Retrospective optimisation of multifunctionality on coastal urban infrastructure

A combination of reduced complexity and spatial scale underpins biodiversity and ecosystem multifunctionality deficits on artificial compared to natural habitats1. At fine-grain (mm-cm) scales, low physical complexity can inhibit the settlement/recruitment of larvae by environmentally filtering out mal-adapted organisms2. Physically simple environments can select for an over-abundance of mesopredators (e.g. limpets), whose non-selective grazing behaviour can biotically filter2 weaker species, leading to grazer dominance and "limpet barrens"3, akin to urchin barrens in subtidal systems. Here, the goal is to upscale GGI solutions to stimulate a 'multifunctional cascade' using appropriately complex surfaces to provide recruitment-phase refugia from grazing for habitat-forming species (e.g. fucoids, mussels) that, in turn, support greater biodiversity and ecosystem multifunctionality through facilitation cascades4. At medium- (e.g. cm-m) and large-grains (e.g. >10m), reduced physical complexity homogenises environmental conditions that effectively reduces niche availability, the number of species both within (a-diversity) and between patches (B-diversity)5, and site-scale (g) diversity and multi-functionality. At larger scales, regions characterised by discontinuous shorelines with mosaics of habitats (e.g. seawalls interspersed with natural reef) could support higher B-diversity compared to regions characterised by continuous homogenous vertical seawalls. This studentship will evaluate relationships between complexity, biodiversity, and ecosystem multifunctionality, and then apply this new empirical understanding to inform upscaling GGI solutions at larger scales. We propose a three-pronged state-of-art approach:
(1) Field surveys and mesocosm studies to quantify naturally-occurring relationships between physical complexity, biodiversity, and multifunctionality at multiple scales (photogrammetry/biodiversity surveys) in Plymouth Sound, Southampton Water and Milford Haven (selected due to differences in levels of urbanisation). Ecosystem multifunctionality will be estimated using functional traits databases and validated using field mesocosms. [Firth, Griffin, Foggo]
(2) Two manipulative field experiments using biomimetic tiles will determine (1) whether structural features deter/encourage key taxa and disentangle the roles of propagule pressure from physical complexity (abiotic filtering) and post-settlement biotic interactions (biotic filtering) on assemblage development; and (2) how area (scale) and spatial heterogeneity (arrangement) influence biodiversity and multifunctionality outcomes at larger spatial scales. Experiments will be deployed in Brixham (permission already granted)[Firth, Hanley, Knights]
(3) Modelling will test how the surface type, density and spatial heterogeneity of GGI patches affect accessibility and spatial use by key grazers (e.g. limpets)(see Fig 1 in OneDrive). Methods will involve in-situ surveys (photographs/time-lapse) and modelling (e.g. correlated walk models). [Firth, Knights]
The project allows the student to develop highly sought-after technical and academic skills in applied and theoretical ecological modelling, and general research skills. The supervisory team's track-record of high-quality PhD training and mentoring, evidenced by and student-led high-quality research outputs ensures an excellent student experience, including integration into a vibrant community of staff and students at UoP and abroad. UoP and ARIES training courses for continuing professional development will be encouraged, alongside presentation at international conferences (e.g. International Temperate Reefs Symposium) to develop their network and science communication skills.