Biodiversity, function and resilience in biogenic shellfish reef management and restoration

Abstract

This thesis explores the potential effects of Ostrea edulis reef restoration on species diversity, a key focus of European coastal conservation initiatives: by first improving our ecological understanding of this rare biogenic reef habitat in terms of species diversity, function, structure and resilience and secondly benefiting restoration management by investigating the challenges of measuring restoration success. This thesis investigates the application of photogrammetry to quantify reef structural complexity, revealing fractal dimension as a strong predictor of biodiversity. Trait-based approaches reveal the differential ecological responses of epifaunal and infaunal communities to oyster presence, affirming O. edulis as an ecosystem engineer. Notably, the study challenges the assumed correlation between species richness and ecosystem resilience, highlighting that functional diversity can persist in less taxonomically rich assemblages. Overall, these findings underscore the importance of integrating biodiversity and functional diversity metrics in restoration projects, the challenges in using resilience as a success criterion, and the value of advanced monitoring techniques in improving the management and accountability of conservation projects. The work represents a series of the most widespread and detailed studies contributing to understanding the role of Ostrea edulis as an ecosystem engineer and the complexities involved in habitat restoration. Finally, this research can be used to set realistic goals for restoration management and for informing shareholders and funders.