Bangor University DOCTOR OF PHILOSOPHY Stability and variability of the ecosystem engineer Sabellaria alveolata on differing temporal and spatial scales Bush, Laura Award date: 2016 Awarding institution: Bangor University Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 10. Oct. 2021 Stability and variability of the ecosystem engineer Sabellaria alveolata on differing temporal and spatial scales. A thesis presented by Laura Elizabeth Bush B.Sc. M.Sc. to the School of Ocean Sciences, Bangor University in partial fulfilment of the requirements for the award of Doctor of Philosophy Date: 31/12/2015 i II. Acknowledgements I am pleased to acknowledge the support of the Cemlyn Jones Trust through provision of the Cemlyn Jones Studentship. Additional funding was provided by the Dennis Crisp Fund, the Porcupine Marine Natural History Society, Natural Resources Wales (formerly Countryside Council of Wales) and the Natural History Museum, London. Being a typical PhD student I didn’t just utilise all available pots of money, I also dipped all available wells of knowledge, and mined both friends and acquaintances for their expertise at every turn: Dr Andrew Davies and Professor Steve Hawkins, I couldn’t have done it without you; Dr Gay Mitchelson-Jacob, many thanks for being my supervisor; Stephen Balestrini, Elisha Slater, Farng Kringpaka, and Abby Gilson, your enthusiasm got me through some dark and muddy times; Dr Louise Firth, I will forever associate ‘broad-scale, long-term’ with you; and my family and friends, those who are still with me and those who aren’t, to all of you, there may have been points when I took you thoughtlessly for granted but believe me when I say your endless patience has been appreciated every long step of the way. ii III. Abstract Climate change is directly and indirectly impacting biota, A common prediction is that biogeographic ranges will extend poleward, with increases in abundance near the leading edge. Understanding how marine species will respond is hindered by a scarcity of long-term datasets. However, within the British Isles there is a long history of well-documented intertidal research. Historical data are stored in a variety of forms from grey-literature and national databases to published journals. Sabellaria alveolata is a conservationally important biogenic reef-forming species that reaches its northern range limit within the British Isles. The aim of this thesis was to establish if S. alveolata has responded predictably to climate change, and to investigate abiotic and biotic drivers of observed change. Through comparisons with historical and contemporary collated and collected data on different spatial scales, it was clear that S. alveolata has exhibited persistence in distribution, and stability in abundance and morphology on a long term, broad spatial scale with no significant difference in distribution, abundance or reef-forming morphology exhibited from the 1980s to the 2010s (>50 % stability in all paired data; Bush et al., Chapter 2). Within this, S. alveolata populations have demonstrated change on reduced spatial scales, increasing in response to increased temperature near the northern range edge, with some decreases in response to increased wave exposure well within the range (explaining ~ 50 % of the variance in both instances; Bush et al., Chapter 3). Through long-term monitoring studies, this study demonstrated high within-site variability. Additionally evidence was provided that, within Britain, the intertidal ecosystem engineers S. alveolata and Mytilus edulis are alternative stable state communities on pebble shores, with complete change of state from S. alveolata dominated to M. edulis dominated reef in 1 year (Bush & Davies, Chapter 4). State is partially maintained by settlement success in both instances (R2 ≥ 0.55). Finally, through a combination of traditional monitoring and laboratory techniques with state of the art modelling approaches, this study provided insights into reproductive strategy, larval dispersal and population connectivity patterns of S. alveolata and provided evidence of subpopulations of reef-forming species on British coastlines (e.g. Scotland to North Wales, Mid Wales, and South Wales to Southwest England; Bush et al., Chapter 5). iii Index Page I. Declarations I Declaration of authorship I Statement of originality I Statement regarding availability I II. Acknowledgements II III. Abstract III 1. Introduction 1 1.1. Importance of long-term datasets 1 1.2. Stability and variability of coastal marine habitats 2 1.3. Ecosystem Engineers 5 1.4. Sabellaria alveolata 5 1.4.1. Importance of habitat 5 1.4.2. Biology 9 1.4.3. Potential for changes to biogeography 13 1.5. The Sabellaria alveolata community as an alternative stable state 14 1.6. Outline of thesis 18 1.7. References 21 2. Persistence and stability of the biogenic reef-forming polychaete, Sabellaria alveolata (L.) in the British Isles 33 Declaration 33 2.1. Abstract 34 2.2. Introduction 35 iv 2.3. Methodology 39 2.3.1. Historical Sabellaria alveolata data 39 2.3.2. Sabellaria alveolata data collection 43 2.3.3. Defining “reefs” within qualitative observations 43 2.3.4. Assessing change in distribution and abundance 44 2.4. Results 47 2.4.1. Change in distribution 47 2.4.2. Change in SACFOR abundance and morphology 52 2.5. Discussion 56 2.5.1. Persistence and stability 56 2.5.2. Change in distribution 58 2.5.3. Change in abundance 60 2.6. Conclusions 62 2.7. Acknowledgements 62 2.8. Appendices 63 2.9. References 135 3. Regional-scale dynamics of Sabellaria alveolata abundance and distribution over 3 decades 147 Declaration 147 3.1. Abstract 148 3.2. Introduction 149 3.3. Study Area and Methods 154 3.3.1. Study area 154 3.3.2. Historical Sabellaria alveolata abundance data within Britain 154 v 3.3.3. Assessing regional change in distribution, abundance and morphology 156 3.3.4. Assessing regional change in environmental parameters 157 3.3.5. Changes in Sabellaria alveolata distribution, abundance and morphology related to environmental parameters 159 3.4. Results 160 3.4.1. Regional change in distribution 160 3.4.2. Regional change in SACFOR abundance and morphology 163 3.4.3. Regional changes in environmental parameters 168 3.4.4. Impact of environmental parameters on Sabellaria alveolata distribution 170 3.4.5. Impact of environmental parameters on Sabellaria alveolata abundance and morphology 171 3.5. Discussion 173 3.5.1. Environmental drivers of change 173 3.5.2. Natural resilience of Sabellaria alveolata 176 3.5.3. Knowledge gaps and opportunities 177 3.6. Conclusions 180 3.7. Acknowledgements 181 3.8. Appendices 182 3.9. References 188 4. Site-specific conditions trigger switch between alternative states in temperate intertidal reefs 201 Declaration 201 4.1. Abstract 202 4.2. Introduction 203 vi 4.3. Study Area and Methods 208 4.3.1. Study area 208 4.3.2. Sampling methodology 208 4.3.3. Data analysis 211 4.4. Results 212 4.4.1. Overall site classification using SACFOR 212 4.4.2. Percentage cover of Sabellaria alveolata 212 4.4.3. Reef Height 213 4.4.4. Sabellaria alveolata condition 216 4.4.5. Percentage cover of Mytilus edulis 218 4.4.6. Sabellaria alveolata: Mytilus edulis dynamic 218 4.4.7. Mytilus edulis cover: settlement success 220 4.4.8. Sabellaria alveolata cover: settlement success 220 4.5. Discussion 223 4.5.1. Stability and variability in Sabellaria alveolata reef 223 4.5.2. Sabellaria alveolata: Mytilus edulis dynamic 225 4.5.3. Future Considerations 229 4.6. Conclusions 230 4.7. Acknowledgements 231 4.8. Appendices 232 4.9. References 233 5. Linking larval dispersal to adult persistence in the ecosystem engineer Sabellaria alveolata 241 Declaration 241 5.1. Abstract 242 vii 5.2. Introduction 243 5.21. Study species life cycle 246 5.5. Study Area and Methods 249 5.3.1. Study area 249 5.3.2. Fecundity of Sabellaria alveolata adults 249 5.3.3. Spawning and rearing Sabellaria alveolata larvae 251 5.3.4. Sabellaria alveolata larval behaviour in vivo 252 5.3.5. Temporal and spatial variability in in concentration of Sabellaria alveolata larvae 253 5.3.6. Biophysical modelling of Sabellaria alveolata larvae 254 5.3.7. Validation of vertical Sabellaria alveolata larval migration with in situ observations 256 5.3.8. Validation of horizontal Sabellaria alveolata larval dispersal with in situ observations 258 5.4. Results 259 5.4.1. Fecundity of Sabellaria alveolata adults 259 5.4.2. Sabellaria alveolata larval behaviour in vivo 261 5.4.3. Temporal and spatial variability in concentration of Sabellaria alveolata larvae 262 5.4.4. Biophysical modelling of Sabellaria alveolata larvae – Passive particles 265 5.4.5. Biophysical modelling of Sabellaria alveolata larvae – Diel vertical migration 270 5.4.6. Validation of vertical Sabellaria alveolata larval migration with in situ observations 271 5.4.7. Validation of horizontal Sabellaria alveolata larval dispersal with in situ observations 271 viii 5.5. Discussion 273 5.5.1. Spawning strategy in Sabellaria alveolata 273 5.5.2.