THE IMPACT OF MULTIPLE STRESSORS ON COASTAL BIODIVERSITY AND ASSOCIATED ECOSYSTEM SERVICES Stephen Christopher Lewis Watson A Thesis Submitted for the Degree of PhD at the University of St Andrews 2017 Full metadata for this thesis is available in St Andrews Research Repository at: http://research-repository.st-andrews.ac.uk/ Please use this identifier to cite or link to this thesis: http://hdl.handle.net/10023/16817 This item is protected by original copyright This item is licensed under a Creative Commons Licence https://creativecommons.org/licenses/by-nc-nd/4.0/ The Impact of Multiple Stressors on Coastal Biodiversity and Associated Ecosystem Services. Stephen Christopher Lewis Watson This thesis is submitted in partial fulfilment for the degree of PhD at the University of St. Andrews April 2017 1 1. Candidate’s declarations: I, Stephen Watson hereby certify that this thesis, which is approximately 72, 120 words in length, has been written by me, and that it is the record of work carried out by me, or principally by myself in collaboration with others as acknowledged, and that it has not been submitted in any previous application for a higher degree. I was admitted as a research student and as a candidate for the degree of PhD in March, 2013; the higher study for which this is a record was carried out in the University of St Andrews between 2013 and 2017. Date Signature of candidate 2. Supervisor’s declarationI hereby certify that the candidate has fulfilled the conditions of the Resolution and Regulations appropriate for the degree of PhD in the University of St Andrews and that the candidate is qualified to submit this thesis in application for that degree. Date Signature of supervisor 3. 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The following is an agreed request by candidate and supervisor regarding the publication of this thesis: Embargo on all of print and electronic copies for a period of 1 year on the following ground(s): Publication would preclude future publication Date Signature of candidate Signature of supervisor 2 Acknowledgements First and foremost I want to thank my advisor Dr Nicola Beaumont, you have been a tremendous mentor for me. All of your advice over the past four years has been priceless and I would like to thank you for encouraging my research (including my first scientific paper!) and for allowing me the independence to grow as a research scientist. Also at Plymouth Marine Lab (PML), I would like to thank all of the members of the Sea and Society and Marine Ecology and Biodiversity Research Groups for including me in group discourse and proving cake and coffee along with much needed thesis support when I had burning questions. I would also like to thank, each of the respective heads of science Professors Melanie Austen and Steve Widdicombe for sharing their impressive academic, statistical and vocational knowledge and in helping me to present my research at a number of local and international events. I also owe a big thank you to Dr Sheila Heymans (The Scottish Association for Marine Science, SAMS) and Dr Paul Somerfield (PML) for providing data for this project and Ecopath/PRIMER-e support. In St. Andrews, a huge thank you to my supervisor Professor David Paterson. Having known Dave prior to this PhD through my MRes in St. Andrews, I am eternally grateful that Dave could see potential in me for this particular project. In short, thanks Dave for the brilliant advice, discussions and hints at interpreting my results even on my often hurried visits to St. Andrews - all of your time was greatly appreciated. Additional thanks to the rest of the members of SERG for making me feel welcome and for letting me claim desk space on my occasional visits. Special thanks too Andy, Irvine, Jack and Eugenia for helping me to plan most of my Eden lab and field work and for accompanying me out on the mud. At this point I would like to thank my family. Words cannot express how grateful I am to my mother and father, for all of the sacrifices that you’ve made on my behalf. Your continuous belief that I can achieve anything is a constant source of encouragement to me and is what has sustained me thus far. Thanks for letting me stay with you on my all too infrequent visits to St. Andrews, without my “Scottish base” this project would be been inevitably more challenging and potentially unworkable. I would also like to thank my brother Callum and non-academic friends in Scotland (and soon to be best men: Andy, Chris, Dave, Martyn) who proved light relief from the writing, and incentivised me to strive towards my final deadline by booking my stag to Oktoberfest Germany a few weeks before my targeted deadline…cheers guys! At the end, I would like express appreciation for my fiancée, Ffion, who spent countless hours correcting my errant grammatical mistakes and was always my support in the moments when there was no one to answer my queries. 3 Abstract Marine and coastal ecosystems are subject to diverse and increasingly intensive anthropogenic activities, making understanding cumulative effects critically important. However, accurately accounting for the cumulative effects of human impacts can be difficult, with the possibility of multiple stressors interacting and having greater impacts than expected, compounding direct and indirect effects on individuals, populations, communities and ecosystems. Assessment of multiple stressors therefore requires extensive scientific research that directly tests how single or multiple ecological components are affected by stressors, both singly and when combined, and as a consequence, cumulative effects assessments are now increasingly included in environmental assessments. Currently, there is a need to assess these at larger spatial scales, with additional research also urgently needed on the responses of ecological components, processes and functions to single and cumulative stressors. As cumulative environmental impacts could be better addressed by regional stressor effects assessments that combine methods for predicting multiple pressures on ecosystem recovery alongside degradation, this study used several separate approaches that can be used in parallel to give support for local management measures. I tested four completely different methods – a range of multi-metric indices, a food web model (Ecopath), a predictive model (Ecosim) and a Bayesian Belief Network model. Each approach was tested and compared in two shallow water estuarine systems, in Scotland and England, initially concerning the impact of nutrient enrichment and subsequent recovery and was followed by an investigation of how the addition of multiple stressors (nutrient levels, temperature and river-flow rates) would impact the future state of each system. The response to stressors was highly context dependent, varying between and within geographic locations. Overall, each of the four different approaches complemented each other and gave strong support for the need to make big reductions in the pressures and to consider trade-offs between impacting pressures. The models and tools also indicate that in order to reach an improved overall environmental state of each ecosystem, a focus on nutrient reductions are likely to be the most effective of the controls on stressors explored and that cumulative effects of the management of nutrient inputs and increased water temperatures and river-flow are likely to exist. Keywords Climate change, marine systems, multiple stressors, biodiversity, ecosystem services, ecosystem health, resilience, nutrient stress, Ecopath, ecological indices, macro-invertebrates, demersal fish, waterbirds. 4 Table of Contents Chapter 1: General introduction ............................................................................................................ 7 Chapter Summary ............................................................................................................................... 7 1.1 The impact of multiple stressors on coastal systems ................................................................. 7 1.2 Implications of changing biodiversity on marine ecosystem functioning .................................. 9 1.3 Ecosystem services and benefits from marine systems ............................................................ 11 1.4 Concepts of ecosystem health, resilience and sustainability ................................................... 18 1.5 Developing appropriate indicators for ecosystem service assessments under changing environmental conditions. ..............................................................................................................