experi- ment. Manuscript. Mazzeo, N., Iglesias, C., Teixeira de Mello, F., Borthagaray, A.,