Biogeomorphology of Coastal Structures: Understanding interactions between hard substrata and colonising organisms as a tool for ecological enhancement

Abstract

Urbanisation is increasingly recognised as a major ecological pressure at the coast. By 2035, the Department for Environment, Food and Rural Affairs will have to spend £1 billion each year on flood defence and erosion control infrastructure if current levels of protection are to be sustained in England and Wales; this represents a substantial commitment to building new hard structures. Ecological research has shown that structures like seawalls, breakwaters, and harbour and port infrastructure are poor surrogates for undisturbed rocky shores. This, alongside substantial international policy drivers, has led to an interest in the ways in which structures might be enhanced for ecological gain. Virtually all of this research has been undertaken by ecologists, while the contribution of geomorphological understanding has not been fully recognised. This thesis presents an assessment of the two-way interactions between colonising organisms and the materials used to build hard coastal structures under a framework of biogeomorphology. The influence of material type and small-scale surface texture on early colonisation is assessed alongside detailed observations of the ways in which biota are involved in the alteration of substratum properties and behaviours through weathering and erosion in the intertidal zone. The research demonstrates that biotic (organisms) and abiotic (material substrata) components of coastal structures are inherently linked at various spatial and temporal scales through complex biogeomorphic interactions and feedbacks. Importantly, these interactions have consequences for the subsequent operation of ecological and geomorphological processes that are of relevance to urban marine ecology, weathering and rock coast geomorphology, and engineering. This thesis demonstrates the considerable potential to manipulate substratum-biota interactions on artificial structures for ecological gain, both directly and indirectly. More broadly, the explicitly interdisciplinary methodological approach adopted shows the value and necessity of integrated research for achieving useful, applied outcomes.