University of Cincinnati

UNIVERSITY OF CINCINNATI Date:___________________ I, _________________________________________________________, hereby submit this work as part of the requirements for the degree of: in: It is entitled: This work and its defense approved by: Chair: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ Assessing the effects of predation and habitat complexity on the recovery of the long-spined sea urchin, Diadema antillarum, in Curaçao A dissertation submitted to the Division of Research and Advanced Studies of the University of Cincinnati in partial fulfillment of the requirements for the degree of DOCTORATE OF PHILOSOPHY (Ph.D.) in the Department of Geology of the College of Arts & Sciences 2008 by Elizabeth A. Dame B.S., University of South Carolina, 2002 M.S., University of Cincinnati, 2004 Committee Chair: David L. Meyer ABSTRACT Over the past several decades, decreased herbivory due to the mass mortality of a keystone grazer, the long-spined sea urchin, Diadema antillarum, has contributed significantly to the proliferation of noncoralline macroalgae on western Atlantic coral reefs, including Curaçao in the Netherlands Antilles. Nearly 25 years after the dieoff, densities of D. antillarum remain below pre-mortality levels. The recovery of D. antillarum may be slowed due to the decreasing structural complexity of reefs, as these urchins need adequate shelter to avoid predators. I tested the hypothesis that added artificial structure reduces predation and thereby increases the persistence of translocated urchins. Translocated urchins exhibited greater persistence in plots with artificial structure. The hypothesis that translocated D. antillarum exhibit differential persistence with regard to distinctive structures was also tested. Individuals exhibited greater persistence in structures that were more enclosed and better mimicked natural reef crevices. Considering that D. antillarum densities are presently higher closer to shore than on the reefs of Curaçao, I tested the hypothesis that predation pressure on D. antillarum is greater on the deeper forereef than on the shallow reef crest by surveying the densities and biomasses of predators, and the densities of D. antillarum on six reefs. Additionally, video observations on caged urchins were used to assess relative predation pressure between the two depths. Data from surveys and video experiments indicate densities of predators are not greater on the forereef when compared to the reef crest. There was no significant correlation between D. antillarum densities and predator densities, or between D. antillarum densities and predator biomass on the reef crest or the forereef. I also surveyed these six reefs to examine the relationship between D. antillarum densities, topographic complexity, and reef condition. Diadema antillarum densities were not iii linked with topographic complexity on the reef crest; however, a positive correlation existed between urchin densities and habitat complexity on the forereef. Habitat complexity is likely limiting recovery of this urchin in greater depths. This study demonstrates the importance of conducting restoration studies that integrate an experimental and ecological approach to gain a better understanding of factors limiting recovery of D. antillarum. iv ACKNOWLEDGEMENTS I would like to thank my advisor, David Meyer, for his guidance, support, and knowledge of Caribbean coral reefs. I greatly appreciate the suggestions and expertise of my committee members, Eric Maurer, Arnie Miller, Ken Petren, and George Uetz. I offer many thanks to my field assistants, Tom Dame, Cory Christopher, Lauren Dame, Justin Wise, Ashley Allemang, and David Meyer. I would also like to thank Anne-Marie Vermeer of Easy Divers at Habitat Curaçao for her cooperation. Financial support for this research was provided by the K.E. Caster Fund of the Department of Geology and the Office of Research at the University of Cincinnati, and by a Grant-In-Aid of Research from Sigma Xi, The Scientific Research Society. I am exceedingly grateful for the George and Frances Rawlinson Fellowship and Cook Scholarship provided by the Department of Geology, during my final academic year. I am indebted to my parents and family for their enduring encouragement and their multiple trips to Curaçao to assist me. Last, but never least, I would like to thank my husband for providing invaluable insight as a fellow scientist and for keeping me sane. vi TABLE OF CONTENTS List of Tables……………………………………………………………………………………..ix List of Figures……………………………………………………………………………………..x Introduction Chapter…...…………...……………………………………………………………..1 References…………………………………………………………………………………..5 Chapter 1: Assessing the status of coral reefs in Curaçao and the effect of habitat complexity on the recovery of Diadema antillarum, the long-spined sea urchin Abstract……………………………………………………………………………………..8 Introduction…………………………………………………………………………………8 Methods……………………………………………………………………………………13 Results……………………………………………………………………………………..17 Discussion………………………………………………………………………………….22 Acknowledgements………………………………………………………………………..27 References…………………………………………………………………………………28 Appendix 1………………………………………………………………………………...47 Appendix 2………………………………………………………………………………...57 Appendix 3………………………………………………………………………………...60 Chapter 2: Assessing the effect of predation on the distribution and abundance of Diadema antillarum in Curaçao, Netherlands Antilles Abstract…………………………………………………………………………………….66 Introduction………………………………………………………………………………..67 Methods……………………………………………………………………………………70 vii Results……………………………………………………………………………………..74 Discussion………………………………………………………………………………….77 Acknowledgements………………………………………………………………………..81 References…………………………………………………………………………………81 Chapter 3: Assessing the effect of artificial habitat structure on translocation of the long-spined sea urchin, Diadema antillarum, in Curaçao (Netherlands Antilles) Abstract…………………………………………………………………………………….96 Introduction………………………………………………………………………………..97 Methods…………………………………………………………………………………..100 Results………………………………………………………………………………...….103 Discussion……………………………………………………………………………...…104 Acknowledgements……………………………………………………………………....107 References…………………………………………………………………………..……107 Conclusions Chapter……………………………………………………………………………115 References………………………………………………………………………………..117 viii LIST OF TABLES Chapter 2 Table 1. Surveyed biomass of known fish predators by depth interval and their percentage of total predator biomass by depth interval……………………………………………….86 Table 2. Known predatory reef fish of D. antillarum and their occurrences (no. of frames) in the shallow reef crest and deeper forereef sites of the video experiments……………..87 ix LIST OF FIGURES Chapter 1 Figure 1. Location of survey sites along the leeward coast of Curaçao: 1= Rif St. Marie; 2= Playa Porto Marie; 3= Daaibooi; 4= Slangenbaai; 5= Jan Thiel; 6= Playa Lagun……..33 Figure 2. Species composition and relative abundance of all stony coral and Millepora species for colonies ≥ 10 cm in length on the a) seaward reef crest, and b) forereef…...…35 Figure 3. Percent cover of coral and macroalgae for the a) reef crest, and b) forereef……37 Figure 4. Maximum relief (mean ± S.E.) above substratum on the reef crest (1-5 m depth) and forereef (8-15 m depth) for all sites…………………………………………………...39 Figure 5. Diadema antillarum densities (No./100m2) versus maximum reef relief (cm) across all sites on a) the reef crest (1-5 m depth), and b) the forereef (8-15 m depth)…….41 Figure 6. Mean density (number of individuals per 100 m2 ± SD) of AGRRA reef fish families surveyed on the seaward reef crest (1-5 m depth) and shallow forereef (8-15 m depth)………………………………………………………………………………………43 x Figure 7. Partial percent mortality (recent, old, and total) of all coral colonies on the a) reef crest, and b) forereef…………………………………………………………………..45 Chapter 2 Figure 1. Location of survey sites along the leeward coast of Curaçao: 1= Rif St. Marie; 2= Playa Porto Marie; 3= Daaibooi; 4= Slangenbaai; 5= Jan Thiel; 6= Playa Lagun…….88 Figure 2. Cage for monitoring tranlocated urchins in video experiments………………...90 Figure 3. a) Diadema antillarum and predator densities on the reef crest. b) Diadema antillarum and predator densities on the forereef………………………………………….92 Figure 4. a) Predator biomass on the reef crest and forereef. b) Diadema antillarum densities on the reef crest and forereef…………………………………………………….94 Chapter 3 Figure 1. Artificial structures added to experimental translocation plots to serve as shelter from predation: a) brick and tile “hut” shelter and b) roof tile “tunnel” shelters………...111 Figure 2. Mean number of translocated Diadema antillarum remaining (± SE) over time in the huts, tunnels, and outside of the shelters in the experimental plots…………….…….113 xi INTRODUCTION CHAPTER Determining changes in community structure is a major objective of ecology (Hughes 1996). However, it is becoming increasingly more difficult to establish community composition for a “pristine” environment as communities are ever more affected by anthropogenic influences. Moreover, climatic changes make forecasting the composition of future communities complicated (Williams and Jackson 2007). Consequently, maintaining the resilience of ecosystems should be a fundamental constituent of conservation strategies (Knowlton 2004). Western Atlantic coral reef ecosystems are an epicenter for biodiversity and therefore of global importance in the field of conservation biology.

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