University of Wollongong Research Online University of Wollongong Thesis Collection 2017+ University of Wollongong Thesis Collections 2017 Cut adrift: the distribution and abundance of rafting algae and its associated fauna now and in a future ocean Lauren Jean Cole University of Wollongong Follow this and additional works at: https://ro.uow.edu.au/theses1 University of Wollongong Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part of this work may be reproduced by any process, nor may any other exclusive right be exercised, without the permission of the author. 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Recommended Citation Cole, Lauren Jean, Cut adrift: the distribution and abundance of rafting algae and its associated fauna now and in a future ocean, Doctor of Philosophy thesis, School of Biological Sciences, University of Wollongong, 2017. https://ro.uow.edu.au/theses1/121 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] Cut adrift: the distribution and abundance of rafting algae and its associated fauna now and in a future ocean A thesis submitted in fulfilment of the requirements for the award of the degree DOCTOR OF PHILOSOPHY From UNIVERSITY OF WOLLONGONG By Lauren Jean Cole, Bachelor of Science CENTRE FOR SUSTAINABLE ECOSYSTEM SOLUTIONS SCHOOL OF BIOLOGICAL SCIENCES 2017 II CERTIFICATION I, Lauren Jean Cole, declare that this thesis, submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy, in the Centre for Sustainable Ecosystem Solutions, School of Biological Sciences, University of Wollongong, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualifications at any other academic institution. All work conducted for this dissertation was conducted under the NSW DPI Research Permit F95/269-8.0. Lauren Cole 6th July 2017. III IV TABLE OF CONTENTS TABLE OF CONTENTS……………………………………………………………………V LIST OF FIGURES……………………………………………………………………………………………...… IX LIST OF TABLES……………………………………………………………………………………...……....... XIII ABSTRACT………………………………………………………………………………………………………….... XV ACKNOWLEDGEMENTS………………………………………………………………………...………… XVII CHAPTER 1 – GENERAL INTRODUCTION………………………………………………….……….. 1 1.1. IMPORTANCE OF DISPERSAL IN MARINE ENVIRONMENTS………………………………………. 2 1.1.1. Rafting as a Mode of Dispersal……………...…………………………………...………………. 2 1.1.2. The Dispersal Capability of Rafts…………………………………………..……………………. 4 1.2. RAFTS AND RAFTERS……………………………………………………………………………………. 5 1.2.1. The Origin of Rafts………………………………………………………………………………. 5 1.2.2. The Life of a Rafter………………………………………………………………………………. 7 1.3. KEY THEMES OF RESEARCH ON ALGAL RAFTING COMMUNITIES…………………….…..……. 9 1.4. RAFTING IN A FUTURE OCEAN…………………………………………..…………………………… 12 1.5. AIMS OF THE STUDY ...………………………………………..………………………………………... 13 CHAPTER 2- TRENDS IN RAFT ABUNDANCE, BIOMASS AND DISTRIBUTION ALONG THE SOUTHERN NEW SOUTH WALES COASTLINE………………….... 16 2.1. INTRODUCTION………………………………………………………………………………………….. 17 2.2. METHODS…………………………………………………………………………………………………. 20 2.2.1. Study Locations…………………………………………………………...…………………….. 20 2.2.2. Sampling Design…………………………………………………………...………………….... 22 2.2.3. Analysis of data…………………………………………………………...…………………….. 24 2.3. RESULTS…………………………………………………………...…………………………………….... 25 2.3.1. Spatial and Temporal Trends in Raft Abundance and Biomass………………………………... 25 2.3.2. Comparing Invertebrate Communities………………………………………………………….. 28 2.4. DISCUSSION…………………………………………………………...…………………………………. 31 V 2.4.1. Spatial and Temporal Trends in Raft Abundance and Biomass ……………………………….. 32 2.4.2. Comparing Invertebrate Communities………………………………………………………….. 35 2.4.3. Implications and outlook………………………………………………………………….…….. 37 CHAPTER 3- THE DISTRIBUTION OF FLOATING AND BEACH-CAST ALGAL RAFTS ALONG THE NSW COASTLINE …………...……………………………….... 38 3.1. INTRODUCTION………………………………………………………………….………………………. 39 3.2. METHODS………………………………………………………………….…………………………….... 42 3.2.1. Beach and Aerial Surveys………………………………………………………………………. 42 3.2.2. Survey design………………………………………………………………….………………... 44 3.2.3. Analysis of data………………………………………………………………….…………….... 45 3.3. RESULTS………………………………………………………………….……………………………….. 46 3.3.1. Beach Surveys………………………………………………………………….……………….. 46 3.3.2. Aerial Surveys………………………………………………………………….……………….. 47 3.3.3. The relationship between rafts and Phyllospora reefs………………………………………….. 48 3.4. DISCUSSION………………………………………………………………….…………………………... 50 CHAPTER 4 –TRENDS IN ABUNDANCE AND DIVERSITY OF RAFT- ASSOCIATED INVERTEBRATES……………………………………………………… 54 4.1. INTRODUCTION ………………………………………………………………….…………………….... 55 4.2. METHODS………………………………………………………………….……………………………… 58 4.2.1. Laboratory methods……………………………………...……………………….…………….. 58 4.2.2. Analysis of data………………………………………………………………….…………….... 59 4.3. RESULTS………………………………………………………………….……………………………….. 60 4.3.1. The rafting community: Spatial and Temporal Trends…………………………………………. 60 4.3.2. The growth and development of Portunus spp. on rafts………………………………………... 65 4.4. DISCUSSION………………………………………………………………….…………………………... 66 4.4.1. The rafting community: Spatial and Temporal Trends………………………..………….…….. 66 4.4.2. The growth and development of Portunus spp. on rafts………………………………………... 69 4.4.3. Conclusions……………………………………………………………………………….…….. 71 VI CHAPTER 5 – FLOATING RAFTS: ISOLATED ISLANDS OR ACTIVE ARCHIPELAGO?................................................................................................................. 72 5.1. INTRODUCTION………………………………………………………………….………………………. 73 5.2. METHODS………………………………………………………………….……………………………… 76 5.2.1. Sampling Design………………………………………………………………….…………...... 76 5.2.2. Analysis of data………………………………………………………………….…………….... 77 5.3. RESULTS ………………………………………………………………….………………………………. 78 5.4. DISCUSSION………………………………………………………………….…………………………... 81 CHAPTER 6 – RAFTS IN A FUTURE OCEAN………………………………………... 86 6.1. INTRODUCTION…………………………………………………………...……………………….…….. 87 6.2. METHODS………………………………………………………………….…………………………….... 90 6.2.1. Study location and design………………………………………………………………….….... 90 6.2.2. Measures of rafts fitness………………………………………………………………….…….. 92 6.2.3. Analysis of Data………………………………………………………………….……………... 93 6.3. RESULTS………………………………………………………………….……………………………….. 93 6.4. DISCUSSION………………………………………………………………….…………………………... 98 6.4.1. Conclusions…………………………………………………………………...…...…………... 101 CHAPTER 7- MODELLING THE IMPACTS OF A FUTURE OCEAN ON A KEY HABITAT-FORMING MACROALGA: A BAYESIAN NETWORK APPROACH.. 103 7.1. INTRODUCTION………………………………………………………………….……..………………. 104 7.2. METHODS………………………………………………………………….…………………...………....107 7.2.1. Description of the model………………………………………………………………….….... 107 7.2.2. Description and parameterisation of the variables ……………………...…………….………. 108 7.2.2.1. Decision Nodes…………………………………………...………………….…….. 108 7.2.2.2 Intermediate Nodes………………………………………………………………..... 110 7.2.2.3. Output Nodes………………………………………………………………….….... 114 7.2.3. Sensitivity analysis………………………………………………………………….…………. 116 7.3. RESULTS………………………………………………………………….…………………………….... 116 VII 7.3.1. Model outcomes and predictions…………………………………………………………….... 116 7.3.2. Sensitivity analysis………………………………………………………………….…………. 118 7.4. DISCUSSION………………………………………………………………….……………………...….. 120 5.4.1. Sensitivity analysis………………………………………………………………….…………. 122 7.4.2. Conclusion ……………………..……………………………………………………….…….. 122 CHAPTER 8 – GENERAL DISCUSSION…………………………..…………………. 125 8.1. GENERAL FINDINGS AND CONSISTENCY WITH PREVIOUS RESEARCH………………..…….. 126 8.2 FUTURE DIRECTIONS………………………………………………………………….……………….. 128 8.3. POTENTIAL IMPLICATIONS OF FINDINGS…………………………………………………………. 130 REFERENCES………………………………………………………………………….... 132 VIII LIST OF FIGURES Figure 1.1. Relative proportion of taxa reported or inferred as utilizing floating rafts during previous surveys. Data from Thiel & Gutow (2005b) ………...…………………………. 8 Figure 1.2. Relative abundance of regions where previous research has been conducted on the use of rafts by epifauna. Data from by Thiel et al. (2005b) ………...………………. 10 Figure 2.1. New South Wales, Australia, with inset of study sites Port Kembla and Jervis Bay along the coastline south of Sydney. The locations of rocky reefs indicated along shorelines in grey. Scales for each location identified in bottom right corner. …………. 22 Figure 2.2. Path of Port Kembla survey on April 28, 2013. Example of the path taken during a Port Kembla survey. ………...………………………….………...……………...……. 23 Figure 2.3. Concentration and composition of rafts floating throughout Jervis Bay (A) and Port