The ecology of marine tidal race environments and the impact of tidal energy development Melanie Broadhurst A thesis submitted for the degree of Doctor of Philosophy from the Division of Biology, Department of Life Sciences, Imperial College London 2 Abstract Marine tidal race environments undergo extreme hydrodynamic regimes and are favoured locations for offshore marine renewable tidal energy developments. Few ecological studies have been conducted within these complex environments, and therefore, ecological impacts from tidal energy developments remain unknown. This thesis aimed to investigate the ecological aspects of marine tidal race environments in two themes, using a combination of field-based sampling techniques. I first examined the natural ecological variation of a marine tidal race environment at the spatial and temporal scale. These studies were based on the benthic and intertidal communities within the Alderney Race tidal environment, Alderney. My results suggest that both communities vary in species diversity and composition, at different spatial gradients and timescales. Species showed opportunistic or resilient life history characteristics, highlighting the overall influence of the strong hydrodynamic conditions present. I then explored the ecology of a marine tidal race environment within a renewable tidal energy development site. These studies were based within the European Marine Energy Centre’s tidal energy development site, Orkney. Here, I investigated ecological variation in terms of fish interaction and benthic assemblage structure with a deployed tidal energy device, and, the structure of intertidal communities within the overall development site. Interestingly, my results indicated species-specific interactions with the deployed tidal energy device, which was related to species’ refuge or feeding behaviour. These results also imply that different communities show varied spatial and temporal heterogeneity within a development site, associated with the complex interplay of abiotic and biotic processes. This work begins to reveal the ecological consequences of tidal energy development, with single devices acting as potential short-term artificial reef structures. Further research is recommended within these environments, with reference to how the hydrodynamic regimes directly influence these communities, and, the overall ecological consequences of future large-scale tidal energy development scenarios. 3 Declaration All work presented in this thesis is my own, with the following acknowledgements: Most of the data have been collected by me, where collected with others, or datasets compiled by others, I cite appropriately throughout. This includes all reference published software and programming code. All chapters have received editorial advice and comment from my thesis supervisors David Orme (Imperial College London) and Mike Eggleton (ARE Ltd). Chapter 4 is co-authored with the operations manager of OpenHydro Ltd, Sue Barr and David Orme. This work was a collaborative project with OpenHydro Ltd, which included the development of the sampling method and data collection. Acknowledgements from the chapters: Chapter 2. I am grateful to ARE Ltd for their help in selecting the survey locations and access to bathymetry information. The assistance of the crew of Dizzy and other vessels during the data collection. Chris Wood and Richard Lord for species identification help. Chapter 3. I am grateful to ARE Ltd for their help selecting survey locations. The assistance of the Alderney Wildlife Trust during the data collection. Richard Lord for species identification help. Sarah Edwards for her comments on the draft manuscript. Chapter 4. I am grateful to OpenHydro Ltd colleagues for assistance in the data collection. Thanks to EMEC for access to the tidal test site and general advice. Two anonymous reviewers of the preliminary manuscript written for the EWTEC 2011 conference. Sarah Whitmee and Mike Eggleton for their comments on the final manuscript. Chapter 5. I am grateful to EMEC and OpenHydro Ltd for access to the tidal test site and test device platform. The assistance of the crew of Medina II during the data collection. Delphine Coates for her comments on the final manuscript. Chapter 6. I am grateful to EMEC for access to the tidal test site. Andrew Want and Rob Beharie for their discussions, assistance with data collection, species identification and comments on the draft manuscript. 4 Copyright declaration ‘The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work’. 5 Acknowledgements I would first like to thank the BBSRC and ARE Ltd in collaboration with Imperial College London for giving me the opportunity for this PhD Case studentship. I would also like to extend these thanks to the Channel Islands Co-operative, Cheape Charitable Trust and Lloyds TSB Offshore Trust Company Ltd for providing funds towards the sampling equipment and surveying costs. I would like to thank my supervisors David Agnew and Sally Powers for the ideas and discussions that inspired me from the very beginning. I am truly indebted to my supervisor David Orme, thank you for giving me the scope to undertake this research, to constantly make me think big (both in space and time) and to keep calm, throughout this study. I am extremely grateful to my ARE Ltd Case supervisor, Mike Eggleton. Thank you for the enlightening help on all energy matters, the laughter, and the hospitality both you and Sheila have given me over the years. Many thanks go to my PRP’s, Rob Ewers and Blake Suttle. Thank you both for reminding me to look back theoretically and to keep up the replication effort. To ARE Ltd, EMEC, and OpenHydro Ltd, thank you all for giving me the means, motive, advice and access whilst answering all my never-ending questions. I would particularly like to thank Sue Barr from OpenHydro Ltd. Part of this research was inspired from our meetings, including giving me the courage to devise the project in the first place, for which I am eternally grateful. My biggest thanks go to all the individuals that have helped me during my data collection on both sides of the British Isles. This includes the offshore crews (and families) of Dizzy, Medina II, Nomad, Obelix, Rib Eye and Voyager. Above all, to Mel Roots and Martin Smith, for your willingness to help build ‘Stingray’ and perseverance of my incessant cooing’s over Porifera whilst at sea. To Stevie, thank you for getting me through my first unexpected, yet amazing force 10 storm and the laughter that ensued. I would also like to thank Rob Beharie, Richard Lord, Andrew Want, Chris Wood, the Alderney Society and the Alderney Wildlife Trust for all your assistance during the intertidal data collection, species identification debates and debacles. It was a real pleasure and an unforgettable experience. In addition, many thanks to Sarah Edwards and Delphine Coates for the editorial help and Lisa Saunders for the image help, for which I am very, very grateful. 6 A plethora of thanks go to the Silwood terrestrial lot, especially Lynsey McInnes, Hannah Peck, Alex Pigot and Sarah Whitmee (and Whitmee family). Thank you for putting up with my nomadic tendencies (both physically and mentally), your wise-owl-words and lovely tea- cake-pancake breaks. I could not think of a more helpful, constructive or enjoyable time on land, particularly towards the end. To my family and friends, I cannot put into words what it has meant to have had your support over the last few years. Mum, dad and Keith, thank you for putting up with my sampling highs, my travelling woes and writing up panics. It has been (and still is) a fantastic journey, for which I could not have done without you. Thank you from the bottom of my sand filled pockets. “The sea, once it casts its spell, holds one in its net of wonder forever.” Jacques Yves Cousteau 7 Table of contents Abstract ................................................................................................................................................... 2 Declaration .............................................................................................................................................. 3 Copyright declaration .............................................................................................................................. 4 Acknowledgements ................................................................................................................................. 5 Table of contents ..................................................................................................................................... 7 Chapter 1. Introduction ........................................................................................................................... 9 1.1. The marine tidal race environment ......................................................................................... 9 1.2. The ecology within marine tidal race environments ............................................................. 12 1.3. Marine renewable energy development ...............................................................................